Book Review: “The Story of the Cosmos.”

Putting God back at the centre of all things.

“In the beginning God created the heavens and the earth” Genesis 1:1. With majestic simplicity the author of the opening chapter of Genesis thus differentiated his viewpoint not only from the ancient creation myths of Israel’s neighbors, but also effectively from pantheism, such as is found in religions like Vedanta Hinduism and Taoism, or twentieth century process theology, and from polytheism, ranging from ancient paganism to contemporary Mormonism. The biblical writers gave us to understand that the universe had a temporal origin and thus imply creatio ex nihilo in the temporal sense that God brought the universe into being without a material cause at some point in the finite past.

William Lane Craig( pp183)

 

 

Title: The Story of the Cosmos, How the Heavens Declare the Glory of God

General Editors: Paul M. Gould & Daniel Ray

Publisher: Harvest House Publishers

ISBN: 978-0-7369-7736-4

Price: US $22.99/ UK £18.65

 

Eloquent, profound, powerful – here’s a beautiful and sweeping affirmation of God’s breathtaking creativity”

Lee Strobel, New York Times bestselling author of The Case for a Creator.

 

Contibutors: Dr. Luke Barnes, Dr. David Bradstreet, Dr. Brother Guy Consolmagno, Dr. William Lane Craig, Terry Glaspey, Dr. Paul M. Gould, Dr. Guillermo Gonzales, Allen Hainline, Dr. Holly Ordway, Daniel Ray, Dr. Sarah Salviander, Wayne R. Spencer, Dr. Melissa Cain Travis, Dr. Michael Ward.

 

Every now and then, a new book comes along which captures the essence of what it is to be an intellectually fulfilled Christian. Our Creator not only brought this Universe into being without a material cause, but also designed it with exquisite precision so that living creatures such as ourselves could explore its deepest mysteries through the media of science, art, music, poetry and fantasy literature. Using wonderful prose and beautiful illustrations, The Story of the Cosmos, sets a very high bar that will delight anyone who cares to read and consider its message. The central theme of the book is derived from the famous claim made by the Biblical King David, asserting that:

The heavens declare the glory of God; the skies proclaim the work of his hands.

Psalm 19:1

One of the most egregious claims made by modern expositors of scientific materialism(scientism) is that science and Christianity represent ‘non-overlapping magesteria,’ so that one system of knowledge cannot inform the other. Yet it is instructive to remind the Biblical ignoramus that to be a Christian is to value and seek truth. After all, did not our Lord remind us of such?

I am the way and the truth and the life. No one comes to the Father except through me.

John 14:6

So, simply put, to follow the truth is to follow Christ.

The Story of the Cosmos is the brainchild of an American school teacher and amateur astronomer, Daniel Ray, who managed to canvass the opinions of a stellar line up of Christian intellectuals across a dozen disciplines, ranging from theology to high-energy astrophysics. What unites all these authors is their passion for conveying the intellectual rigour of the Christian faith and how it inspired some of the finest minds in the history of human thought,  who clearly (and correctly!) viewed the created order as a manifestation of a mind infinitely more advanced than our own.

The book is divided into three parts;

I The Exploration of the Cosmos

II Expressions of the Cosmos in Art and Literature

III Evidences Pointing to the Creation of the Cosmos

 

In Part I, the authors explore the vastness, beauty and power of the cosmos and how these attributes provide solid clues to the nature of the Personhood who created it all. After a great opening chapter by Daniel Ray, laying the foundations of the themes to be developed in the book, Christian apologist and biologist, Dr. Melissa Cain Travis, makes a very powerful case for believing that the universe in which we find ourselves in is rational because its Creator(the God of the Bible) is also rational. Exploring ideas by Galileo Galilei, Johannes Kepler, Max Planck, Albert Einstein, Thomas Nagel and Alvin Plantinga, Travis, shows that naturalistic explanations of the origin and the Universe and life are almost certainly false. This is followed by a curious essay by planetary scientist and Catholic padre, Dr. Brother Guy Consolmagno, who reveals that science in general, and his study of meteorites in particular, is a way of “growing closer to the Creator.” Consolmagno’s work is a labour of love, he explains, where he is piecing together the exquisite machinery by which God created the worlds.

Studying the minutae of creation brings one closer to God, says Guy Consolmagno.

Part I continues with a highly entertaining essay by the professional astronomer, Dr. Guillermo Gonzalez, co-author (with Dr. Jay Richards) of the highly acclaimed book, Privileged Planet, demonstrating how our world shows the undeniable hallmarks of design but also goes further to show that where humanity finds itself on the outskirts of a vast spiral galaxy like the Milky Way, cannot be the product of idle serendipity, but rather must reflect the Creator’s desire for us to explore His creation using the methods of science and the high technologies we derive from it.

Following on from this, another professional astronomer, Dr. David Bradstreet, explores the majesty of the stellar Universe in all its diversity, focusing our attention on the light curves of a variety of eclipsing binary stars and how these allow him to get up close and personal with God’s illustrious creation. Bradstreet shows us clearly how stars evolve through time because there is a robust physical theory underpinning those claims, in contrast to Darwinian evolution, which is not entertained in this book (I’m guessing that all of the authors are now sceptical of those claims!)

Studying the light curves of eclipsing variable stars reveals the machinery of creation, according to David Bradfield.

Chapter 5 of Part I, written by astrophysicist, Dr. Sarah Salviander, presents a fascinating look at how the history of astrophysics and cosmology and their progress to becoming robust modern sciences, were often hampered by influential intellects who turned away from properly reasoned deductions just because it clashed with their world view. Salviander showcases the disputes that arose between Sir Arthur Eddington and his brilliant Indian graduate student, Subrahmanyan Chandrasekhar (Chandra). Although Eddington admired Chandra’s theoretical achievements, he refused to accept where his conclusions concerning the fate of massive stars (neutron stars and black holes in particular) would lead him. Salviander writes:

The answer is that Eddington fell victim to some combination of the four primordial barriers to understanding that are constantly at work in the minds of every person; limited perspective, misleading emotions, intellectual inertia, and excessive pride. Humans try to observe the Universe from the confines of the surface of Earth, which I can tell you from first-hand experience is always difficult. People find some ideas comforting and others disturbing, and those emotions often get in the way of the search for truth. Longstanding and popular ideas are often difficult to overcome even when compelling evidence like Chandra’s is presented. And, sometimes people like Eddington experience a lapse in humility that causes them to use their authority to oppose an idea they just don’t like.

pp 94-95.

 

Salviander also highlights the antics of the nuclear physicist, J. Robert Oppenheimer, who also went down the same road Eddington did.

“A close friend of Oppenheimer’s, the Nobel laureate physicist Isidor Isaac Rabi, believed that Oppenheimer’s abilities as a physicist suffered as a result of his turning away from the beliefs of the Old Testament in favour of the literature of Hindu mysticism. According to Rabi, Oppenheimer was scientifically blinded by an exaggerated sense of mystery and the boundary between the known and the unknown,  and became incapable of following the laws of physics “to the very end.” pp 95.

Salviander concludes that for many people, the Biblical God is “far greater, far more mysterious and uncomfortable even than black holes. We can’t see or touch God, but as with black holes, we have reason to believe something or someone immensely powerful is there. But for many people the notion of God is even more unsettling than black holes because anything with the power to create the universe has to be vast and powerful beyond our ability to imagine.” pp 105

In the final chapter of section I, physicist Wayne R Spencer, provides a historically accurate overview of the life and work of Johannes Kepler and Tycho Brahe, both devout Christians, whose talents and shortcomings as human beings often complemented each other. Far from “the boot camp mentality” of Protestant theology deliberately distorted by materialists like Carl Sagan in his best-selling book, Cosmos, Spencer clearly shows that these men considered astronomical discovery to be a powerful mechanism for better understanding the character of the Creator, who established all of the physical laws of the universe at the beginning of time.

Part II of the book kicks off with a wonderful essay by the American theologian, Terry Glaspey, who explores the relationship of art with the starry cosmos. As a scientist, I personally found this chapter to be fascinating and deeply enriching, as much of the content was previously unknown to me. Glaspey writes:

If the out-of-doors is a grand natural cathedral, then the artist can invite people who stand before their work to enter that cathedral, their brush-strokes pointing like fingers toward the glory of God to be found there.” pp 133.

Glaspey explains that while early Christian art concentrated on themes derived from the gospels, during the Romantic period(roughly the first half of the 19th century), “nature was widely embraced as the language of God.” pp 135

“Wanderer Above the Sea Fog” by Caspar David Friedrich(1818).

Glaspey proceeds to highlight some of the artistic works of various artists including Caspar David Friedrich(1774-1840), Thomas Cole(1808-1848), Fred Edwin Church(1826-1900), George Watts(1817-1904) and Vincent van Gogh(1853-1890).  According to Glaspey:

“...science and art are telling the same story about the mysterious glory of the cosmos……just two different ways of seeing the same wondrous things.” pp 147

Michael Ward, a professor of apologetics and Senior Research Fellow at Oxford, presents the next chapter of the book, which takes an in-depth look at arguably one of the greatest apologists for the Christian faith in the 20th century; C. S. Lewis, whose works of fiction and non-fiction address the Christian world view in all its richness.Ward explores Lewis’ circumspect interest in the development of science but who utterly rejected the notion that science was the only system of knowledge that can convey deep truths. In other words, Lewis was an admirer of science but strongly rejected scientism.

The next and final chapter of Part II, written by Dr. Holly Ordway, a professor of English, describes some of the work of another literary giant of the 20th century, J.R.R. Tolkien, whose many works of fiction also have a strong underlying Christian theme. But in this work, Dr. Ordway places a special emphasis on Tolkien’s lesser known work, The Silmarrion, and how its language and imagery is strikingly similar to themes developed in the Bible. As Ordway claims, “The Silmarrion is in many ways very much like the Old Testament. It is written in a formal, “high” register that evokes the language of the Bible….Linguistically, then, he provides us with the familiar made strange so that the strange has the potential to become familiar.” pp 179

The final part of the book looks at scientific evidences for God’s existence. The opening chapter, written by internationlly respected apologist, Dr. William Lane Craig, takes a close look at the doctrine of creatio ex nihilo and its centrality to the Christian faith. Although Craig is not a scientist, he nonetheless shows an excellent grasp of the conceptual ideas  developed by cosmologists over the years. Prior to the discovery of the expansion of the universe, many atheist scientists considered the universe to be eternal, with no beginning and no end, but after astronomers discovered several lines of evidence supporting hot Big Bang cosmology(red shifts of the galaxies, the cosmic microwave background radiation and the ratio of hydrogen to helium abundances that emerge naturally from hot Big Bang models), they were faced with the uncomfortable prospect(philosophically repugnant?) that the universe had a finite age, exactly as the opening line of the Book of Genesis claimed all along:

In the beginning God created the heavens and the earth.

Genesis 1:1

Lane Craig explains that attempts by atheist cosmologists like Lawrence Krauss to explain away the beginning, has been summarily rejected on both scientific and philosophic grounds. In his provocatively titled book, A Universe from Nothing, Krauss has a very odd idea of what ‘nothing’ entails, such that it is easy to see that the ‘nothing’ Krauss tries to pull over his readers’ eyes is actually something, whether it be a quantum field or some such. Indeed, Dr. Lane Craig, in perusing the many reviews of Krauss’ book, quotes the opinion of the distinguished philosopher of quantum physics, David Albert, who had the following to say regarding Krauss’ nothingness:

“….vacuum states are particular arrangements of elementary physical stuff…the fact that some arrangements of fields happen to correspond to the existence of particles and some don’t is not a whit more mysterious than the fact that some of the possible arrangements of my fingers happen to correspond to the existence of a fist and some don’t. And the fact that particles can pop in and out of existence, over time, as those fields rearrange themselves, is not a whit more mysterious than the fact that fists can pop in and out of existence, over time, as my fingers rearrange themselves. And none of these poppings….amount to anything in the neighborhood of creation from nothing…” pp 197

Indeed Albert concludes that “Krauss is dead wrong and his religious and philosophic critics are absolutely right.”

So much for a universe made out of nothing!

The next chapter, wriiten by physicists Dr. Luke Barnes and Allen Hainline, is particularly embarrassing for the High Priest of Darwinian pseudoscience, Richard Dawkins, who famously quipped:

The Universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but blind, pitiless indifference. DNA neither knows nor cares, DNA just is. And we dance to its music.

Barnes and Hainline walk us through the overwhelming evidence for fine-tuning evident at every scale from the sub-atomic world right up to the realm of the galaxies. Showcasing the various values assigned to the physical constants of physics, they show that only a very narrow range of those values are compatabile with life as we understand it. And those who wish to embrace the highly speculative ‘multiverse,’ must also concede that it too cannot avoid the issue of fine tuning.  Eventhough the authors do not bring God into the picture, their assessment of Dawkin’s bold assertion is clearly stated in their conclusion:

“This claim is false. A universe with, at bottom, no design and no purpose would be dead. Almost certainly. No structure, no useful energy, no galaxies, no stars, no planets, no chemistry, no complexity. Instead, as we look around us, we find a universe with something good at bottom: the capacity for life.” pp 219

 

The last chapter of the this section, composed by philosopher and Christian apologist, Paul M. Gould, describes the cumulative crisis in atheist material thinking as a kind of intellectual poverty that is dead to all that is beautiful, meaningful and awe-inspiring. In discussing what it means to be a being made in the image and likeness of its Creator, there are very strong motivations, Gould argues, to return to the “older, God-bathed and God-infused way of looking at the world.” More specifically, he argues that in order to be see the world accurately, we need to see it as it’s Creator(Jesus Christ) did.

“How does Jesus see reality? ” he asks, “As sacred. As a gift. As enchanted,” he asserts.

In perusing the writings of the other contributors to this book, Gould makes a persuasive case for believing that the physical attributes of this vast universe are such that they allow not only for human existence, but also for the flourishing of our kind as well as the other life-forms that inhabit our planet. He writes:

“A flourishing life is one in which the full assortment of natural capacities are activated, employed, and perfected. Plants have nutritive and growth capacities and a flourishing plant actualizes these capacities to realize its own good…..When it comes to humans we find a full panoply of capacities (in addition to growth and sensing) for reasoning, imagining, relating, acting, creating, moralizing, judging and more.Many of our capacities are not needed, at least not obviously, to the extent(in range and depth) for mere survival. yet we find those capacities present in us along with the general possibility of their actualization.” pp 230

Gould uses this line of reasoning as a platform to reject methodological naturalism in favour of theism. He continues:

“The following argument from fittingness helps us see the rational preferability  of theism to naturalism;

1. The fact that the universe is finely-tuned for the existence and flourishing of humans is not surprising given theism.

2. The fact that the universe is finely-tuned for the existence and flourishing of humans is surprising given naturalism.

3. Therefore, it is probable that theism is true.”

pp 232

In contrast, Gould considers evolutionary explanations for human flourishing as shallow at best and ill-thought through at worst. What is more, Gould asks a pertinent question:

“How can we recapture the Platonic-Aristotelian-Christian way of looking at things?”  pp232

Gould finds his answer in the revolutionary writings of St. Paul in 1 Corinthians:

“Paul helps us imaginatively understand the meaning of the universe. The hope of eternal life is pictured for us every day and night as we look around and see the immensity , beauty, diversity, and fittingness of creation. Just as the earthly and heavenly bodies each have their own splendor, so too(by analogy) will our imperishable bodies. Importantly, notice that the heavenly bodies – the Moon, the planets, the stars -perform for us a sacred duty, helping us to imagine a deep mystery, the mystery of our future ressurection in Christ.” pp 233.

Gould urges the reader to see the universe as God intended us to see it. All of reality is part of what Gould calls “God’s unfolding drama…. a drama in which everything fits together in order to display the manifold wisdom, goodness, and power of God, who is, “all in all“. pp 233.

The Story of the Cosmos ends with an afterword by Daniel Ray. The full glory of the night sky is the last great frontier which has been drowned out by light pollution from human designed cities. As a result the majority of people alive today never really see the full majesty of the stellar universe like our ancestors did. Ray suggests that we need to re-connect with this great wilderness in the sky in order to begin a journey back to our rightful place as the stewards of God’s creation. Watching the stars does not necessarily mean buying a telescope or any other optical device; we can use the eyes God gave us to watch the stars as they wheel across the vault of heaven. Like our forebears, we can study the stars to mark the progress of time and the march of the seasons, just as our Creator intended us to do.

The Scriptures quoted in the main text.

It was a great pleasure to read this beautifully composed work of Christian literature. It is thought-provoking, reverent and inspiring, with great apologetic appeal. In an insane world, where everything we once considered good and noble is being overturned by narcissistic, immoral, godless and aggressive secularists pulling the strings of government and poisoning the minds of our young people, The Story of the Cosmos is a refreshing oasis for the human soul, waiting patiently for the return of our Lord & Saviour, Jesus Christ.

 

Neil English is the author of seven books in amateur and professional astronomy.

 

 

De Fideli.

 

The War on Truth: The Triumph of Newtonianism Part II.

Taking the aperture advantage in grab ‘n’ go astronomy.

Continued from Part I

New entries indicated by ***

Of late I have been observing primarily with my 8” f/5.9 reflector.  After collimation, I check the seeing via visual observation at moderately high power on tight and/or magnitude contrast doubles—this is how I happened on this pair of doubles in Draco.

STT 312AB and STF 2054AB appear to the naked eye as the single star Eta Draconis.  Starting in Ursa Minor, a straight-line path from Kochab through Pherkad gets me to Eta as shown in the annotated Cartes du Ciel screenshot below.

 

DRADblDblPath_GIMP.jpg

 

I like to start with the fainter pair, STF 2054AB which is  a mere 12’ due North of Eta Draconis.  In 2017 this mag 6.2/7.1 pair had a separation of 0.943”, which is in line with historical speckle data.  At 345x, I saw two whitish stars of slightly uneven magnitude that were clearly split with dark space between the stars.  I gauged the seeing by estimating how often the image sharpens to two distinct discs.

The 2nd Ed. of CDSA lists STF 2054 as a (2) + 1 triple, meaning the A component is really AaAb.  Stelle Doppie informs the AaAb pair is CHR 138AaAb with a separation of 0.222” (1990)—perhaps those with larger glass can see this as oblong?

Moving on to the brighter object, Eta Draconis or STT 312 AB is where the fun starts.  This mag 2.8/8.2 pair has a separation of 4.68” as measured by Gaia satellite (2015.5)  Using the same eyepiece you used for STF 2054AB, try to find the faint secondary without prior position angle knowledge.  It will be quite small and about 4.5x farther than the distance between the stars comprising STF 2054AB. 

My first attempt at detecting STT 312 B required almost a half hour of moving my eye from averted to direct vision before I definitively saw the tiny speck of light corresponding to the companion.  On a subsequent night, I found the secondary right away because I knew where (and how) to find it.  The more steadily the diminutive B presents as a dot of light, the better my seeing.  Of course, darker skies will also aid your efforts for seeing the faint companion. 

STF 2054AB and STT 312AB help me gauge my local seeing and are fun to look at.  Have you looked at these stars lately?

Nucleophile(Austin, Texas, USA): from an online thread entitled, Fun in Draco: Proximal Pairs STT 312AB and STF 2054AB

Perhaps the aforementioned objects are too easy and you desire a greater challenge; if so, head about 11 degrees due south of Eta Draconis to Hu 149

This pair of ~matched magnitude 7.5 stars has a separation of 0.66″ (last precise in 2017 = 0.665″; my own measure in 2017 = 0.662″)  The pair are slowly widening:  Burnham (1978) lists the separation at 0.5″

Using my 8″ reflector, I observed this object last night and logged the following observations:

345x:  image transforms from elongated to notched (snowman) about 30% of the time; both stars are light orange-yellow

460x:  now seen as sitting on the border of resolved to two discs and split with the tiniest of black space between the discs

Below is an inverted image of Hu 149 I assembled in 2017 using my 15″ reflector and an ASI178MC camera at f/23 operating in mono mode.

 

HU149_JDSO.jpg

Nucleophile(Austin Texas, USA), from an online thread entitled; Fun in Draco: Proximal Pairs STT 312AB and STF 2054AB

Attached are some recent pictures of these double stars.  In all cases, N is up and E is left.

I obtained the images using my 15″ reflector and an ASI 290MM cooled CMOS camera.  An imaging train of Paracorr type 1 (setting 5), Powermate 2.5x and a Baader Orange filter gives an f ratio of 13.3  Images were collected using either SharpCap or Firecapture. 

Measures were made with Speckle ToolBox.  Composite images were assembled in Registax.

First up is STF 2054AB

STF2054AB_DRA.jpg

Dear Mark,

Thanks a lot for your interesting and well-documented presentation of a pair of doubles so well suited to gauging seeing  all year round. Last night I made these my first port of call with a 140mm Maksutov (an OMC 140 made by Orion UK, a good instrument). The physics suggest that the separation of 0.943” which you state for STF 2054AB is at the physical limit possible with this aperture, so I was keen to find out how I would fare.

The day had been hot, seeing was mediocre. I know from experience, though, that the air may calm down in certain phases of the evening, so I just hoped I would catch a good moment. At 75x I saw no hint of a companion of Eta Draconis, but STF 2054AB was definitely elongated. At 130x still no sign of Eta’s companion, but the elongation of STF 2054 became even more evident and it was clear at which end the weaker component stood. Encouraged by this, I went up to 210x. Now STF 2054 was a stretched figure-8 that popped apart into separate discs in better moments of seeing. Somehow quite charming!

I had gone in without PA knowledge and estimated this at 330°. Stelledoppie says 351°. So deviation <10%, that’s OK.

After having trained the eye in this manner, I turned my attention to Eta Draconis at 210x. All I could spot was a disc within a wildly dancing diffraction pattern. Although the B component, with its separation of 4.68”, is more than 4.5x further than the distance between STF 2054 A and B, it is evidently much harder to spot. This was an interesting lesson in the effect of Delta-Mag.

I find STF 2054 quite charming and Eta quite challenging, and will certainly be returning to them often. So thanks again, Mark.

CS, Christopher

C.Hay(Germany), from an online thread entitled; Fun in Draco: Proximal Pairs STT 312AB and STF 2054AB

Finally, here is Hu 149

I measured this one 21 times over three nights in order to gauge repeatability of the measuring protocol.  The current measure matches very well what I obtained a few years back.

Hu149_DRA.jpg

rugby, on 19 Jun 2019 – 06:11 AM, said:

I just finished observing STF 2054 AB and STT 312 in Draco using an  SW 120 ED and a Meade LX 10. A very bright moon with Jupiter brightened the eastern horizon.  Unfortunately these pairs lie directly above my house and thus suffer from heat rising from the roof.

What I saw was surprising. 2054 was elongated but not separated in the 120 at 200x.  I had not expected anything because it is on the edge of this scope’s capabilities. I did not try the 8 inch.

STT 312 AB was exceedingly difficult. Without prior knowledge of PA I kept seeing flashes of a tint dot south south preceeding the primary. I used the 120 at 200x. The view in the 8 inch was too turbulent for any resolution.

I am notoriousy poor in estimating position angle.

Hi Rugby,

Give ’em a try with your 8″–I think you will like the views!

Nucleophile( Austin Texas, USA), from an online thread entitled; Fun in Draco: Proximal Pairs STT 312AB and STF 2054AB.

Last night was about my 10th try to find that little bugger hanging out in the diffraction ring. I had tried repeatedly and without success with my 120mm ED. I’ve tried before with my 8″ [Newtonian], even on an EQ platform a few nights ago. This time I managed to see it with the 8″ at an ungodly 498x without the EQ, so constant nudging and then allowing it to drift (if the drifting was near rapids) . I would call it my “great white whale”, but it’s more like a tiny white pimple.

You’d expect the 8″ should easily split it, if I could just get improved seeing.

Chesterguy

Chesterguy( Stillwater, Oklahoma, USA), from an online thread entitled: Zeta Herculis…finally!

 

Well, I confirmed my sighting of Zeta Herculis las night. Same instrument, equal or better seeing and this time on my EQ Platform. Despite not getting my platform aligned perfectly on Polaris because it was blocked by my house, I still managed enough accuracy so that, while it drifted through the EP, it wasn’t like the prior night. Still a tough split at 498x in my typical seeing. I salute those of you who are splitting it below 140mm.

Chesterguy(Stillwater, Oklahoma, USA), from an online thread entitled: Zeta Herculis…finally!

I observed this double with the 8″ reflector twice in recent days:

345x:  just split with smaller secondary appearing yellow against bright white primary; secondary appears to be sitting between first and second diffraction rings

314x:  when seeing permits, the yellowish secondary is seen sitting atop the primary

I did a few Aberrator simulations for the expected view using either my 8″ or 15″ reflectors; these are shown below.

 

ZetHERAberrator_Gimp.jpg

The 8″ inch simulation is fairly close to what I saw.  The 15″ simulation shows the secondary now sitting near the second diffraction ring.  In some images I obtained recently with the 15″ and an ASI 290MM camera this is pretty much what I saw.  In the composite image below the first diffraction ring appears as a fuzzy halo while second ring got washed out a bit in processing.

 

STF2084_Zeta_HER.jpg

Nucleophile(Austin, Texas, USA), from an online thread entitled; Zeta Herculis…finally!

I just made a 7 inch aperture stop today for my 18. Worked great tonight. I’ve made them many times before but it’s been a while. Seeing tonight was so good the better views were at full aperture..

Darren Drake(Chicago, USA), from an online thread entitled Aperture Mask

DavidC, on 19 Jun 2019 – 03:41 AM, said:

I am making an off axis aperture mask for my 10 inch lightbridge, but using a single 4 inch hole. I got the idea from san francisco sidewalk astronomers, but they had it as plans for a solar filter. I’m making it for planets and double stars. I’ve been told by stepping the aperture down to 4 inches, planets won’t be as bright, therefore I can use more power on them. At 1270 mm focal length, I’m hoping for impressive views on planets by using more power. Am I thinking this correctly?

 

Thanx, David

Waste of time IMO. I have a 10” LB with a very good mirror set. I also have excellent 100 and 120 mm ED refractors. If seeing is equal, the 10” reflector slaughters the excellent refractors in planetary detail.

SteveG(Seattle, Washington, USA), from an online thread entitled: Aperture Mask

Vla, on 20 Jun 2019 – 2:55 PM, said:

Smooth edges have more of a cosmetic effect. Rough edges don’t induce aberrations, because they don’t affect wavefront shape, and unless the edge is ridiculously rough, the diffraction effect will be negligible. As an illustration, effect of a 2-inch focuser protruding into the light path of a 200mm diameter mirror. As much as 1 inch into the light path will take only about 1% of the energy out of the central maxima (which, expectedly, becomes somewhat elongated, because the vertical mirror diameter is effectively shorter).

Yes indeed! The effects are diffractive and tiny, not what we optics guys call aberrations. I also like your focuser signature there… Fourier Transform (impulse-response) says it all.

Masks roughly-cut with scissors or a knife are perfectly fine. The one thing to try to avoid is long straight edges. Those will give noticeable spikes. The three straight edges of the focuser there… do a little bit of that.

On the tech/theory side… there are infinitely many wavefronts that will produce the same impulse response. That’s because the sensor (eye or camera) detects only amplitude, but not phase. So you can’t inverse-transform back to the wavefront by processing on the one image of a star… unless you use two or more (ideally many) focus positions’ images. And that is what we call ~phase diversity analysis~ (what was used to assess Hubble’s flaw). And what is implicitly involved in the various casual ~Sar Tests~ that we often talk about here. 

Tom Dey(Springwater, New York, USA), from an online thread entitled: Aperture Mask

Deep13, on 14 Dec 2018 – 06:56 AM, said:

In my mind, the ideal planet telescope is a 10 or 12″ EQ Newt (split ring?) in a permanent location with a clear view of the south and overhead. Add a good binoviewer, pairs of long ZAOs, and an easy way to reach the EP, and I’d be all set. In reality, it would be too expensive and I have no place to set it up permanently. So-o-o-o, I’ve arranged to buy a used 8″ f/8 EQ-mounted Newt. I’ll need to have some servicing done on the mirrors. I’m thinking that within the realm of likely possibility, this may very well be my ideal set-up. Right now it has no fan and a tall R&P focuser, so I may change those things. And I’ll built a cart for the Meade RG mount. I already have a tall adjustable chair and a Denk II with pairs of TV Ploessls.

 

Any thoughts? What’s your ideal planet scope?

 

I had both a very good 8″ Zambuto f-7.5 and a 10″ Waite f-5.8 on an EQ mount, the 8″ I had rotating rings but still a very big pain in the rear to use on an EQ mount. I am considering a slightly different set up 10″ f-5.3 through f-5.5 for a shorter tube and mounted on an EQ-AZ mount, in AZ mode viewing will be far more easier as the EP will be on one side and accessible.  At the focal lengths mentioned as long as you get a premium mirror and build it well you can achieve 50x per inch with sharp image on the planets, and you can use a 1.83″ secondary, CO 18.3%. good luck.

dag55(Hamburg, Illinois, USA), from an online thread entitled; Ideal Planetary Scope

The Orion 4.5 in f/8 dobsonian could be an option. Seems to get good reviews on the optics here on CN. Lightwieght. I believe the focuser is plastic, but, it should be ok with normal weight 1.25in eps.If the moon with a 4 -5 in reflector is the ojective, this little scope should do a decent job.I have not used the Orion, however, I do have a 4.5in f/8, and I think they are capable little scopes.

Good viewing,

dmgriff, from an online thread entitled, 4-5” reflector recommendation

 

+1 on the AWB OneSky.

I was surprised at how well it works. At 14 pounds total, it might be just what you’re looking for.

Havasman( Dallas, Texas, USA), from an online thread entitled: 4-5” reflector recommendation

The AWB One Sky is fine for the money but its burdened with an very poor helical focuser, preferable is the Lightbridge 130 , discontinued but still available from some dealers, the Zhumell 130, the best of the bunch IMHO or the slightly smaller Zhumell 114 , very similar to the Orion Starblast but less money, the Zhumell is also sold as the Edmund Astroscan Millenium, D.

Binojunky, from an online thread entitled: 4-5” reflector recommendation

 

The Onesky is a fine scope. I have no problem with the focuser.,and the mount is quite stable.,Some of my best spent astro money.,cheers.,

Attached Thumbnails

  • 20190327_183143.jpg

 

Clearwaterdave(Western Maine, USA), from an online thread entitled: 4-5” reflector recommendation

How is a 4″ apo a “no brainer” when the OP specificly asked about a reflector? The OP has other scopes and seems to have some idea of what he’s lookin for.,What scope you think would do a better job for doubles or planets is not what he asked about. If you have used and liked a 4-5″ reflector of any type and you want to share your experience here that would be helpful to the OP.,waytogo.gif

Clearwaterdave(Western Maine, USA), from an online thread entitled: 4-5” reflector recommendation

I have had the OS up next to a 102ed and “to my eyes” the views are too similar for me to say either one was “better”.,And there are many many very happy OS owners.,So yes.,you can expect a quality reflector for $200.,That’s the no brainer.,and the OS isn’t the only one.,there are a few good quality 5″ reflectors out there for $200.,YOMV.,

Clearwaterdave(Western Maine, USA), from an online thread entitled: 4-5” reflector recommendation

Thank you again for all the great responses. I’m always pleasantly surprised at the information you guys have and your experience. Yes, optics are my primary concern for the scope, but I haven’t really read one bad review concerning them so I think the OneSky is what I’ll go with. I have a pretty large back deck with a decent view to the south so it will be easy to track the moon every night, even if only for a few minutes. Concerning refractors: the truth is I have little experience with them (I know they’re not hard to figure out) and my comfort level, if you will, is with Dobsonian type reflectors. I have a neighbor down the road who has a 4” Takahashi (I think), and the views through it are really something else. Then he told me the price tag and my mind went to how how big of a Renegade or Teeter I could get for the same price. Plus someone told me that owning a refractor will lead you down to the perilous and very expensive road of astrophotography.
The reason I don’t put the 8” out on the back deck is that I use it specifically for planetary viewing now. I have it in the garage ready to load up for a quick drive into the foothills next to the house. The view is better and I get away from all the house and street lights. At f/7 that 8” gives just wonderful views of the planets. I was also able to complete the AL double star program with. If you haven’t looked at that program, I recommend it as it was one of my favorites to do. The 8” was the first scope I ever owned and I had to rebuild it out of disassembled parts, which I found at a flea market. That was a journey, let me tell me you. But now it’s dialed in with a great mirror and I’ll have it forever.
And with the 10”: that’s my deep-sky, dark site, fall into the heavens scope. I try to get out there at least once, if not twice, a week. It too has great mirror and makes it hard for me to financially justify a larger scope given there’s so much to see with it.
Back to the OneSky. Hopefully it will be what I’m looking for. I have perfect cover and place for it, it won’t get dirty, and when I’m out enjoying the late evening and want a quick peak, it’ll be right there.

Mick Christopher, from an online thread entitled: 4-5” reflector recommendation

One of my all-time favorite 4ish inch scopes is the Orion XT4.5, mentioned by Dave and Ed earlier. It’s a very nicely engineered and accessorized product, and provides sharp high power views with very minimal focus wiggles and immediate dampening times. The long focal length makes the scope forgiving of the somewhat imprecise focuser, which works quite well. It’s also very easy on simple eyepieces, which is handy. It’s not a do-all scope, owing to the focal length and 1.25″ ep limitation, but it’s still capable of providing pleasant low power views, yet shines at moderate and high powers. Add a 5 gallon bucket, inverted, as a “chair” (which can pull double duty as a caddy for charts, ep case, and binos) , and the scope works well for adults without the need to raise the scope on a platform.

KerryR( Midwest Coast, Michigan, USA), from an online thread entitled: 4-5” reflector recommendation

 

If the OP can handle the extra size and cost the Orion XT6″F8 is a fine scope, I picked mine up last years for $300 Canadian brand new shipped to my door, take it out in two pieces, plonk it on the ground and away you go, D.

Binojunky, from an online thread entitled: 4-5” reflector recommendation

 

This report is the third installment of a series of observational investigations I have made using an 8 inch f/5.9 reflecting telescope. 

Check out this link for goals and methods used in this study:

https://www.cloudyni…-and-monoceros/

Corvus
Bu 920 (12158-2321) mags 6.86/8.22; pa = 308°; sep = 1.934”, 2016 (solid data)
345x:  well split with secondary a bit smaller; both stars are yellow; well above resolution limit

B 1716 (12247-2004) mags 9.42/9.42; pa = 230°; sep = 0.701”, 2014 (solid data)
345x:  single star
460x:  a bit elongated, but never resolved despite best efforts; below resolution limit; important data point to set lower limit for fainter stars

Hydra
STF 1273 AB, C (08468+0625) mags 3.49/6.66; pa = 310°; sep = 2.824”, orbital estimate for 2019.3 (solid data)
345x:  easily split to two yellow stars of widely varying magnitude; above resolution limit

Bu 587 AB (08516-0711) mags 5.75/7.41; pa = 121°; sep = 1.186”, 2017 (solid data)
345x:  blur of light that sharpens to a small secondary that is just split
460x:  spit 100% of time; above resolution limit

Bu 219 (10216-2232) mags 6.70/8.52; pa = 186°; sep = 1.773”, 2015.5 (Gaia DR2, solid data)
345x:  split 100% of time; secondary is much smaller and both stars are white; above resolution limit

A 3064 (08403-1518) mags 9.15/9.00; pa = 357°; sep = 0.681”, 2015.5 (Gaia DR2, solid data)
345x:  just resolved to two tiny discs 40% of time; just above resolution limit; important data point to helps set minimum value of rho for faint, equal mag pair

A 338 (08207-0510) mags 8.83/9.39; pa = 17°; sep = 0.569”, 2015.5 (Gaia DR2, solid data)
345x:  slightly pointy
460x:  slightly elongated, but never resolved; well below resolution limit

HJ 4478 (11529-3354) mags 4.67/5.47; pa = 52°; sep = 0.578”, 2015 (data needs confirmation)
627x/orange filter:  elongated that becomes notched 10% of time; just below resolution limit; difficult due to low altitude; requires re-measure to firm up separation value

B 1175 (10582-3540) mags 8.25/9.23; pa = 251°; sep = 0.61”, 1998 (data is old, scant)
345x:  resolved 50% time to two similar magnitude yellow stars; a bit above resolution limit; separation likely greater now; requires newer measures of separation and delta mag

B 218 (12002-2706) mags 9.11/9.69; pa = 340°; sep = 0.472”, 2015.5 (Gaia DR2, scant data)
627x:  very faint; rod shaped at times, but no hint of resolution or notch; well below resolution limit; requires re-measure to firm up separation data

HWE 72 (12136-3348) mags 6.48/8.55; pa = 159°; sep = 1.231“, 2016 (solid data)
345x:  just split 30% of time to two white stars; secondary is much smaller; above resolution limit

Bu 411 (10361-2641) mags 6.68/7.77; pa = 303°; sep = 1.33”, 2017 (solid data)
345x:  just split 100% time to two light yellow stars of somewhat dissimilar magnitude; above resolution limit

Bu 219 (10216-2232) mags 6.70/8.52; pa = 186°; sep = 1.773”, 2015.5 (Gaia DR2, solid data)
345x:  split 100% time; secondary is much smaller and both stars are white; above resolution limit

Leo Minor
STF 1406, aka STT 211 (10056+3105) mags 8.37/9.42; pa = 219°; sep = 0.728”, 2017 (solid data)
345x:  just split from resolved 30% time; stars are faint, white, and seem to be of similar magnitude; above resolution limit; a newer delta mag measure desired

Lynx
STT 159AB (06573+5825) mags 4.45/5.50; pa = 236°; sep = 0.704”, orbital estimate for 2019.3 (solid data)
345x:  single star
460x:  possibly pointy
627x:  at times elongated showing secondary as smaller, but never resolved; below resolution limit; it is unclear why this is so difficult—perhaps there is a ‘brightness’ factor that needs to be incorporated?  Revisit next year using orange filter and get a new measure.

COU 2607 (07441+5026) mags 5.33/8.43; pa = 164°; sep = 0.973”, 2012 (data is a bit old but is considered solid)
460x:  secondary pops into view as just split 50% of time; just above resolution limit

STT 174 (07359+4302) mags 6.62/8.26; pa = 92°; sep 2.170“, 2015.5 (Gaia DR2, solid data)
345x:  split 100% of time; both stars are white and secondary is much smaller; fine mag contrast double; well above resolution limit

Hu 850 (08094+3734) mags 9.42/9.23; pa = 349°; sep = 0.57“, 2016 (scant data)
345x:  viewed for an extended period of time using averted vision shows the pair exhibiting a notch just past extended a mere 10% of the time; never resolved and is considered below the resolution limit; a re-measure of separation is needed

Ursa Major
STT 232AB (11151+3735) mags 8.02/8.90; pa = 243°; sep = 0.623”, 2015.5 (Gaia DR2, solid data)
552x (Pentax 2.5XO/Paracorr Type 1, setting 1):  pointy about 25% of time, but never a hint of being resolved; below resolution limit

STT 235AB (11323+6105) mags 5.69/7.55; pa = 44°; sep = 0.949”, 2019.3 (orbital estimate, solid data)
345x:  on the resolved/split border with secondary seen as much smaller
460x:  cleanly split; primary is yellow, secondary is light orange; above resolution limit

STF 1770 (13377+5043) mags 6.93/8.18; pa = 128°; sep = 1.722“, 2015.5 (Gaia DR2, solid data)
345x:  cleanly split; primary is light yellow while the smaller secondary is light orange—a fine pair; above resolution limit

STT 200 (09249+5134) mags 6.53/8.57; pa = 337°; sep = 1.251”, 2015.5 (Gaia DR2, solid data)
345x:  close split (AV helps to see fainter secondary)
460x:  easily split to two stars of unequal magnitude—very nice; above resolution limit

STT 232AB (11151+3735) mags 8.02/8.90; pa = 243°; sep = 0.623“, 2015.5 (Gaia DR2, solid data)
552x (Pentax 2.5XO/Paracorr Type 1, setting 1):  pointy about 25% of time, but never a hint of resolution; below resolution limit—important data point for calculator development

A 1346 (09591+5316) mags 8.84/9.66; pa = 179°; sep = 0.624“, 2019.3 (orbital estimate; data is incongruent between orbital estimate, historical speckle and Gaia DR2)
345x:  slightly elongated; very difficult
460x:  moves past elongated to notched <10% of time
627x:  possibly seen as resolved 10% of time with averted vision; just below resolution limit; requires re-measure to firm up separation value

STT 229 (10480+4107) mags 7.62/7.92; pa = 254°; sep = 0.63“, 2019 (estimate from 4th Interferometric Catalog; data incongruent between historical speckle, orbital estimate and last precise)
345x:  moves past pointy to resolved 30% of time showing secondary as a bit smaller versus the primary
460x:  persistent snowman shape that sharpens to nearly split 30% of time; just above resolution limit; re-measure of separation needed for this important data point

Bu 1077AB Dubhe (11037+6145) mags 2.02/4.95; pa = 336°; sep = 0.802“, 2019.4 (orbital estimate, solid data)
460x/orange filter:  very difficult; secondary pops into view 30% of time as just split—otherwise, it is merely a blur of light/brightening of first diffraction ring; at or just above resolution limit

**Have you observed or imaged any of these objects recently?  Let me know.  Perhaps you have a suggestion for a double I should observe—I’m all ears!

Nucleophile(Austin, Texas, USA), from an online thread entitled; Investigations With an 8 Inch Reflector. Part I: Canis Major, Canis Minor, Lepus, and Monoceros

My preference is in the “or” category. I have used all of my scopes for doubles, but I love my 10 inch reflector… it is a double star magician… except for Sirius B… just can’t get that one in the 10 inch. But I have split it ONCE with my 4 inch achro (retired this one to give to my granddaughter)… she loves doubles too…

SeaBee1, from an online thread entitled; scope preference for doubles

I use my Stellarvue 105mm APO most of the time for doubles wider than 1″ and when the seeing is only fair.  It gives such nice images with no central obstruction.

If the seeing is above average I use the Intes 180mm Mak-Cass with its astro-sital 1/9 wave optical system on the tighter doubles, and planets.

I don’t usually use the 10″ LX 200 on doubles, but one night when the seeing was very good I was using the Baader 8-24 zoom on the double double in Lyra and zoomed all the way to 660x,  the stars looked perfect and the separation was enormous.

I usually don’t use my 18″ Obsession for doubles, but once while doing a two star alignment on Antares with my 12.5mm cross-hair eyepiece, there it was a bright orange star with a little green orb next to it.  I hade to just stop and take a good long look, it was beautiful, and so was the seeing that night.

Astromaster; from an online thread entitled; scope preference for doubles

Last seen this star for a long time. Seeing that the closer stars that I knew are either already inaccessible (too close) or have gone beyond the horizon, I decided to observe those that are less mobile. In particular, this one. Since there are days with an excellent atmosphere and they should be used. In comparison with the double in the zet boo, this star looks obviously wider and accessible. It is interesting that the difference in the sizes of fragments of diffraction disks is visible. This is quite unexpected, considering that the difference in brightness is only 0.2. Maybe this star is variable? and therefore I see that parts of diffraction discolves of different sizes (this happens when the difference in brightness is more than 1 … 1.5 magnitudes). This is weird.  I used a large piece of paper to accurately mark the track of the star and its position. Such dimensions allowed me quite accurately, without using devices, to note how exactly the disc is stretched..eta crb1.png
Constantin 1980, from an online thread entitled: Observation Eta CrB (0,38 “) 9\04\2019

This report is the fourth installment of a series of observational investigations I have made using an 8 inch f/5.9 reflecting telescope. 

Check out this link for goals and methods used in this study:

https://www.cloudyni…-and-monoceros/

Bootes
BU 224 (14135+1234) mags 8.94/9.35; pa = 95°; sep = 0.65“, 2015 (last precise; not solid, opening)
345x:  single star
460x:  pointy but never resolved; well below resolution limit; magnitude data is from Hipparcos (1991, 515nm); needs a re-msre of delta mag and separation

 

STT 287 (14515+4456) mags 8.40/8.62; pa = 5°; sep = 0.575“, 2017 (last precise vs 0.659” orbital estimate for 2019.3; data incongruent)
345x:  seen as elongated 30% of time
460x/averted vision/extended viewing:  elongated only, never resolved; below resolution limit; needs a re-msre of separation

 

STF 1866 (14417+0932) mags 8.48/8.65; pa = 205°; sep = 0.733“, 2015.5 (Gaia DR2, solid data)
345x:  on the border of resolved and split to two even magnitude light yellow stars; above resolution limit

 

STF 1863 (14380+5135) mags 7.71/7.80; pa = 60°; sep = 0.654“, 2017, (last precise, solid data)
460x/orange filter/averted vision/extended viewing:  moves past elongated to resolved 20% of time
627x/orange filter: just resolved 50% of time; just a bit above resolution limit; important data point (equal mag pair) to set minimum value of rho

 

STF 1867 (14407+3117) mags 8.36/8.83; pa = 355°; sep =0.674“, 2017 (data needs confirmation)
460x:  just split 50% of time to two white stars of slightly dissimilar magnitude; need re-msre of separation

 

A 148 (14220+5107) mags 8.32/8.96; pa = 190°; sep = 0.535“, 2019.3 (4th Int. Catalog estimate vs 0.58” last precise in 2015; data not solid)
627x:  a bit elongated but never resolved; well below resolution limit; need re-msre of separation

 

KUI 66 (14148+1006) mags 5.44/8.43; pa = 111°; sep = 0.99“, (my own measure in 2017 with ASI 178MC camera; data tentatively considered solid as it is a match with 4th Int. Cat. estimate)
627x/orange filter:  much smaller secondary seen as a resolved dot very near first diffraction ring 30% of time; just above resolution limit; important, large delta mag data point so re-msre with ASI 290MM camera needed.  See image below.

 

AGC 6 (14339+2949) mags 9.81/10.30; pa = 133°; sep = 0.752“, 2015.5 (Gaia DR2, solid data)
345x/extended viewing:  seen as elongated rod, never resolved; very faint and difficult; below resolution limit; important data point to set ‘faintness factor’

 

STT 298AB (15360+3948) mags 7.16/8.44; pa = 187°; sep = 1.208“, 2019.4 (orbital estimate, solid data)
345x:  easily split to two small light yellow stars of similar magnitude; very pretty; above resolution limit

 

A 1110AB (14497+0759) mags 7.69/7.93; pa = 245°; sep = 0.692“, 2015.5 (Gaia DR2, solid data)
345x:  oscillates between resolved and split; both stars are yellow with secondary seen as smaller and *delta mag is likely >0.24
460x:  seen as split 100% of time with secondary possessing a hint of orange; above resolution limit; Gaia DR2 gives a delta mag of 0.67 which does not agree with Tycho value of 0.24—will attempt a measure of delta mag to rectify

 

Canes Venatici
STF 1606 (12108+3953) mags 7.44/7.93; pa = 145°; sep = 0.611“, 2019.3 (orbital estimate vs 0.627”, last precise in 2017; data not solid)
460x:  elongated but never resolved
627x:  moves past notched rod to resolved 20% of time; at or just above resolution limit; observation supports tighter value of rho [0.611”]; this is an important data point; will re-msre (possibly annually) to firm up value

 

STT 251 (12291+3123) mags 8.35/9.27; pa = 61°; sep = 0.781“, 2017 (last precise; data not solid)
345x:  just resolved 30% of time with secondary much smaller
460x:  just split 50% of time; a bit above resolution limit; faint secondary plays role in difficulty; re-msre of separation needed

 

STF 1768AB (13375+3618) mags 4.98/6.95; pa = 95°; sep = 1.656“, 2019.3 (orbital estimate; solid data)
345x:  well split, primary is white and secondary is light yellow and considerably smaller—a fine sight!  Above resolution limit

 

Coma Berenices
STF 1639AB (12244+2535) mags 6.74/7.83; pa = 324°; sep = 1.855“, 2019.3 (orbital estimate; solid data)
345x:  well split, primary is white and secondary is light yellow; very pretty mag contrast pair; above resolution limit

 

STF 1687 (12533+2115) mags 5.15/7.08; pa = 200°; sep = 1.18“, 2018 (last precise; solid data)
345x:  a bit past just split 100% time with secondary noticeably smaller; both stars are yellow; above resolution limit

 

COU 397 (12575+2457) mags 9.06/9.71; pa = 63°; sep = 0.70“, 2015 (last precise; solid data)
345x:  single star; faint!
460x/averted vision:  slightly elongated but never resolved; below resolution limit; important data point to establish ‘faintness factor’

 

A 567 (13328+2421) mags 6.21/9.71; pa = 256°; sep = 1.450“, 2015.5 (Gaia DR2, solid data)
345x:  secondary seen as split 50% time and appears as very small, very faint dot a bit past first diffraction ring of primary; above resolution limit

 

Ursa Minor
STF 1989 (15396+7959) mags 7.32/8.15; pa = 23°; sep = 0.67“, 2013 (last precise vs 0.603”, orbital estimate for 2019.4; data not solid)
345x:  moves past elongated to exhibit a snowman shape
460x:  resolved about 40% time with secondary a bit smaller; above resolution limit (observation supports separation closer to 0.67” value; re-msre of separation needed)

 

BU 799AB (13048+7302) mags 6.60/8.45; pa = 265°; sep = 1.39“, 2017 (last precise; solid data)
345x:  easily split; both stars are white and secondary is considerably smaller—very pretty; above resolution limit.

 

A 1136 (16135+7147) mags 9.22/9.47; pa = 9°; sep = 0.727“, 2007 (last precise, data is old)
345x:  barely split; both stars are very small and white, and secondary is just a bit smaller; helps to establish ‘faintness factor’; above resolution limit; a re-msre of separation is needed

 

Virgo
BU 797AB (12345+0558) mags 9.10/9.39; pa = 146°; sep = 0.61“, 2010 (last precise, data is a bit old but considered solid)
345x/averted vision/extended viewing:  slightly pointy
460x:  elongated and on the border of resolved, but never did resolve despite an extended view
627x:  moved past elongated to resolved about 5% of time; at or slightly below resolution limit; a very important data point that warranted 45 mins of study under very good seeing conditions

 

RST 4484 (11447-0431) mags 8.46/8.39; pa = 64°; sep = 0.738“, 2017 (last precise; data not solid)
345x:  just split to two ~even magnitude yellowish-white stars—beautiful!  Above resolution limit; re-msre of separation needed

 

BU 935AB (13459-1226) mags 5.66/8.47; pa = 304°; sep = 1.03“, 2001 (last precise; data is old)
460x:  brightening of first diffraction ring sharpens to much smaller secondary 30% of time; both stars are yellow; above resolution limit; a new measure of separation is needed for this important mag contrast binary

Have you observed or imaged any of these objects recently?  Let me know.  Do you have a suggestion for a double I should observe within one of these constellations?  I would like to hear about it.

Nucleophile(Austin, Texas, USA), form an online thread entitled, 8 Inch Reflector Investigations. Part IV: Bootes, Canes Venatici, Coma Berenices, Ursa Minor, and Virgo

Here is an image of KUI 66 I obtained in 2017 using an ASI178MC camera operating in mono mode.

 

KUI66_JDSO.jpg

Cool, another crop! Here’s some of mine for comparison:

STT 287, 552x 12.5”. Wow! Hair-split, ~0.7″, near equal or half a delta mag.

STF 1867, 552x 12:5”. 0.5 delta mag, hair to figure 8 split, white. Not especially good seeing

Kui 66: 12.5” Unresolved faint haze at 553x, but adding the apodizing mask I had a glimpse of the B star 15% of the time, very small and faint, ~3″ and 4-5 delta mag. Both orange. Definitely there.

STT 289: 8″ 205x: Noticed a very much fainter star emerge with averted vision then could hold direct. Very fine, well split. 8″ 410x: Tried to bring out the B star with higher magnification, but oddly it disappeared. Curious. 20″ 410x: B star easily seen though the disks are bloated, seeing not good.

STT 298. 12.5” 552x Wow! Almost didn’t look at this one since it was split in the 80mm finder. One component is a close equal pair, ~2″.

STT 251. 12.5” 553x: Decidedly not round disk — there’s also a brightening in the diffraction — but not really split.

STF 1768: 8″ 205x: Very tight pair, a little more than hairline split, ~2 delta mag. 8″ 333x: white and dull blue, ~1″, split, Nice!

STF 1768. 12.5: 553x: Very pretty pale yellow and orange, 2-3 delta mag, ~2″

STF 1639: 8” 205x White and slightly blue pair; close, around 3″ [overestimated the split, it was so clean!]

STF 1687: 12.5” 553x = 35 Com: Bright orange & fainter B, showpiece, ~1.5″

A 567: 12.5” 553x: very faint B, very close, ~1″ when seeing stills, 3-4 delta magnitude. Surprised it is not so difficult. B looks like it doesn’t have any light of its own and is illuminated by A.

BU 935 = 86 Vir: 12.5” Pretty orange star but @ 553x poor seeing won’t allow split of 3 delta mag, 1.2″ B.

mccarthymark(San Francisco Bay Area, California, USA), form an online thread entitled; 8 Inch Reflector Investigations. Part IV: Bootes, Canes Venatici, Coma Berenices, Ursa Minor, and Virgo

Excellent info, Mark.

my notes on your notes:

a.  STT 287, inclined to think it is tight–like 0.6″  I will def msre next year.

b.  the much studied KUI 66, nice use of mask to glimpse the companion!  I used an orange filter and very high power on an excellent night

c.  STT 289–I will add this large delta mag object to my list (thanks!)

d.  STT 298AB  something is askew here with the delta mag as both of us describe the mags as being similar–I didn’t catch this first time around but have made a note for next year to try and get a msre of delta mag for this one; I looked back into my log notebook and also noted:  “tiny headlights; beautiful!”  Additional note based on the 4th Int Cat.:  the same year as the Tycho mag values [as listed in the WDS] are those from Hipparcos (albeit at a slightly shorter wavelength = 511nm) which found  the magnitudes to be 7.59 and 7.78–a much closer match to what we observed.  This is humorous:  WDS notes say the ‘D’ component at 167″ is actually a galaxy (possibly a quasar)!  How’s that for ‘optical illusions’  At mag 14, I will be chasing that one for sure with the 15″ scope.

e.  STT 251 was surprisingly difficult for both of us…

f.  BU 935  you may wish to give this one another shot on a night of very good seeing; it is difficult

Nucleophile(Austin, Texas, USA), form an online thread entitled, 8 Inch Reflector Investigations. Part IV: Bootes, Canes Venatici, Coma Berenices, Ursa Minor, and Virgo

Here is a composite image of A 1110AB taken in 2017 with the ASI 178MC camera.  The image supports a delta mag of >0.24

My measured value differs quite a bit from that of Gaia DR2 (0.692″) for this object.

 

A1110AB_JDSO.jpg

Nucleophile(Austin, Texas, USA), form an online thread entitled, 8 Inch Reflector Investigations. Part IV: Bootes, Canes Venatici, Coma Berenices, Ursa Minor, and Virgo

    So much for Newtonians not being suitable for observing high-resolution double stars eh?

    Mr. Hardglass

     

    Sol, that the primary is 8.38″ in diameter is a revelation. I assumed it was the standard 7.9″. When I stow it away for the monsoon, I need to measure it. That’s kind of cool, but definitely non standard for a Newt, yea? I wonder if they are using 8″ SCT blanks that are (supposed to be) a little bit ‘over sized’. Just curious.

    When I do the math for a 2.6mm diagonal support, I get 2.6/8.38 = 31% obstruction. Not a ton of difference, but comforting to some. My MCT has a 30% +/- obstruction and offers no ill feelings. The images are nice. It should have the contrast of a 8.38 – 2.6 = 5.8″ refractor, and you do not hear folks complaining about those views. It still puts ~90% of the maximum light into the Airy disc compared to a perfect 5.8″ APO. It’s right at the diffraction limit with a descent (not premium) mirror.

    Abytec(Pampanga, Philippines), form an online thread entitled: ES Firstlight 8inch dob vs. Skywatcher 8inch dob

    Actually I took lots of measurements regarding the E.S. 8, and measured many times. Not because I was obsessively compelled to, but I had an opportunity to acquire another 8″ mirror with a “pedigree”. So I needed to know if I would be able to use the E.S with little if any modification for an actual 8″ diameter with a traditional 1.4″ thickness to work.

    To the original O.P. the stock E.S. primary is also 7/8″ thick so the 6 point floating cell is just another little plus for the E.S. over the GSO or Synta.

    With the stock E.S. 8 that’s well collimated and cooled Jupiter showed a bit better than TEC140 with really good, (8P) seeing. On D.S.O. no contest.

    Sol Robbins(astronomical author and distinguished sketcher), from an online thread entitled, ES Firstlight 8inch dob vs. Skywatcher 8inch dob

    Hi all,

    Please find attached a drawing of Jupiter I made last night with my 8 inch Newtonian in my home observatory.  I have to say, I was quite impressed with image quality- the details on the disk were easier to see despite the low altitude of the planet.  The main feature was the dark and turbulent SEB(s), and the start of the STropB in the South Tropical Zone.  The EZ was rather active as was the NEB, the NTB and NNTB contained darker sections.  Io is shown in the drawing and was probably the strongest colour I have ever seen, no doubt this is due to the low altitude.

    Best wishes,

    -Paul

     

    Jupiter_2019-06-29-0012UT_visual_PAbel.png

    Paul G. Abel(author, BBC Sky at Night presenter, Leicester, UK), form an online thread entitled: Jupiter and Io last night.

     

     

    From practical experience I have found optical quality, coating quality, proper baffling and eyepiece used more important to contrast than CO size once its below around 30%. Why small APO’s out perform slightly larger obstructed scopes is usually NOT due to being un obstructed but optical quality, mechanical quality and other factors. A smaller CO is nice, but can limit your fully illuminated field and eyepiece choice. Theory is great, but assumes everything is equal which it seldom is.

    The biggest enemy of contrast is scatter, stray light and optical quality if you have a reasonable size CO.

    Richard Whalen(Florida, USA), from an online thread entitled, Secondary Mirror Obstruction?

    TOMDEY, on 02 Apr 2019 – 9:46 PM, said:

    A six-inch scope with a 30% diameter obstruction resolves far better than an unobstructed five-incher. Just generate the non-normalized point-spreads and MTFs to see that in action!

     

    PS: This is why a (good) modest-sized Dobsonian will always blow the socks off a good smaller refractor (any smaller refractor!) for both light-gathering and resolution!

     

    But, gota admit… refractors make fine finder scopes on big Newtonian reflectors…    Tom

    Every time I see yet another thread about secondary mirror sizing and central obstruction (particularly when the MTF graphs start appearing), I say what Tom said above – just use a slightly larger telescope and don’t worry about it.  (And those little refractors do make very nice finder scopes.)

    However, I will also add something else – if you undersize the secondary or size it to only fully illuminate the very center of the field, then you are:

     1) using the part of the secondary that is most likely to have a defect,

     2) using the part of the secondary that might roll off due to cooling,

     3) using the part of the secondary that is often left out of the interferometric analysis, and

     4) forcing yourself into very precise placement of the secondary in order to get something close to a fully and symmetrically illuminated field (in other words, making it very hard on yourself for very little gain).

    My method to size secondaries for most telescopes is simple – add 4″ to half the mirror’s diameter to get the intercept distance.  Then divide by f/#.  Then go up one flat size if the calculation yields a size that is close to a standard flat size.

    So, if I calculate that a 3.1″ or 3.2″ flat is needed, I go to 3.5″.  At 3.4″ – 3.5″, go up to 4.0″.

    The 4″ added to half the mirror’s diameter just allows the use of a filter slide underneath a properly placed SIPS or Paracorr 2.  For a little more breathing room, use 4.5″ in the calculation.

    Try this on various commercial Newtonians and you’ll find that some have secondaries that are too small…..

    Mike Lockwood(premium large aperture mirror maker), from an online thread entitled, Secondary Mirror Obstruction?

    Whew! for my 36-inch F/3.75… that comes out to (18+4)/3.75 = 5.9″ … and mine is 6.25″, with a nice wavefront! And, frankly… even a tad bigger than that might be prudent. I just happened to already have the 6.25 and characterized the wavefront at work… figured a known good one would keep the project hustling along!  I then teased the focuser as close in as possible… reducing that four inches to about three. When I focus my farthest-innie eyepiece… only have a few mm to spare! 

    Tom Dey( retired optical scientist, Springwater, New York, USA), from an online thread entitled, Secondary Mirror Obstruction?

     

    A number of factors are working against reflectors:

    1. Reflectors have central obstructions, which reduce the resolution.There’s also a bit of loss to the spider, which creates diffraction spikes.

    2. Reflectors tend to have problems with temperature differentials within the tube, which creates air currents that distort the image.

    3. Mirrors have more scatter than lenses.

    4. Reflectors have a harder time staying in alignment than refractors.

    5. Reflectors have coma. Refractors have their own problems (chromatic aberration and spherical aberration) but expensive glasses and lens designs can basically eliminate these.

    6. Refractors are usually higher end than reflectors (so, they tend to be higher quality).

    However, you can usually resolve these:

    1, 3. Reflectors scale up far better than refractors, so they can have more aperture, which helps compensate for these problems. Obstruction sizes can be minimized, curved spiders will spread the diffraction spikes around and make them less apparent.

    2. Intelligent fan usage can do a lot for air current formation. Good telescope design can keep cool-down times reasonable and mostly eliminate this issue in use.

    4. It’s pretty easy to get good at reflector collimation. Just keep it collimated.

    5. Coma can be mostly eliminated through use of a paracorr. Or, you can use a longer focal ratio.

    6. There are premium mirror-makers who produce mirrors up to the quality of the best lenses.

    If you resolve these issues, reflectors still do not perform up to the standard of a refractor of the same aperture – but will perform as well as a refractor that is slightly smaller. However, you can get a reflector that is far larger than any refractor you can get. It’s reasonably feasible to get a 12-16″ dobsonian with premium optics and good thermal management, and that will (under good conditions) walk all over any refractor anyone with a normal income will ever be able to afford.

    Mitrovarr(Boise, Idaho, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    Refractors typically do not suffer from thermals, are typically in excellent collimation, are baffled better, and don’t have a center obstruction.

    The number of reflectors that are miscollimated is astronomical. So overall I think you have a better chance of having a excellent experience with a large APO refractor. BUT, find a 10″ or bigger 1/6th wave or better, perfectly collimated reflector and it will knock your socks off.

    Whichwayisnorth(Southern California, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    That Dalek, on 03 Mar 2017 – 01:35 AM, said:

    Just a question that came to me. Thanks for any answers!

    Refractors often have better definition, which is the ability to show fine, low-contrast detail.  A reflector solves that problem by being larger, gathering more light and having higher resolution.

    A old rule of thumb is that a 6-inch Newtonian, properly designed and built, will beat a 4-inch refractor.

    Caveman_Astronomer, from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    I will simply say that what we perceive as “sharpness” is not resolution.. A few comments, experiences, thoughts.

    – If I look at 52 Orionis, a 1 arcsecond double star in my 120 mm Orion Eon. It is very close to the Dawes limit so on a perfect night, the disks are overlapping and its difficult split at best. If I point my 10 inch F/5 Dob at 52 Orionis on that same night, and the scope is cooled and of course collimated, 52 Orionis is split wide open. Much smaller disks widely separated.

    In this case, I see 52 Orionis as much sharper in the 10 inch.. But most often, I think the comparisons of both contrast and resolution are made in relative terms, at a 0.5 mm what do I see?

    – Looking at the Globular M79 in Lepus is a 6 inch refractor versus my 22 inch Dob, few would perceive that the refractor was sharper.. M79 in the 22 inch looks about like M13 in a 10 inch. M79 in a 6 inch looks, well we know what it looks like..

    – Reflectors are fininky to the uniniated.. They require care and attention.. Collimation and thermal management are important..

    It always seems there comparisons are made between some sort of ideal refractor and the average faster Newt. An 120 mm F/5 achromats versus a 130 F/5 Newtonian.. I think most would (f)ind the Newtonian sharper…

    Jon Isaac(San Diego, California, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    mogur, on 04 Mar 2017 – 02:19 AM, said:

     

    dugpatrick, on 03 Mar 2017 – 01:53 AM, said:

    All good points.  But, yes, resolution is better with larger aperture.  An 8″ newt will have better resolution than a 4″ APO. And better CA.

     

    Doug

    Only if it’s PERFECTLY collimated! (a rare find) And I’ll take a little CA over loss of contrast because of a spider vane and secondary obstruction.

     

    Perfect collimation of reflectors is not hard to obtain, with the right tools (Glatter laser + TuBlug or Catseye cheshire + autocollimator).   But not every reflector owner is so demanding of collimation, nor willing to spend for the top-level tools that reliably produce perfect collimation.  OTOH, others of us are a bit happily OCD about collimating our reflectors.

    FirstSight(Raleigh, North Carolina, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    Apo refractors exist in a sweet spot where their unobstructed aperture and single-pass light path tends to produce better images than similar aperture reflectors in the same seeing conditions. Most amateurs view with seeing conditions that put anything larger than about ten inches at a disadvantage because the scope resolution is limited by the seeing, not the aperture. With steady seeing and constant temperatures (e.g. Florida) reflectors can do just as well as apo refractors for visual use.

    GJJim, from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    mogur, on 04 Mar 2017 – 02:19 AM, said:

     

    dugpatrick, on 03 Mar 2017 – 01:53 AM, said:

    All good points.  But, yes, resolution is better with larger aperture.  An 8″ newt will have better resolution than a 4″ APO. And better CA.

    Only if it’s PERFECTLY collimated! (a rare find) And I’ll take a little CA over loss of contrast because of a spider vane and secondary obstruction.

     

    The difference in inherent resolution between an 8-inch scope and a 4-inch scope is so vast that the Newt would have to have disastrously poor optics or be really badly collimated to flunk this particular test.

    Operating at the magnifications useable in a 4-inch APO, the loss of contrast due to the 8-inch Newt’s central obstruction is barely detectable.

    Tony Flanders(Former Sky&Telescope Editor, Cambridge, MA, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    osted 04 March 2017 – 08:23 AM

    Mitrovarr, on 04 Mar 2017 – 04:26 AM, said:

     

    grif 678, on 04 Mar 2017 – 03:43 AM, said:

    In all my old books, way back before APO’s and SCT’s. the rule of thumb seemed to be, in all instances, that a 3 inch refractor was about equal to a 6 inch reflector. I often wondered why, since a 6 inch mirror had so much more area than a 3 inch lens, but I guess the focal length and secondary obstruction had something to do with it.

    I wonder if that figure was due to worse coatings back in the day. I really wouldn’t expect a modern 3″ refractor (any kind) to beat a 6″ of equivalent quality. Even back in the day, I’m not sure. I have a really good long 3″ achromat and a good 6″ homemade (not by me) dob, both are at least 30 years old, and the dob totally destroys the refractor on planetary detail.

    I think one only has to setup and RV-6 alongside a 3 inch F/16 achromat to see that even 50 years ago,  a 6 inch Newtonian was far more capable than a 3 inch refractor… 

    Been there,  done that,  know the result,  don’t need to do it again.. 

    Jon Isaac(San Diego, California, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    We can confidently say that a well-made 4-inch refractor can do better than a well-made 4-inch reflector, but the issue gets a little murkier when we start looking for a refractor that is a serious competitor for a well-made 12-inch Newtonian, for example, or even for a well-made 8-inch Newtonian.

    Caveman_Astronomer, from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    So there I am with my 120 mm F/7.5 Orion Eon with the FLP-53 doublet that cost me $1200 used and next to it is a 10 inch F/5 Dob that cost me $240 used.

    Splitting doubles, the 10 inch does the number on the refractor, viewing Mars, the 10 inch does the number on the refractor. This should be no surprise. This does require an operator who knows how to clean a mirror, the collimate a scope, to cool a scope.. And it does require decent seeing..

    Inch for inch, there is nothing as potent as a small refractor.. Dollar for dollar, pound for pound, reflectors offer more planetary contrast, will split tighter doubles..

    Jon Isaac(San Diego, California, USA), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    Refractors are great. Too bad they are all so small in aperture

    Caveman_Astronomer, from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    caveman_astronomer, on 04 Mar 2017 – 1:40 PM, said:

     

    Cpk133, on 04 Mar 2017 – 1:25 PM, said:

    God, or natural selection, depending on your persuasion, seems to favor refractive optics for wide fields, low maintenance, and the sharpest views per mm of aperture.

    What kind of refractor should I buy that would compete with a 12-inch Newtonian?

     

    This 10″ refractor should do the trick.  http://www.cloudynig…nch-tec-at-wsp/

     

    $50 000 + $15 000 for the mount and $8 000 for the tripod.

     

    Cotts(Madoc, Ontario, Canada), from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    russell23, on 04 Mar 2017 – 3:24 PM, said:

     

    treadmarks, on 04 Mar 2017 – 3:14 PM, said:

    People often say refractor images are more “aesthetically pleasing” (sharper?) even if they don’t show more detail. Aside from the quality issues mentioned, I’m thinking it’s also because smaller telescopes are more resistant to bad seeing. My understanding of the theory is that larger telescopes can have better contrast through brute-force, by having more clear aperture. So it’s not the contrast giving refractors more aesthetic images, it’s their smallness and the fact that refractors take the most advantage of that smallness.

    That certainly could be part of it.  Another factor for me is the simplicity of the observing.  I am able to sit at the back end of the scope and sight along the tube to locate objects or stars for star hopping.  The viewing is always comfortable like that and sighting along the tube with your eye next to the eyepiece is not as easy with a newt.

     

    Like I said – I’m not ant-Newtonian.  I might even look to pick up a large dob when I retire.  But for now I’m very happy with what I have.

    I think a Newtonian is actually easier to point.  Imagine an object 75 degrees elevation.  With a refractor,  it is very awkward to position my head to look along the tube or through a red Dot or Telrad finder.  With a Newtonian,  the focuser and finders are at the sky end of the scope,  I just lean over,  glance through the Telrad,  point the scope, comfortable and effective. 

    Jon Isaac(San Diego, California, USA) form an online thread entitled, Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    Quote

    I don’t even use a finderscope with my refractor.    The first thing I did when I bought the 120ED was sell the finderscope.     My widest TFOV eyepiece serves as my finderscope.  Sometimes that is the 40mm Pentax XL (2.8 deg TFOV).  Sometimes that is the 32mm plossl, 32mm Brandon or 28mm Pentax XL (1.6 deg TFOV).  Or if I’m feeling really interested in a challenge I might even use the 12mm XF or 9mm Morpheus (0.77 deg TFOV) and go sweeping for the target.    I sight along the tube to locate stars to starhop from or a lot of times I just point the OTA right to the location of the target.   I find it remarkably efficient.

    Like I said,  I can make it work..  You talk about spending more time observing the object,  working a list of double stars at 60 degree elevation with a 50 mm RACI finder is much more efficient than awkwardly sighting along the tube,  and then using a wide field eyepiece to locate the object.. 

    With my short focal length refractors,  I generally just shoot from the hip..  But there is no doubt,  the Dob  with the Telrad and RACI finder is much better for easily finding more challenging objects. 

    Jon Isaac(San Diego, California, USA) form an online thread entitled, Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

     

    Richard Whalen, on 04 Mar 2017 – 6:14 PM, said:

    Planets, brighter DSO objects or the moon in high contrast the refractor can be the best choice.

    After more than 50 years observing, I find the aesthetics of the view more important than the brightness. Also part of the experience for me is also sitting out under the stars on a perfect night and seeing the silhouette of that long white tube against the background of a sky full of stars. Somehow it’s how it should be, and all is right in my world.

    I know what you mean; there’s something about those grand old 6-inch achromats on their massive German equatorial mounts that sends a chill down the spine. The views are incredibly clean, and the scopes are big enough to yield some very detailed views of the planets — but just barely big enough.

    The fact remains that a 12-inch Dob is far cheaper and more portable than a long-focus 6-inch achromat. And while its aesthetics may be lacking, on a good night it can deliver far more planetary detail than said achromat.

    Tony Flanders(Cambridge, MA, USA), form an online thread entitled, Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    mlbex, on 17 Mar 2017 – 6:34 PM, said:

    When is the last time a major observatory built a refractor? As far as I know, the largest refractor still in use is the 36-incher on Mt Hamilton, built in the 1880s (according to Wikipedia)! It’s still a fine telescope, but there’s a reason observatories are building reflectors. Perhaps they scale better. That wouldn’t really be a problem with everyday astronomers.

    Yes, reflectors scale vastly better, for several different reasons. To be precise: false color scales linearly with aperture, large lenses are hard to support, and the glass for a lens has to be perfect throughout its thickness rather than just at the surface. And this is indeed an issue for everyday backyard astronomers.

    Refractors pretty much rule supreme in apertures smaller than 90 mm. There are some pretty good 76-mm Newtonians on the market, but they’re only marginally cheaper than equivalent reflectors, and they have a number of disadvantages. So they appeal mainly to people who are really hard-up for money. There are also a handful of Mak-Cas scopes in apertures of 60 or 70 mm, but since the main benefit of that design is small physical size, and 60- or 70-mm refractors are already quite small, the tiny Mak-Cas’s aren’t very popular.

    Refractors are also quite competitive in apertures from 90 to 125 mm. But toward the top of that range, the disadvantages of the design are beginning to kick in big-time. At 125 mm, either you end up with a short-focus achromat with tons of false color, or a long-focus achromat that’s really unwieldy and hard to mount, or an apochromat that costs a minor fortune.

    At 150 mm, refractors are really a stretch. Very few people can afford apochromats in this size, and with achromats you typically end up with both lots of false color and an unwieldy size. There are nonetheless some people who love 150-mm achromats because of their low light scatter, but that’s truly the end of the line. Refractors bigger than 150 mm (6 inches) are rare indeed in the amateur world.

    With reflective designs, by contrast, you’re just getting started at 150 mm. That’s considered quite small for a Newtonian, and not quite there for an SCT. Eight-inch Newts are really cheap and effective, especially on Dobsonian mounts, and eight inches is the standard size for SCTs.

    In the modern world of amateur astronomy, where deep-sky objects are the most popular targets, even 8 inches isn’t much. That’s barely enough to resolve most globular clusters or see the spiral arms of the biggest and brightest galaxies. So while refractors certainly have their place for viewing wide fields, for viewing the planets in less-than-perfect seeing, and above all for photography, the fact that they scale up poorly definitely limits their popularity among amateur astronomers.

    Tony Flanders(Cambridge, MA, USA), form an online thread entitled, Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    Newtonians, provide a natural, simple viewing position for the eyepiece at all apertures. Refractors and Cassegrains require tall tripods and star diagonals. We’re not going to make the artificial distinction and comparison between 90mm refractors and 90mm reflectors or between any other refractors and reflectors that happen to have nominally matching apertures.

    Caveman_Astronomer, from an online thread entitled; Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    Redbetter, on 20 Mar 2017 – 10:30 AM, said:

     

    caveman_astronomer, on 18 Mar 2017 – 1:17 PM, said:

     

    Newtonians, provide a natural, simple viewing position for the eyepiece at all apertures.

     

    An equatorial Newtonian appears to have some rather unnatural eyepiece positions depending on the declination of the target and the position on relative to the meridian.

    No, I’d say that if an equatorial-mounted Newt has rotating rings, it’s always easy to find some comfortable viewing position regardless of where the scope is pointing.

    However, I don’t really agree that Newts provide the best viewing position regardless of aperture. I do agree that alt-az mounted Newts (including Dobs) have the best ergonomics of all designs up to a focal length of around 1,500 mm, maybe even to 2,000 mm. But beyond that, they start to require increasingly tall ladders, which begin to get genuinely dangerous and/or scary around 3,000 mm. In those focal lengths, I think that Cassegrain designs are quite clearly superior, due to the fact that you’re observing from the bottom of the tube and the fulcrum is closer to the back than the front.

    Refractors certainly have the worst ergonomics, at least in focal lengths above 1,000 mm. They really have the worst of all possible worlds: bottom viewing, long tube, fulcrum far from the eyepiece, viewing angle exacerbates variation in head height rather than counteracting it as with a Newtonian.

    Tony Flanders(Cambridge, MA, USA), form an online thread entitled, Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    I’ve just recently got myself my first refractor (a 120mm f5 achro) after having used an 8″ f6 dob my whole life. I was actually quite surprised to find the ergonomics much worse and I have had to constantly adjust the height of the tripod to find a good position. Despite this, observing close to the horizon for long periods of time seems quite awkward for the neck.

    Olle Erikkson(Sweden), form an online thread entitled, Why are refractors considered to be sharper than reflectors if resolution is a function of the aperture?

    300x in an 8 inch is a 0.7 mm exit pupil or about 37.5x /inch. Even my 70 year old eyes can view the planets at magnification levels and more, provided the seeing supports it.

    I consider 300 x fine for an 8 inch..

    Jon Isaac(San Diego, California, USA),from an online thread entitled, 8″ F/5 Newt planetary and coma

     

     

    Richard Whalen, on 09 Jul 2019 – 04:34 AM, said:

    How much magnification you can use depends on your optical quality, seeing and your eyesight and aperture. With my 8″ scope I am often around 350x to 450x on Jupiter, and 525x on Saturn. Sometimes higher when conditions are perfect.

     

    My rule of thumb is 43x the aperture in inches on a very good night with decent optics, higher for very good or excellent optics. Also much depends on which planet you are observing.

    Richard, I am usually between 333x and 400x on Jupiter in my 8″, as well, at 0.6mm and 0.5mm exit pupil. I find 333x (~40x per inch) power to be the most productive and my rule of thumb, as well. At 400x, Jupiter is still workable, but it’s beginning to dim a little. I was looking at Oval BA the other night, it was easy at 333x. I could see it at 400x, but not as easily.  And I am fairly sure at 500x it would have been even more difficult. I accidentally pulled out the wrong eyepiece and hit 1200x once (0.16mm exit pupil!). Not much to see up that high. I guess my optics are not that good. smile.gif

    I get that the quality of our optics produce nice sharp and high contrast images at high power, after all it’s the same quality image we see at less magnification where (lack of) aberration is apparent in terms of resolution and contrast. But I am always interested in the mechanism of how high quality optics can afford higher magnifications at vanishingly small exit pupils, say a bit smaller than 0.5mm, without excessive image dimming. At some point we begin to lose visual sensitivity and, thus, lose the image itself as the eye is working at a very small relative aperture (less than about 0.5mm f/60).

    Getting closer to 600x on Jupiter, IME, is unworkable (or at least not as productive as a bit less magnification) in any 8″ aperture even in good seeing. I mean, we can still see some detail up that high, I saw some detail at 1200x, too. Just not much detail was perceived by the eye, even though we are viewing the same fine afocal image we observed at 400x and less. At some point, it becomes less about the optics and more about the exit pupil and, I suspect, throughput as well.

    For example, Jove is fine on both 6″ Mak and 8″ Newt at 0.6mm exit pupil, (240x and 333x, respectively). But, at 0.5mm exit pupil, the Mak image is unworkable while the Newt image still had some legs. I suspect this has something to do with the throughput of each scope, not so much about their respective quality or difference in aperture. Of course the 8″ image is brighter, thus affording higher magnification than the 6″. They are pretty close to the same level of quality, not premium but pretty good and roughly the same obstruction. Both were thermally stable and well collimated. Seeing varied from above average to very good in both over time.  (I agree with you in another thread when you talked about stray light control and mechanics, too.) 

    But, when I hear folks talk about quality optics affording higher magnification, I am always reminded of the small exit pupil involved and how quality might over come the inverse square law and our own personal level of acuity (as a variable). Unless you or they mean magnification higher than say 1mm exit pupil when poor optics start to become visually and visibly soft, while better optics retain their fine imaging properties until the image surface brightness is no longer supported at smaller exit pupils. Sometimes when folks talk about ludicrous magnification in any scope, and especially in premium scopes, I wish they’d elaborate on what they saw up that high. Tight double stars or a bright planetary nebula? 

    I just do not understand how quality affords higher magnification to smaller than 0.5mm exit pupils (very small relative apertures) and well above the magnification where poor image quality becomes apparent. 

    Asbytec(Pampanga, Philippines), from an online thread entitled, 8″ F/5 Newt planetary and coma

    After 500x the image starts to get too dim in a 8″. This is where a 14.5″ shows it’s stuff at 1000x on Jupiter.

    Chas, I know you have great seeing. My seeing is pretty much the same during our dry season monsoon. So, yea, we’re operating at higher magnifications, generally, and on Jupiter, specifically, as well as other objects. I guess that is the crux of my question. Assuming descent optics in both, the 14.5′ at 1000x is about the same as an 8″ near 550x. In my experience with an 8″, the image is less productive starting about 400x and above. Others may vary somewhat, of course.

    Unless the optics are truly better in the 14.5″ in appropriately good seeing. Then my question is why can the higher quality, larger 14.5″ aperture show it’s stuff at much higher magnification than roughly the equivelent of an 8″ showing it’s stuff at 400x? The equivelent magnification in the 14.5″ would be about 750x, but why does quality allow it to show it’s stuff at 1000x (equivelent of 550x in the 8″)? I’d love to know what can be seen up that high because, my thoughts are, the 14.5″ image is dimming, too, for the same reason the 8″ is already dimming at 400x and higher.

    I’ve seen the Jovian image at 500x and 600x in the 8″, but I would not call it really a great image (on the eye, anyway). There is some detail to be seen, still, and the limb appears to be as sharp. But, a lot of the lower contrast detail is becoming or is already difficult to see. Bright high contrast stuff like double stars are no problem, but Jove is a different animal. It cannot be pushed to ludicrous magnifications, but if it can and optics are the reason, then my question is why and what is seen up that high. A sharp limb, a few belts, the moons, and maybe the GRS?

    Asbytec(Pampanga, Philippines), from an online thread entitled, 8″ F/5 Newt planetary and coma

    My lifetime-best view of Jupiter in the 12.5″ was at 456x (36.5x/inch), and we could see a knotty white swirl in the salmon colored (then, now it’s more orange) GRS.

    The whole disc looked like the surface of an orb, not a flat disc, and the colors were amazing–ochers, pale ivory, bluish tints, grey-greens, reds, whites, blacks, greys, etc.

    It was a technicolor image, and super-sharp–sharp enough we could see the shadows of projections on the cloud banks below. And an 18 element stack of lenses in the focuser.

    Spectacular seeing conditions, obviously.

    On other nights of superb seeing, I’ve gone as high as 986x (79x/inch), just to see if it could be done, but I haven’t been able to see what I saw that night.

    The moral of the story is that it is not only optical quality, but seeing that determines how high a magnification we can use.

    In absolutely perfect seeing, I’ve used a superb 7″ scope at 160x/inch and the image was OK. I just couldn’t see anything in that scope at 160x/inch

    that I couldn’t also see at 100x/inch, though the image of Saturn at 1123x was incredibly large.

    But even after all the crazy high powers, give me 400-500x with spectacular seeing, and I can see details on Ganymede and Neptune. 1000x isn’t really necessary.

    It’s all about the seeing.

    Starman1(Los Angeles, California, USA), from an online thread entitled, 8″ F/5 Newt planetary and coma

     

    The short answer is that a good Premium telescope will probably perform noticeably better than an average cheap mass-marketed one. Somewhere between better and way better. But that’s actually a statistical statement. Occasionally a too-good-performing cheap one somehow slips through their QC system… and occasionally a Premium scope will be deficient. The Premium scope is almost always worth the Premium price differential. That is to say — if you don’t want to mess around — just buy the better scope and enjoy it! 

    Tom Dey(Springwater, New York, USA), from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    I owned a Synta 8”f6 Dob along with a custom 8”f6 Dob with a Zambuto mirror for several years. The differences in the views were subtle, requiring side-by-side viewing on rare nights of excellent seeing to confirm. On the other hand, the improvements in the views offered by two inches additional inches of inexpensive aperture were obvious.

    If an 8” scope is the largest you want to handle, and you want improved views, premium 8” optics will provide a marginal improvement at about 10x the cost. An inexpensive 10” scope will cost about 2x and the improvements in its views will be obvious. However, premium scopes usually come with premium mechanics in addition to premium optics, and the mechanical improvements are usually obvious under all circumstances.

    So, my preferred approach these days is to empirically determine the largest scope that I am comfortable using at an observing site, and then upgrade or replace its optics and mechanics as much as my budget allows

    Gwlee, from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    Make sure that “1/10 wave Peak-to-Valley” rating is on the wavefront, not the mirror surface. Also, make sure the seller has a good reputation.

    I went a different route, and had my first Synta 8″ F/6 mirror re-ground by a respected glass-pusher, as its initial figure was quite poor. To fill in the gap while this was in process, I purchased a second Synta 8″ F/6 (yeah, seems like a stupid idea, but the second one was reasonably good). The total cost was lower than buying a complete specialist-built scope, but of course I had to do a little work myself.

    I’ve decided to hold onto both scopes for now. I’ve set up the one with the great mirror using a better mirror cell, low-profile focuser, and smaller secondary, optimizing it for high magnifications, while the second scope is for lower mags, with a larger fully-illuminated field.

    Like you, an 8″ Newtonian is at my limit for weight and size.

    Hoawardcano(Olathe, Kansas, USA), from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    Starlease, on 19 Jul 2019 – 7:44 PM, said:

    Put a Zambuto mirror in my 10″ dob and it outperformed my 14″ claimed 1/8 wave dob for planetary details seen. Little tiny details on Mars seen in 10″ were invisible in 14″.

    Your 14″ dob at 1/8 wave is about 1/4 wave at the wavefront – just diffraction limited. It’s possible in extremely good seeing that your 10″ would show more detail, but on an average night I doubt it, unless there are other issues that you haven’t thought about like cooldown, collimation, mounting of optical components, or maybe the claim of diffraction limited of the 14″ isn’t true.

    People are always looking for fairy dust they can sprinkle into their telescopes to make them defy the laws of physics. Someone let me know if it works. smile.gif

    Nirvanix(Medicine Hat, Alberta, Canada), from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    Replacing the 2ndry will probably be the best bet

    but you should learn how to star test 

    https://youtu.be/QxUQJjjsdW4

    Pinbout(Montclair, New Jersey, USA), from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    Although I didn’t do it with 8″, but with 10″, I think the mirror exchange was a large improvement for visual observations. Views through my GSO 10″ were good, but star tests have shown some astigmatism. Following the advice on this forum, I exchanged the secondary mirror for Antares, but the astigmatism was still there. So, I decided to exchange the primary for the 1/10 pv. The difference is considerable. With GSO mirror, the views were very good, now they are great. I can see many more crispy details on Jupiter, Saturn, Mars or the Moon. Things that were ‘soft’ before are sharper now. And it happens even on the nights with poorer seeing, I just have to wait for the moment in between smile.gif

    For low-power, wide-field DS objects, probably there is no difference, but color: GSO coating produced a greenish touch, OOUK makes it more white/ flat.

    With GSO mirror, I often used the aperture mask to see planets sharper. After exchange, in my opinion the aperture mask only makes things dimmer and less sharp, so I guess the scatter light before was bigger with the standard mirror. 

    Overall, I have learnt the lesson saying that the exchange for a better mirror was worth it, the telescope is used now more often for the sheer joy of visual hunt for details.

    WOJ2007(Tychy, Poland), from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    After owning a really fine 8” CZ mirror for several years I am always impressed by the views when the mirrors are properly collimated and when the primary mirror has reached thermal equilibrium. Is it better than a mass market 8”? I can’t say because I have no way to compare. It’s also really light for the given aperture (better construction/thinner mirror) without giving up stability.

    What I can say about my premium reflector is that the mechanicals beat the pants off my venerable, but flawed 10”. The focuser, balance, bearing smoothness, primary mirror cell, secondary mirror holder are superior in every way. The entire tube is flocked and the cradle design allows the tube to be easily turned and/or moved north south. My definition of a premium scope (which includes the mirror) is one that both offers expected mirror performance while the structure disappears as one uses it. A premium scope is more than a premium mirror and a premium mirror will fall short of full potential if one has to battle with the other parts.

    Chesterguy(Stillwater, Oklahoma, USA) from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    I have two 8ers to compare, one Zambuto 8″ F7, the other a generic “Skywatcher” 8″ F6.

    But the comparison is necessarily through memory . . .

    I visit family a couple of times per year in Australia. Got tired of lugging my C6 and refractor through airports. So last time back I bought an 8″ F6 “Saxon”, which is the same as the Skywatcher 8″ solid tube.

    About a year ago I came across an ad where a guy had the parts for an 8″ F7–the primary being a Zambuto quartz, and the secondary a 1/30 wave Antares. Moonlight single-speed focuser. A solid tube (flocked), and splashed out for an Aurora precision cell. I run it alt-az on a Skytee 2 mount.

    How do they compare?

    I wasn’t expecting miracles with the Saxon. A solid diffraction limited scope was all I was wanting.

    First object was Sirius at high elevation in quite good seeing. Within 2 minutes of setting up the scope on first light I easily split the pup. Done. This is a good scope!

    Star test isn’t perfect (I am no expert on this). My recollection was a brighter ring on the outside on one side or the other of focus. So I’m guessing a less than perfect edge. But it performs very well indeed, and more than met my hopes. I haven’t spend much time on planets with this scope (it does perfectly fine). When down under I’m more interested in the Southern objects–Magellanic clouds put up a ton of detail in this scope.

    But what about that Zambuto? Well, as far as I can tell it is as close to perfect as you can get in an 8″ mirror. Star test looks identical to my eye on either side of focus.

    The mirror is up and ready to go with just a couple minutes of running a fan, and puts up etched views of the planets and moon (it has a very small secondary, and is optimized for planets). A particularly memorable view was of the double double from Mt Pinos (parking lot must be close to 8k ft). Perfect dots and diffraction rings. An observing friend with a lot of experience called it the best view of the double double he’d ever seen.

    But how would this thing compare to a 10″. Well, I think you’ll get a more sharp/contrasty view out of the 8″ premium, but so long as the 10″ is decent, it will resolve more detail, those details will just look a tad softer.

    Areyoukiddingme, from an online thread entitled: Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

    N3p, on 19 Jul 2019 – 5:57 PM, said:

    Has anyone replaced their regular 8″ Synta Newtonian with a higher quality 8″ Newtonian and how was your experience?

    The key difference I found was as follows.    During critical observation of an object for 5-10 mins, on the couple of times when the atmospheric seeing snapped into focus- lasting 0.5 to 2 seconds- the mass market mirror would give an “ooh nice” response whereas the premium would give a “wow!” response.

    The rest of the time the mirrors were pretty similar.

    On galaxies, the higher strehl mirror gave just enough contrast to pass a threshold where the eye could suddenly detect a dust lane.   The mass market mirror couldn’t reach that threshold.

    Max T, from an online thread entitled, Premium 1/10PV 8″ Newtonian vs mass market 8″ Newtonian.

     

    An inspiring 6″ f/8 ATM build by Matthew Paul, Orange County, New York, USA

    Though I did not  build the scope for imaging, I wanted to share what it is capable of under not so ideal conditions. Very happy with the results of the optics. I need to build a better OTA for it. It’s rather flimsy, the spider is not rigid, the tube flexes, and the focuser is just a plastic rack and pinion, but it works very well for now, and the hard part (the optics) are done. Thank you again to everyone that offered information and assistance as I worked on the mirror.

    MVI_0140-3.jpg

    Matthew Paul(Orange County, New York, USA) quoted here

    Matthew Paul, on 22 Jul 2019 – 3:32 PM, said:

    Though I did not  build the scope for imaging, I wanted to share what it is capable of under not so ideal conditions. Very happy with the results of the optics. I need to build a better OTA for it. It’s rather flimsy, the spider is not rigid, the tube flexes, and the focuser is just a plastic rack and pinion, but it works very well for now, and the hard part (the optics) are done. Thank you again to everyone that offered information and assistance as I worked on the mirror.

    attachicon.gif MVI_0140-3.jpg

    That image ought to give apo owners pause.

    Ed Turco(Lincoln, Rhode Island, USA), from the same thread

    There is real poetic justice in how well a good Newtonian telescope performs.

    JamesMStephens(Hattiesburg, Mississippi, USA), from the same thread.

     

    Hello Marty, I can’t answer all your questions, but I did a shoot out between a 150mm f/8 achor and 200mm f/6 dob on Mars a few years ago at opposition.

    The Dob was much better, I suspect it had more to do with no CA vs the increase in aperture. Mars was smeared with false color rendering very little detail in the views. I sold the Achro because it was too much for me to mount. And in my light polluted sky, I don’t do much low power deep sky.

    I suspect that It would also lose fine detail on Jupiter, but I could not do a side by side compare.

    I have a 6 inch 150 f/5 newt, and it does a good job on Juipter/Saturn. I have not had a shoot out between it and say a 100mm ED, or 120 8.3 acrho for a comparison. As far as personal tastes, my eyes are getting old and are light starved, so usually a brighter less crisp image is preferred over a dimmer crisper one.

    I suspect …. the best scope for viewing the planets at 150mm without going crazy expensive would be the 150 f/8 dob. I’m looking for one right now in the used market. A 120 ed I suspect would do a good job too, but at 4x the price, and a big mount to boot.

    I have an f/5 250 reflector on a dob mount. Best view of Jupiter I have. It does take an hour to cool.

    Vtornado( Northern Illinois, USA), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    I’ve tried them all over the past 40 years.  Best view of planets was through Newts with good mirrors that were properly collimated. Note the underline, because that (particularly the latter) can be an issue with Newts. For something more compact and lightweight a good 6″ Mak is an excellent planetary scope and it won’t cost you an arm and leg.  I just picked up a used Orion 150 Mak and the (visual) images of Jupiter and Saturn are superb. My old 127 Mak is also good but the 150 gives more edge on brightness.

    fcathell(Tucson, Arizona, USA), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    I think a 6” f/8 dob, with top notch optics

    (Spooner) would be a great choice and affordable.

    NHRob, from an online thread entitled: 150mm Instrument for Planets, Which Type?

    6″ mak

    6″ f/8 newt

    4″ fpl-53 double Vixen or triple

    will all give great planet views.

    tomjones, from an online thread entitled: 150mm Instrument for Planets, Which Type?

    tomjones, on 23 Aug 2019 – 01:02 AM, said:

    6″ mak

    6″ f/8 newt

    4″ fpl-53 double Vixen or triple

    will all give great planet views.

    Why add a 4″ into this discussion when it’s an inferior option?  A good 6″ f8 outdoes it.

    azure1961p, from an online thread entitled: 150mm Instrument for Planets, Which Type?

    MalVeauX, on 23 Aug 2019 – 6:33 PM, said:

    So… to add more to this mix…

     

    What would any experienced observers rate a 200mm F6 Quartz reflector to a 150mm F8 ED doublet for planetary views?

     

    Would the extra aperture make enough of a difference?
    Or would the 150mm F8 ED refractor still throw up the better, higher contrast image?

     

    Very best,

    The extra aperture would make enough of a difference if the mirror were superb, the tube material, thermal issues, focuser etc., were all finely tuned and working together. Then there are the ergonomics of viewing position and the question of what type of mount will be used.

    If one were to buy a used 8″ f/6 “classic” EQ mounted Newtonian from a good source, such as someone here on CN, then that would be a very efficient bang for the buck. Especially if the mirror were a known and proven winner. Probably in the Approximately $500 range vs. $2000 for the 150mm f/8 ED.

    “Would the 150mm F8 ED refractor still throw up the better, higher contrast image?” Yes it could, if the 8″ f/6 newt had degraded mirror coating and dust, not collimated perfectly, focuser not smooth, set up on warm surface so that thermals enter the tube and plague the system etc., But in my opinion the Newtonian will win if the details are all taken care of and watched. 

    I wish I could find a local old classic 8″ F/6 EQ mounted Newt to play around with, actually…

    Everlasting Sky( Vancouver, Canada), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    I concur with fcathell, as far as planetary observing with Newtonians when all the necessary conditions are in play. My very best planetary views have been through large truss-tube Dobsonians with premium mirrors, along with large classical Cassegrains, when the seeing has been excellent.

    I also agree with Richard Whalen’s post when the aperture is limited to 6 inches.

    Dave Mitsky(PA, USA), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    Quote

    Even with spot on collimation (Newts, DOBs, Maks, SCT’s, etc.) – you still have a central obstruction vs. none in a refractor and that reduces contrast and resolution…even if just slightly — it does

    It’s worth keeping in mind that the CO does have a small effect on contrast, not on resolution..

    This does mean that a scope without an obstruction, when compared to an other equivalent scope of equal aperture will have reduced fine scale contrast.

    But that’s only if the apertures are identical and the optical quality similar. Otherwise, the contrast is affected by the aperture far more than by a central obstruction. This is why large scopes with COs can provide much greater contrast than a scope without a CO.

    Some years ago I experimented with my 120 Eon by adding a 40% CO, I could see a loss of contrast but it was surprisingly small.

    In this comparison, unless one went with a high quality Newtonians (Spooner) then a $2500 ED Doublet would likely provide better planetary views.

    On the other hand, if weight and length were the guidelines, the a good 8 inch Newt would be hard to beat.

    Jon Isaac( San Diego, California, USA), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    M11Mike, on 24 Aug 2019 – 01:12 AM, said:

    Jon – normally I’m with you 99.9%.  But I have seen numerous times FIRST HAND where a quality 4″ refractor beat out much larger apertures on the planets.  And I don’t think the guys with these scopes didn’t have them properly collimated, etc.  These guys with scopes (like the Meade 10″ SCT) were my observing buddies and they concurred.   They were active seasoned observers like myself.

     

    Mike

     

    Well.. maybe. But you can’t blame that on the CO.  Thermal issues, optical issues, poor seeing..

    Try adding a 35% CO to a 4 inch Refractor and see how much difference it makes.

    Jon Isaac( San Diego, California, USA), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    I’ve had a 6″ F8 newt with 1/8 wave optics and it was excellent for L&P. I’ve got a IM715D mak and the same can be said of it. Big advantage to the mak is in 8 years I’ve never had to collimate it. Either scope would work on my Twilight 2 without a counterweight, I doubt the same could be said of a 6″ refractor. I’ve got an excellent WO ZS110 triplet and it doesn’t outperform my mak or C9.25XLT for L&P unless seeings sub par.

    dscarpa(San Diego, California, USA), from an online thread entitled: 150mm Instrument for Planets, Which Type?

    First Light Report
    Finally, the time had come for first light.  When I put the Glatter laser collimator into the focuser and turned it on to begin aligning the optics, I was stunned to see that the laser beam was hitting the primary mirror inside the circle in the middle of the hotspot.  Despite being driven over 1000 miles and loaded/unloaded twice, the tolerances are tight enough on the telescope. I’ve setup the telescope four different times since – and the initial laser position on the mirror has been inside the 1/4″ (6 mm) hole at the center of the HotSpot every time.  Collimation required less than 1/16 of revolution of any of the knobs on either the secondary or primary mirrors.  I pointed the telescope at the horizon and the zenith.  I moved quickly in altitude and azimuth, and slid the EQ platform through it’s entire range of motion twice.  Collimation didn’t shift.  At all.  
     
    Once the sun dove behind the hills just to the west of the observing site, I uncovered the optics and started the fan in earnest to get the optics cooled to ambient as quickly as possible.  I carry a 10″ rechargeable fan that I used to push air at the front side of the primary mirror, and allowed the built in fan to pull air across the back.  The mirror box is only about 8″ deep in total, so air is able to flow easily around the optics and through the structure to help with temperature changes and cooling. Once full darkness had descended up on the observing site, I removed the front fan, rechecked collimation and got to the business of deep sky observing with the new telescope.  I left the rear fan running at full speed, where it’s just audible as a background noise.  Later I turned this down some just to quiet the fan in the silent nighttime desert. Temperatures dropped 23º F (12º C) over the next 2 hours. The thin optics and open structure of the observing rig did a wonderful job of keeping up with the change.  
     
    When I first began talking with Mike Lockwood about commissioning a fast, thin mirror he told me that I’d likely never seen what a cooled telescope could really do being that my main observing machine has been a 15″ full thickness OMI mirror in a wooden Obsession structure.  I love that telescope, but I learned on this weekend what Mike was talking about.  Conditions that had been blamed for years on poor seeing were not present on this night, even though we all agreed that the seeing wasn’t any better or worse than a typical night at this location.  I spent nearly all of my time over the next few nights observing comfortably with much higher magnifications than I’d ever been able to use previously. 
     
    NGC 5139 – Even though it culminates at just 11º above our southern horizon, Omega Centauri was on the meridian at the end of astronomical twilight, so the three of us agreed that it was the obvious choice for the first target.  We’re all familiar with the views of this object from this site with instruments of all sizes from a 63mm Zeiss refractor to a 20″ f/5 Obsession.  At this low elevation there were some obvious atmospheric artifacts being induced in the image – but we all agreed that this was the finest view we’d had of this granddaddy of globulars.  With a 21mm Ethos I immediately noticed a couple of things.  1 – The telescope maintained perfect balance though it was pointed 10º above the horizon.  When I removed the eyepiece to switch to a lighter one, the telescope didn’t budge.  I’m no designer, but I attribute this to the use of the 30″ altitude bearings and perfectly balanced design.  2 – I was looking at Omega Centauri with 20″ of aperture and a 1.2º true field of view.  The cluster was lost in the middle of a field with all kinds of black space around it. With all that aperture focusing all that globular into the smaller image scale of this wide field, the cluster was astonishingly bright, even by it’s elevated standards.  I hadn’t changed eyepieces or objects yet, and I already knew…..this was going to be a fun telescope.  At 175x in a 10mm Ethos, the cluster is huge, extending nearly to the edges of the field.  What I noticed most was the stars being impossibly tight pinpoints, with black space around them.  The contrast between the globular’s stars and the background sky is the most notable thing from the observation.  
     
    NGC 5128 – This beauty in Centaurus is so close by that you can’t *not* look at it.  Again, the contrast was the most noticeable thing about the observation.  With the 10mm Ethos, the dust lane is sharp and well defined across the face of the galaxy and appears nearly bi-sected with a brighter middle – like looking at the great rift from millions of light years away.  
     
    I wiled away a few hours working through the Virgo cluster high in the west, spent some time counting galaxies in the Coma cluster and then happened upon what has been the most memorable view through this telescope yet.  
     
    M83 – Again, it was the contrast.  An absolute pinpoint of a nucleus with two sharply defined bars extending away for a few arc minutes and then turning sharply to form those beautiful, elegant spiral arms.  What struck me most though was the dark lanes between the arms.  As I continued observing, differences in darkness began to appear in the dark lanes, as well as brighter spots in the spiral arms (HII, OB assocations?).  I didn’t concern myself too much, I just enjoyed the view.  This telescope rocketed this galaxy to a high place on my favorite objects list.  
     
    M57 – I put the telescope on this old standby and basically went camping at the eyepiece.  With an 8mm Ethos, the central star was just there.  It didn’t jump out at you….but it was there and required no effort beyond basic averted vision to see it clearly.  I noted galaxy IC 1296 nearby and that it too was pretty easily seen.  This was where I pushed the magnification.  With a 3.7mm Ethos, the telescope is operating at 475x magnification.  In moments where the seeing settled and the air was steady, the optics weren’t even breaking a sweat.  I was able to observe 4 stars seemingly involved with the nebulosity and the central star was a direct vision object at this magnification.  The interior surfaces of the nebula were clearly mottled and uneven and the entire nebula appeard electric green in the eyepiece.  
     
    Veil Nebula – Always a favorite, our small group spent a solid hour cruising the wisps of this supernova remnant with the telescope.  With an 8mm Ethos and an O-III filter, the nebulosity glows as if backlit by some artificial LED source in the eyepiece.  I traced the entire outline of the nebula noting how the brighter wisps faded into thinner and fainter ones as I followed until they just seemed to disappear.  There’s a patchwork background of nebulosity that I hadn’t noticed before with my 15″ scope.  

    48370580567_bd2a867e80_c.jpg
    Great friend and fellow observer Alan Strauss told me I needed to remain still while observing M101.  Uhhhhh….okay!  That won’t be hard.  I could sit here all night.  
     
    …and then came the planets.  I have listened to Mike Lockwood bang the drum about planetary observing with big aperture mirrors for quite awhile now.  Like I told him afterward, consider me one of the converted.  Jupiter at any magnification was an absolute razor blade of sharpness.  Where I was used to seeing equatorial bands, I was now greeted with a swirling mess of sharply defined festoons and bands within bands.  Viewing Jupiter this night was the best views I’ve had that I can ever remember.  My friend Alan commented a few weeks later that the thing that stood out most to him was how sharp the planetary views were through this 20″ scope – he wasn’t expecting it to perform the way that it did.  I concur.  
     
    Just a couple of weeks ago, I set the telescope up again in my light polluted Phoenix backyard to give a quick view of the moon and Jupiter to my lady.  I’ve not been much of a lunar observer since I was a kid, but she is in love with the moon….so, it was time to show her the moon through the new telescope.  She’s not an astronomer by any means….and she’ll be the first to tell you that she doesn’t have those aspirations.  I was stupefied when I looked in the eyepiece.  Stop me if you’ve heard this before – the contrast is unbelievable  – and not just the inky blackness of the crater shadows and brightness of sunlit portions of the lunar surface.  The subtle variations in illumination in the mare and even light differences in color were obvious and a pleasure to behold.  What was supposed to be a quick 20 minute show of the moon and Jupiter turned in to a 2.5 hour session together.  We spent the longest time comparing notes and pointing out features and seeing the smallest details.  The experience has converted me into someone who’s ready to look at the moon again.  I look forward to the intersection of my travel schedule with a break in the Arizona monsoon and a favorable location of the moon so I can repeat the experience.  
     
    Conclusion
    I wanted big aperture with no ladder and absolutely no compromises on the optical and structural quality of the telescope.  It came with an uncompromising price tag too – but I couldn’t be happier with the combination of the Lockwood optics and Osypowski structure & platform.  Mike Lockwood’s reputation for ridiculously fast, sharp optics is well deserved and I’d even dare say still underappreciated.  I selected Mike as my optician for a couple of reasons.  1 – He was great to talk too and has been a great resource for all astronomy/telescope related questions since first talking with him back in December 2017.  2 – A couple of extremely experienced observers that I respect greatly both said the same thing – that the best view that they’d ever had through a telescope had Lockwood optics.  I can now say I wholeheartedly agree with their assessment. 
     
    The Spica Eyes structure built by Tom Osypowski is as nearly perfect as I think it’s possible to build at this point.  It is substantial, stiff and rigid.  It feels like it’s been built for the apocalypse when you put your hands on it.  I chose Tom because of my experience with his EQ platforms and the knowledge that he’s built several telescopes that were both larger *and* faster than this project – so I was confident i would get a telescope that matched my excitement for the EQ platform.  I haven’t been disappointed.  Twice now I’ve done business with Tom.  Both transactions rank as the smoothest, most pleasant money I’ve spent in this pursuit in my lifetime.  I’m proud to be able to say I own one of his telescopes.  
     
    Is the telescope truly perfect?  No.  I have two minor quibbles.

    • There is some stiction in the azimuth axis.  It’s not paralyzing, but it is there.  I got after it when I got back home with some car wax and a buffing cloth which has improved it.  Part of this issue is comparing it to the buttery smooth goodness that is the motion of an Obsession.  I’ve been spoiled by 18 years of use with my 15″ Classic.  
    • The light shroud fits really, really tight.  Getting it pulled down over the structure is a bit of a process.  By process, I mean it takes a couple of minutes.  Once it’s in place – it stays in place and does a wonderful job of blocking stray light but still allowing airflow through it.  So I’ll count my blessings that these are my issues with the telescope.

    I realize it’s been long winded, but there’s little information out there about Spica Eyes scopes.  In fact, there’s really not much beyond a different CN thread that was posted a few years ago about a 24″ scope Tom built.  I submit this review and future experiences and observing reports as part of that body of knowledge.  Tom Osypowski tends to fly under the radar when discussing premium telescope builders, but his handiwork is among the absolute best out there.  He and Mike Lockwood have earned every bit of credit that they get for their skills and contributions to our hobby. 
     
    Mike

    48260256751_f91f413582_c.jpg
    A great shot of the observing site in Portal, Arizona, the 20″ f/3 telescope described here, and the truck/camper that gives me shelter whilst far from civilization for long periods of time.  The light domes are greatly exaggerated in this long exposure.  The one just to the left of the truck is from Lordsburg, NM – 40 miles (64 km) away.  The light dome to the right is from El Paso, TX – 160 miles (255 km) away.

    Mike Wiles( Phoenix, Arizona, USA), from an online thread entitled, First Light Report: 20″ f/3 Spica Eyes/Lockwood Dobsonian

     

    Recently picked up a used (mint condition) Skywatcher 130mm f/5 PDS reflector OTA (Thanks Tyson). This scope is presently discontinued.

    Cosmetics: beautiful black with silver speckles. 9/10

    Inclusions: 8/10 (based on the nice focuser)

    excellent dual rate 2” Crayford focuser with 1.25” adapter

    Vixen style finder mounting shoe

    thin 4 vein spider/ adjustable 2° mirror holder

    oversized 2° mirror (this scope is designed for photography)

    Enhanced 95% coatings on 1° and 2° mirrors

    6×30 straight through finder (mine was upgraded to an Orion 8×40 straight through version)

    2” 28mm LET eyepiece (not included in my used purchase)

    Nice dual hinged mounting rings and Vixen style mounting 7” bar

    Peeves:

    Crayford focuser is non-compression ring

    Crayford focuser has a thread 2” adapter ring using a single metal set screw

    (I removed the ring and drilled/tapped 3 holes a 120° and replaced the metal set screw with 3 nylon ones). I actually prefer this type with nylon screws to a compression ring version.

    the 2”-1.25” eyepiece adapter is also thread-on. You need to unthread the 2” eyepiece adapter ring and the thread the 2”-1.25” one on. Stupid design, just include a regular 2”-1.25” – compression ring or set screw.

    You need a 2” extension tube to reach focus with either 2” or 1.25”, It is not included.

    The included 28mm 2” LET eyepiece is junk (I have tried one). Just include a 1.25” cheapo 25mm Plossl eyepiece.

    I hate straight through finder scopes, replaced mine with an Orion 6×30 RACI version (very light weight but a larger 50mm RACI maybe a better option.

    Optics: 10/10

    easily collimation (it arrived in perfect collimation), 1° mirror is center spotted

    3 spring loaded adjustment knobs with setscrew locks

    95% enhanced 1°/2° mirrors – brighter view than my larger 140mm f/3.64 Comet Catcher

    optical testing – easily 1/8 wave or better

    Observing: I am mainly a Deepsky observer – this a definite RFT

    Fantastic scope, easily punches above a 5” reflector.

    easily takes 160X + (TV 4mm DeLite) , 40x/in- you run out of light grasp

    From low power wide field (3° +) to high power, does it all.

    with high quality eyepieces, I did not need an OCS (Paracorr)

    Some Deep Sky highlights: NELM 5.7 Transparency/Seeing Both 3/5 :

    the Double Cluster – superb, one of my best views ever (mono view)

    NGC 7789 in Cassiopeia (Caroline’s Haystack) – very easy (large smudge with a sprinkling of brighter stars)

    M31 group – all 3 members are easy with direct vision – M31 over 2.25°, M110 diffuse oval

    M33 – large 3/4° smudge

    M81/82 – beautiful contrast in galaxy types

    M51 – Both parts easily visible

    M13 – easily resolved – perfect image (pin **** stars) at 160x

    M27 – amazing with and without filters

    NGC 7000 – fantastic North American shape with NPB filter

    Veil Complex – see my posting in Observing section (Veil in small scopes)

    Future Upgrades:

    I have added a 8” dew-shield

    I will flock the OTA (either the entire tube or opposite the focuser)

    Summary:

    An excellent low priced RFT. Amazing Optics.

    The few minor “peeves” are easily corrected.

    Highly Recommended !!

    vkhastro1(Ontario, Canada), from an online thread entitled, Skywatcher 130f/5PDS-mini review

    Congrats on your new scope! 

    My experience mirrors yours. It is kind of an “unknown” scope, but for my own application it is working better than the Comet Catcher in spite of being smaller and “slower.”

    This scope is kind on the stealth list because when I say I have a 130mm f/5, everyone thinks it is a typical 130mm with small illuminated field and 1.25″ focuser and most do not seem to be aware of the 130 PDS.

    vkhastro1, on 30 Aug 2019 – 5:19 PM, said:

     

    95% enhanced 1°/2° mirrors – brighter view than my larger 140mm f/3.64 Comet Catcher

    optical testing – easily 1/8 wave or better

     

    These are factors that I used in my decision to move from the Comet Catcher to the 130 PDS.  Now my situation was that I am using image intensified eyepieces and I came to feel that the Comet Catcher was punching well below the f/3.6 spec.

    Some of this I thought was maybe due to the need to re-coat the mirrors, but after a painful testing sequence, I determined that the mirrors were OK, but that they were just not transmitting a lot at longer wavelengths (which is important for NV use) and this combined with the losses of the secondary shading and the corrector (which is where perhaps 10% of the loss in near infra red is coming from) meant that the scope simply was not as bright as I thought is should be. I actually think that the entire system transmission (including secondary shading) of the Comet Catcher really does cause it to loose a lot of brightness. I came to feel that the CC was simply much dimmer than it should be for a 140mm f/3.6 scope.

    The other issue I had with the Comet Catcher was the sled focuser and the awkward nature of trying to get it to work with a filter wheel.  The 130 PDS though, with its 2″ focuser with plenty of travel made it easy to use a filter wheel.

    One important point though is that while it is an “Imaging” scope, I don’t think it will fully illuminate an APS-C size sensor.  My NV monocular has an 18mm image circle, and I can see that there is a little illumination falloff at the edge.  Not bad, but it does not appear to have a fully illuminated circle bigger than maybe 12mm. Probably good for an APS-C with some cropping maybe or a 4/3.

    Anyway, as much as I loved the light weight and simplicity of the Comet Catcher, I came to feel that it was much dimmer than the numbers suggested and moved to the 130 PDS and like you, I really feel that it is brighter than the Comet Catcher was. 

    Nice scope.   Not many around as far as I can tell though.  

    130PDS R.jpg

    (Also, the image scale was a plus.  An added bonus was that I had enough focuser travel to use the Barlow lens mounted in one of my filter wheel positions.  This Barlow gives me the ability to bump up the power by about 1.5x just by turning the filter wheel and refocusing.  That is a nice benefit.)

    Good review of what appears to be a relatively unknowns scope.  Hope you are enjoying it!

    Eddgie, from an online thread entitled, Skywatcher 130f/5PDS-mini review

    Very informative comments. I picked up one of these a few weeks ago and use it on a Skywatcher Star Discovery Go To mount that I already had. Quick to set up and cool down, great optics and works really well with my Vixen LVW eyepieces. Nothing to dislike at all.

    brisdob(Brisbane, Australia), from an online thread entitled, Skywatcher 130f/5PDS-mini review

    We are looking into this model and it’s larger models currently.

    Skyward Eyes( Skywatcher USA Vendor), from an online thread entitled, Skywatcher 130f/5PDS-mini review

    For a number of years I had a SpaceProbe 130 ST fitted with a 2 inch Focuser. I normally used it with a Paracorr.. A Paracorr would address the need for an extension tube.

    I have said this before.. a good 130 mm F/5 Newtonian is the closest thing an affordable 4 inch apo Refractor that exists… The 130ST was quite good on planets and doubles as long as it had an hour or so to cool.

    I remember one dark night.. I swapped out my TeleVue NP-101 for the 130 mm F/5  with the Paracorr and 31 mm Nagler..it was scary how good it was.. 

    4920795-SpaceProbe 130ST Starpad.jpg

    Jon Isaac(San Diego, California, USA), from an online thread entitled, Skywatcher 130f/5PDS-mini review

    Ya don’t say; I got me one of them there ‘scopes….ken. I’ve no’ got the 2″ focuser mind, but I dinnae really need it. My bestest grab ‘n’ go ‘scope ever. Eye.

    Mr. Hardglass

    I’m a massive fan of 130 f5’s, even on the ota’s that are limited to 1.25″ ep’s. Very easy to mount scopes, and, when they have decent optics, great all around performers.

    Kerry R.( Mid-west Coast, Michigan, USA), from an online thread entitled, Skywatcher 130f/5PDS-mini review

    I have been using this telescope for around 6 months now on my evolution mount as an eaa platform. For the cost, it makes an excellent alternative to my 925 for wider field views and it can reach zenith with no problems.

    Barkingsteve, from an online thread entitled, Skywatcher 130f/5PDS-mini review

    ***

    FINALLY a Dob I really enjoy.

    Been through many different sizes, ranging up to 16 inches.  For me, a 12.5″ Dob is in the goldilocks zone.  Big enough to astound me with the views, but small enough to use every clear night.

    I can’t get enough.  In just 11 weeks of ownership, I’ve used it 42 times, including several trips to dark skies (3.5 hours each way).

    Ryan built a masterpiece.  It’s wonderfully engineered & built.  The telescope is so easy to assemble & disassemble. 

    In use, it is sheer joy.  The movements are silky smooth, requiring little pressure to track an object even at 300x.

    And the views?  Just mind-blowing.  Never thought a reflector could be so sharp and have such stark contrast.  This is the first time I’ve looked through a Zambuto mirror, and the views are as close to a refractor as I’ve ever seen in a mirrored telescope.

    During the last new moon, at extremely dark skies, I pulled the old M13/NGC6207 trick on an observer.  I got her to focus on NGC6207 at 250x.  After several minutes, I asked her to nudge the scope downwards slowly.  A gasp soon followed.  Then the hooting & hollering.  I understood her enthusiasm.  M13 looked photographic.

    Ryan was very gracious throughout the build process.  He promptly & politely answered all my emails, and was very patient, despite my impatience.  He is a master of his craft, and actually converted me from a refractor guy, to someone who can enjoy the night-sky using both types of telescopes.

    Attached Thumbnails

    • CN (2).JPG

    Magnitude 7, from a thread entitled, New Moon Telescope 12.5″ Zambuto refract… er… reflector.

     

    Aperture. Obviously of a decent quality, but aperture is what reveals detail.

    Small telescopes deliver a low magnification sharp looking view, but the fine detail doesnt exist. Its sharp because the magnification is low.

    Double the aperture, double the resolution, simple as that, provided the atmosphere obliges! Which it does more often than some people would maintain.

    Happy Limpet(Southampton, UK), from an online thread entitled, What’s more important.

    If you’re going to use a reflector, mirror quality is very important. I learned this when I had my 2001ish vintage Nova mirror refigured by Mike Lockwood this year. One of the biggest differences I noted was the moon. Before, I could see features on the moon, but the smaller ones could not really be seen, or made sense of, when examined closely. It’s a hard thing to describe, but it was something I noted often, and found frustrating. Detail in the refigured mirror is much clearer in this respect, probably more refractor-like.

    If refractors give a more tightly-controlled image than a similar-quality reflector, then that would be the way to go for lunar.

    I wonder how much the resolution advantage of a large aperture reflector is lost due to diffraction, coma, viewing through a wider expanse of air and a filter, compared to a more modestly sized apo. Maybe you really need to compare apos to apos.

    Mike Tahitub, from an online thread entitled, What’s more important.

    posted 09 October 2019 – 08:16 AM

    MikeTahtib, on 09 Oct 2019 – 10:26 AM, said:

    I wonder how much the resolution advantage of a large aperture reflector is lost due to diffraction, coma, viewing through a wider expanse of air and a filter, compared to a more modestly sized apo.  Maybe you really need to compare apos to apos .

    Diffraction – essentially none.

    Coma – none if using a coma corrector, very little otherwise (depending on f ratio)

    Viewing through a wide expanse of air – none, assuming you know how to get to thermal equilibrium (clue – use fans, its easy)

    A filter? none also

    How much extra money stays in your pocket? Vast.

    Reflectors rule.

    Happy Limpet(Southampton, UK), from an online thread entitled, What’s more important.

    Jon, my experience has been thus – with my Celestron Omni 102mm f/10 (now retired), the moon looked very good, detail was good, contrast as good as could be expected for an achromatic scope, CA was well controlled, but still present. With my SW 120 ED, more detail stood out, I was beginning to see an almost 3D view of things, especially along the terminator. I could also bring the magnification up a bit more than the 102mm, but the seeing conditions had more impact. And CA? What CA?

    With my 10 inch reflector, it is an OMG experience… I had it out Monday night and it quickly reminded me why I love this scope. The detail and contrast that is visible is like being in a Lunar lander on approach… words simply can’t describe the view. The 3D appearance was eye popping. It was a decent night, not great, with the seeing like a 3/5, so at higher mags, there was a bit of waviness at times, but mostly good. Keep in mind that my 10 inch reflector is an ATM scope, so a lot of attention was put into getting top performance.

    This has just served to remind me that a good refractor is no slouch… but has some limitations. A good reflector with some aperture is magical.

    Good hunting!

    Seabee 1, from an online thread entitled, What’s more important.

    My favorite scope for lunar visual is my 8″ f/9. When seeing is good the view is tack sharp. The best view ever was with my 25″ on a extremely steady night. I was hitting 1000x and still had a sharp image.

    Like Jon, no filter.

    Keith Rivich(Cypress, Texas), from an online thread entitled, What’s more important.

     

    More on Double Stars with a  commercial 8″ f/6 Newtonian

    This report is the fifth installment of a series of observational investigations I have made using an 8 inch f/5.9 reflecting telescope.

     

    Check out this link for goals and methods used in this study:

    https://www.cloudyni…-and-monoceros/

    Corona Borealis
    COU 610 Theta (15329+3122) mags 4.27/6.29; pa = 199°; sep = 0.85“, (orbital estimate for 2019.3 is a better fit with historical 4th Int. Cat. data vs last precise from 2016)
    345x, 460x:  single star
    627x:  brightening of diffraction ring that resolves to small dot that is just split 20% of time; at resolution limit and very challenging; re-measure of separation desired

    Draco
    HU 149 (15246+5413) mags 7.48/7.62; pa = 270°; sep = 0.665“, (2016, last precise; solid data)
    345x:  moves past elongated to notched (snowman) 30% of time
    460x:  at resolved/split border as seeing allows; both stars are light yellow-orange
    627x:  resolution aided with orange filter under excellent seeing conditions; a bit above resolution limit

    Image below is from 2017.444

    STF 2054AB (16238+6142) mags 6.15/7.09; pa = 351°; sep = 0.943“, (2017, last precise; solid data)
    345x:  easily seen as split 100% of time to two white stars of slightly dissimilar magnitude; above resolution limit
    image below is from 2019.455

     

    STF 2218 (17403+6341) mags 7.08/8.37; pa = 308°; sep = 1.476“, (2015.5, Gaia DR2; solid data)
    345x:  split 100% of time to two whitish stars; averted vision aids visualization of the fainter secondary; above limit

    STF 2403 (18443+6103) mags 6.25/8.35; pa = 278°; sep = 1.061“,  (last precise, 2011; solid data)
    345x:  seen as just split 50% of the time; both stars are yellow with the much smaller secondary sitting a bit past the first diffraction ring; above resolution limit
    There may be a number of observations for this one as it is part of the Sissy Haas Uneven Double Project

    STT 369 (19071+7204) mags 7.82/7.91; pa = 8°; sep = 0.684“, (2015.5, Gaia DR2; solid data)
    345x:  just split when seeing allows; both stars are yellowish-orange with secondary a bit smaller
    460x:  easier to see as split; above resolution limit

    MLR 12 (18293+8235) mags 8.90/9.12; pa = 222°; sep = 0.689“, (2008, last precise; data is old)
    345x/averted vision:  mostly pointy
    460x/averted vision:  much smaller secondary seen as resolved only 20% of the time—very difficult; right at resolution limit; separation re-measure needed

    STT 312AB Eta (16240+6131) mags 2.80/8.20; pa = 143°; sep = 4.676“,  (2015.5, Gaia DR2; solid data)
    345x:  secondary is a tiny speck of light well separated from the primary; held steadily in view on nights of better seeing; above resolution limit

    Hercules
    COU 107 (16169+1948) mags 9.02/9.61; pa = 113°; sep = 0.609“, (2009, speckle; data is old, scant)
    345x:  very faint; merely a bit elongated; below resolution limit; important data point to assess faintness factor; re-measure of separation needed

    STF 2107AB (16518+2840) mags 6.90/8.50; pa = 107°; sep = 1.443“,  (2015.5, Gaia DR2; solid data)
    345x:  easily split; both stars are whitish and the secondary is quite a bit smaller than the primary (but not tiny); above resolution limit

    A 350 (16540+2906) mags 9.47/9.61; pa = 144°; sep = 0.630“, (2019.542, own measure; considered solid because in line with 4th Int. Cat. trend)
    345x:  possibly pointy (not resolved); faint!
    460x/averted vision:  barely resolved when seeing permits with the secondary appearing just a bit smaller versus the primary; at resolution limit; important data point to set faintness factor

    Image below is from 2019.542

    BU 627A, BC (16492+4559) mags 4.84/8.45; pa = 40°; sep = 2.116“, (orbital estimate for 2019.4; system is opening; value is in line with last precise [2.06”] and Gaia DR2 [2.105”])
    345x:  easily split; both stars are white and secondary is quite small; above resolution limit
    Inverted image shown below is from 2017.501

    BU 812 (16071+1654) mags 9.06/9.36; pa = 96°; sep = 0.73“, (2011, last precise; data may be incongruent with historical 4th Int. Cat. values)
    345x/averted vision:  image moves past elongated to notched about 40% of time showing two similar magnitude, faint stars; a re-measure of both separation and delta mag is desired; considered a bit above resolution limit

    A 228 (17063+2631) mags 9.31/9.88; pa = 13°; sep = 0.658“, (2019.553, own measure; system is opening)
    345x/averted vision:  image is at the elongated/resolved border; discs are tiny—very faint!
    460x/averted vision:  resolved about 50% of the time; a bit above the resolution limit
    Note:  listed magnitudes are from Hipparcos, not Tycho
    Image below is from 2019.533

    HDS 2446 (17177+3717) mags 4.62/8.53; pa = 143°; sep = 0.918“, (2010, last precise; solid data)
    460x:  split ~100% of time on night of very good seeing; adding an orange filter to the optical train causes the secondary to nearly disappear which explains the exceptional difficulty experienced imaging this object; above resolution limit

    STF 2315AB (18250+2724) mags 6.57/7.77; pa = 115°; sep = 0.600“, (orbital estimate for 2019.4; solid data)
    345x:  merely a bit oblong
    460x:  moves past elongated to a snowman shape about 30% of the time—stars clearly of dissimilar magnitude; on border of resolved but never actually seen as resolved; appears to be just below resolution limit
    Inverted image shown below is from 2017.512

    BU 641 (18218+2130) mags 7.03/8.66; pa = 341°; sep = 0.78“, (2015, last precise; solid data)
    345x:  moves past pointy to resolved about 10% of the time; secondary is much smaller
    460x:  seen as split when seeing allows image to sharpen (~30% of time); above resolution limit

    STF 2339AB, CD (18338+1744) mags 7.45/8.67; pa = 277°; sep = 1.482“, (2018, last precise; likely solid data)
    345x:  easily split to show fine magnitude contrast pair with primary seen as white and secondary as light orange; above resolution limit
    460x/averted vision:  secondary [CD] now appears elongated—it has a rho value of 0.492” and is known as WAK 21CD—a very nice bonus!

    A 238 (18114+2519) mags 8.59/9.55; pa = 74°; sep = 0.632“, (2019.548, own measure)
    345x:  persistently pointy
    460x/averted vision:  moves past elongated to resolved 20% of time; secondary is tiny; at resolution limit
    Image shown below is from 2019.548

    A 2093 (18054+1624) mags 9.09/9.85; pa = 226°; sep = 0.642“,  (2008, last precise; data is old but considered solid)
    460x:  very faint, elongated rod that presents as resolved perhaps 5% of the time; at or slightly below resolution limit

    TDT 1042 (18461+1328) mags 8.85/9.65; pa = 274°; sep = 0.7“,  (2009, last precise; data is old, not solid)
    345x:  merely point; stars are faint
    460x:  sharpens to resolved from a rod shape about 10% of time; at resolution limit; re-measure of separation needed

    STF 2084 Zeta (16413+3136) mags 2.95/5.40; pa = 112°; sep = 1.373“,  (grade 1 orbital estimate for 2019.211)
    345x:  light orange secondary just touching bright white primary—beautiful!  Above resolution limit
    Image shown below is from 2019.452

    STF 2203 (17412+4139) mags 7.72/7.81; pa = 293°; sep = 0.757“, (2015.5, Gaia DR2; solid data)
    345x:  just split to two white stars—not difficult; above resolution limit

    Libra
    STF 3090AB (15087-0059) mags 9.09/9.34; pa = 287°; sep = 0.627“, (2017, last precise; little corroboration from 4th Int Cat.)
    460x:  elongated only; never resolved
    627x/averted vision:  never moved past elongated; below resolution limit; not sure why this object is so difficult—a re-measure of separation is desired

    I1269AB (15249-2322) mags 8.73/8.84; pa = 199°; sep = 0.654“, (2015.5, Gaia DR2; solid data)
    345x/averted vision (best conditions):  resolved to two white stars of very similar magnitude about 30% of the time; at or slightly above resolution limit; important data point to establish minimum rho value for calculator

    BU 225BC (14255-1958) mags 7.16/8.37; pa = 91°; sep = 1.285“, (2015.5, Gaia DR2; solid data)
    345x:  split 100% of time showing the primary as white and the secondary as light yellow and smaller; above resolution limit; a beautiful triple with the AB pair designated SHJ 179 or H N 80

    HJ 4756 (15197-2416) mags 7.90/8.27; pa = 242°; sep = 0.574“, (2015.5, Gaia DR2; solid data)
    345x/averted vision:  moves past elongated to notched 50% of time (never resolved)
    460x:  resolved 50% of time; discs are very small and appear similar in magnitude; a bit above resolution limit; important data point to establish minimum rho value for calculator

    A 81 (15089-0635) mags 9.43/9.76; pa = 41°; sep = 0.68“, (2005, last precise; data is old and scant)
    345x/averted vision:  rod only; stars are very faint
    460x/averted vision:  moves past elongated to resolved at most 5% of the time; below resolution limit; re-measure of separation desired

    Lyra
    HU 1300 (19202+3411) mags 8.92/9.56; pa = 184°; sep = 0.74“, (2015, last precise; data is solid)
    345x/averted vision:  mostly a single star, but possibly rod-shaped; faint!
    460x:  at most rod-shaped (never resolved); below resolution limit which makes this object an outlier—further investigation warranted

    A 703 (19072+4451) mags 9.01/9.28; pa = 189°; sep = 0.57“, (2010, last precise; likely solid data)
    as yet unobserved; important data point to establish faintness factor for resolution calculator

    BU 648AB (18570+3254) mags 5.34/7.96; pa = 243°; sep = 1.303“, (grade 2 orbital estimate for 2019.3)
    460x:  small brightening apart from the primary that sharpens to a small disc that is seen as split 50% of the time
    627x:  split 100% of time; secondary is much smaller, both stars appear white; above resolution limit

    Have you observed or imaged any of these double stars?  I would love to hear of your endeavors with these objects.  Are there other, similarly challenging objects in these constellations that I have missed?  Let me know.

    Nucleophile(Austin, Texas, USA), from an online thread entitled; 8 Inch Reflector Investigations. Part V: Corona Borealis, Draco, Hercules, Libra, and Lyra.

    Hu149_DRA.jpg

    STF 2054AB

     

    STF2054AB_DRA.jpg

    A350_HER.jpg

    STF2315AB_HER.jpg

    STF 2084 Zeta

     

    STF2084_Zeta_HER.jpg

    STF 2084 Zeta

     

    STF2084_Zeta_HER.jpg

    A238_HER.jpg

    Nucleophile(Austin, Texas, USA), from an online thread entitled; 8 Inch Reflector Investigations. Part V: Corona Borealis, Draco, Hercules, Libra, and Lyra.

    Excellent as always Mark!

    Here are some of my observations from your list, plus a few others you might try:

    Cou 610 AB: 8″ 667x: Notched/snowman at best moments.  B definitely fainter and almost blue.  Very faintly split, looks like a blue appendage.  20″ diffraction is too messy.

    STF 2107 AB: !! 12.5” This was a CDSA plot find, didn’t expect it to be special.  Yellow and orange pair, very close ~1.5″, 1 delta mag.  Very pretty.

    STF 2315 AB: 12.5” 553x.  Near contact / overlapping disks, 0.5 delta mag.

    BU 641 AB: 12.5” 553x. !! Extraordinary!  Moderately bright A and much fainter B, <1″ separation.  Seeing needs to still.

    STF 2339 AB-CD: 20”: 533x: White and dull white B. Close but well separated, ~1″ [AB-CD seen. AB is Hu 322 1 delta mag 0.2″, not noticed]

    STF 3090 AB: 12.5” Notched to hairline split at the best moments. Faint pair, tough. Seeing not good enough to go above 553x. [AB seen; AC fainter and wider.]

    BU 648: 8″ 333x: 3 delta mag, at first diffraction, needed critical focus and seeing.

    OTHERS:

    Met 9: 8″ 205x nothing.  8″ 410x suspect elongation.  667x see a fleeting, bluish point just outside of first diffraction ring.  A is light yellow orange and bright; 2 delta mag. to B.  A feels elongated / egg shaped.  At 20″ and 667x the seeing is too messy though there is a knot in the diffraction where I had noticed the point with 8″.  Strong feeling A is elongated.
    12h 54m 39.98s +22° 06′ 28.8″ P.A. 51 sep 1.7 mag 5.70,7.77 Sp F8V+M2-3V dist. 33.85 pc (110.42 l.y.)

    STF 1967 = Gamma CrB: Definite mis-shape, oval to egg.  8″ 667x.
    15h 42m 44.57s +26° 17′ 44.3″ P.A. 104.6 sep 0.22 mag 4.04,5.60 Sp B9V+A3V dist. 44.78 pc (146.07 l.y.)

    STF 2289: Just split in 20″ at 205x, but flaring. 333x had messy diffraction. 8″ mask at 333x gave clean disks, split, ~0.7″. Dull yellow and yellow-red colors.

    18h 10m 08.69s +16° 28′ 35.0″ P.A. 215.3 sep 1.24 mag 6.65,7.21 Sp A0V+G0III dist. 263.85 pc (860.68 l.y.)

    STT 359: !! Kissing 8″ 333x, hairline split 667x. 20″ too diffracted. Near equal white A and bluish white B.
    18h 35m 30.40s +23° 36′ 19.9″ P.A. 3.7 sep 0.75 mag 6.35,6.62 Sp G9III-IV dist. 144.3 pc (470.71 l.y.)

    A 260 AB: 20″ 667x: At 8″, small and faint suspected split at 333x: 8″ 667x stars are hazy. At 20″ 667x got a clean wide split two hard paints of stars.
    18h 57m 34.07s +32° 09′ 20.2″ P.A. 244 sep 0.8 mag 9.17,9.60 Sp A0

    STF 2422: 8″ 333x: Excellent hairline split at 333x with 8” mask. Near equal white stars. Picked them out in a crowded field, suspected elongation right away, split with seeing as I centered it in eyepiece, and from then it was a steady split
    18h 57m 07.83s +26° 05′ 45.1″ P.A. 68 sep 0.8 mag 7.93,8.25 Sp A2IV dist. 156.25 pc (509.69 l.y.)

    AGC 9 AB = Sulafat: 8” 533x: B star immediately picked out of A’s glow like a piece of debris suspended in the explosion, or a planet hanging in the halo.
    18h 58m 56.62s +32° 41′ 22.4″ P.A. 307 sep 13.5 mag 3.24,12.10 Sp B9III dist. 190.11 pc (620.14 l.y.)

    HO 92 AB 20″ 667x: ! Beautifully well split, had an instant of perfect images. White pair near equal.
    19h 00m 59.89s +32° 33′ 11.6″ P.A. 40 sep 1.3 mag 10.59,10.85

    COU 1156 AB 20″ 667x: ! Near qual small and at best moments a clean split, still, just nice points. great star.
    19h 00m 34.25s +33° 01′ 24.8″ P.A. 111 sep 0.7 mag 11.14,11.25

    STF 2461 AB = 17 Lyr: 20″ 667x: ! Huge delta mag. B is obvious in 20″, though A’s diffraction was horrible. Used 8” mask to clean it up but the B star momentarily disappeared, though I could eventually pull it back out with seeing and critical focus. 4 delta mag.
    19h 07m 25.58s +32° 30′ 06.2″ P.A. 281 sep 3.2 mag 5.26,9.10 Sp F0V dist. 41.58 pc (135.63 l.y.)

    mccarthymark(San Francisco, California, USA), from an online thread entitled; 8 Inch Reflector Investigations. Part V: Corona Borealis, Draco, Hercules, Libra, and Lyra.

     

     

    To be continued…………………..

     

    Neil English unearths plenty more historical evidence testifying to the prowess of Newtonian reflectors in his large historical work, Chronicling the Golden Age of Astronomy, newly published by Springer-Nature.

     

    De Fideli.

     

    A Commentary on Two Biblical Paraphrases: ‘The Living Bible’ & ‘The Message.’

    Two popular Biblical Paraphrases; the ‘Living Bible’ & ‘The Message.’

    Therefore, I, the Lord God of Israel, declare that although I promised that your branch of the tribe of Levi could always be my priests, it is ridiculous to think that what you are doing can continue. I will honor only those who honor me, and I will despise those who despise me.

    1 Samuel 2:30 (TLB).

     

    We live in exceptionally enlightening times. Advances in scientific knowledge are now toppling Darwinism as an ideology which underpins much of the world views of secular humanism and has become the dominant ‘religion’ of the west. Influential characters like Richard Dawkins, Sam Harris, Daniel Dennet, Steven Pinker and Jerry Coyne have often quipped that Darwin enabled them to be “intellectually fulfilled atheists.” Now that Darwinism is emerging as an elaborate fraud, or an intolerant secular religion, wouldn’t it be more accurate to describe their plight as ‘scientifically deluded bufoonery?’

    But it cuts deeper still, much deeper. Darwinism has informed large swathes of human knowledge beyond the basic biological sciences, including the ‘soft’ sciences of psychology and sociology, which in turn have inspired a whole raft of ‘mind-body-spirit’ books written by gurus who have taken advantage of a scientifically naieve readership. And, let us not forget that the same “monkey religion” has formed the basis of a panoply of New Age ideas under the broad umbrella of “Cosmic or Psychic Evolution.” What is more, pantheism, which is the foundation of many eastern religions, has also found Darwinism to be a natural bed fellow, not to mention a raft of UFO religions and all the rest of it. Even the scientific quest for the existence of extraterrestrial intelligence – itself a religion in many ways – has failed miserably because of the acceptance of Darwinism among its brethern. Worse still, many Christian denominations have been bullied into accepting Darwinian evolution as a ‘scientific fact,’ and in so doing has forced some Christian and Jewish theologians to formulate the theological mumbo jumbo that is ‘theistic evolution’, where the Creator is reduced to being a bumbling idiot, blissfully unaware and even unable to know what sort of lifeforms would eventually emerge to seek Him out!

    But that is not what a plain reading of Scripture teaches.

    I walked away from Catholicism because of these(and other) sonorous developments, and I’m also aware that many so-called ‘reformed’ Protestant denominations are similarly deceived. Faced with these embarrassing developments, it’s no small wonder that traditional Christianity, that is, Biblically based Christianity,  remains a vibrant, intellectually robust and growing world movement that is now attracting more and more people back into its fold, because of its solid historicity, common-sense wisdom, as well as its strong correlation with objective truth.

    For these reasons, there are compelling motivations to introduce the Biblical allegory to a new generation of people who have ultimately found their ‘pick ‘n’ mix’ spirituality to be, well, ‘ a few sandwiches short of a picnic,’ as the old adage goes, empty or meaningless, who have never heard the true Biblical message, nor properly considered its truth claims. This includes a huge body of so-called ‘nominal Christians’, who apparently believe that morals evolve too.

    Yep, yes siree.

    They’ll happily attend Church on Sunday, vote for abortion on Monday, gay marriage on Tuesday and proudly wave an LGBTQ rainbow flag in your face on Wednesday. Claiming to act in the name of ‘tolerance, peace and love,’ they’ve turned Jesus into ‘Swampy,’ a tree-hugging hippy, which is idolatory, blissfully unaware that what they are actually doing is inviting His wrath.

    That’s what the Bible plainly teaches. Have you not read that God’s morals are unchanging? And just like living things, do you not understand that the statutes of the Living God (one of His Biblical titles) have not evolved either?

    For I am the Lord—I do not change.

    Malachi 3:6 (TLB)

    In a reaction to these worrying global trends, there has been a proliferation of new Bible versions that have popped into existence over the last few decades, which have actively moved away from the terse and often archaic language of yesteryear, and which have gone to great lengths to keep its themes relevant to a 21st century audience, but without twisting its doctrines.

    In this blog, I would like to briefly discuss two such versions; The Living Bible and The Message, both of which were written by Godly men, driven by an over-arching belief that the Judeo-Christian world view is not only true but can transform and enrich human life more than any other holy book or life philosophy.

    The Living Bible(TLB) was first published in 1971 by Kenneth N. Taylor(1917-2005) by Tyndale House Publishers. It is a paraphrase of the Bible, based predominantly on the text of the 1901 American Standard Version (ASV). In his own words, Taylor explained his motivations for making this paraphrase:

    The children were one of the chief inspirations for producing the Living Bible. Our family devotions were tough going because of the difficulty we had understanding the King James Version, which we were then using, or the Revised Standard Version, which we used later. All too often I would ask questions to be sure the children understood, and they would shrug their shoulders—they didn’t know what the passage was talking about. So I would explain it. I would paraphrase it for them and give them the thought. It suddenly occurred to me one afternoon that I should write out the reading for that evening thought by thought, rather than doing it on the spot during our devotional time. So I did, and read the chapter to the family that evening with exciting results—they knew the answers to all the questions I asked!

    Taylor was not a Biblical scholar though, and so did not understand Hebrew or Greek. That being said, he did apparently submit earlier drafts of this work to a team of Biblical scholars prior to its publication. The TLB enjoyed enormous success, especially among the evangelical community, endorsed as it was by Dr. Billy Graha(who distributed copies  to folk during his famous Crusades) and other great Bible teachers of the late 20th century. Indeed, in 1972-3, the TLB was the best-selling title in America! Soon a Catholic version was produced, with an imprimatur by the Pontiff, John Paul II. By the mid-1990s, it is estimated that some 40 million copies had been sold, translated into 100 languages throughout the world. Clearly, there was an appetite for God’s word written simply and effectively for an adoring readership. It also formed the basis of a proper thought-for-thought translation of the Bible, called the New Living Translation(NLT), which I reviewed here. I am reliably informed that the NLT is one of the most popular Bible translations available in the English language today.

    I suspect my own copy of the TLB is much like many other people; a lovely green soft-padded, hardback cover adorned with a Celtic Cross:

    The iconic cover of the hard-backed TLB with its emblematic Celtic Cross.

    The large print edition first appeared in 1979 and my own version was one from the 16th printing of 2014:

    The easy-to-read large print double column layout of the TLB.

    The language is simple and easy to understand, so even a child can assimilate it. Consider the well-loved Psalm 19:

    Psalm 19

    19 The heavens are telling the glory of God; they are a marvelous display of his craftsmanship. Day and night they keep on telling about God. 3-4 Without a sound or word, silent in the skies, their message reaches out to all the world. The sun lives in the heavens where God placed it and moves out across the skies as radiant as a bridegroom[a] going to his wedding,* or as joyous as an athlete looking forward to a race! The sun crosses the heavens from end to end, and nothing can hide from its heat.

    7-8 God’s laws are perfect. They protect us, make us wise, and give us joy and light. God’s laws are pure, eternal, just.[b] 10 They are more desirable than gold. They are sweeter than honey dripping from a honeycomb. 11 For they warn us away from harm and give success to those who obey them.

    12 But how can I ever know what sins are lurking in my heart? Cleanse me from these hidden faults. 13 And keep me from deliberate wrongs; help me to stop doing them. Only then can I be free of guilt and innocent of some great crime.

    14 May my spoken words and unspoken thoughts be pleasing even to you, O Lord my Rock and my Redeemer.

     

    As you can see, the TLB comes with some footnotes and cross-references, just like a regular reference Bible.

    The problem with paraphrases is that they can import the author’s ideas concerning what a tract of Scripture means, which may add or detract from the intended meaning of the original Biblical authors. And that includes gravitating towards particular theological positions. For example, Taylor appears to entertain a pre-millenial point of view, that is, the prophesised millenium of blessedness as outlined in the Book of Revelation will occur immediately after Christ returns to Earth. This is quite clear from certain passages in the TLB. Consider this tract from Isaiah:

    In the last days Jerusalem and the Temple of the Lord will become the world’s greatest attraction,[a] and people from many lands will flow there to worship the Lord.

    Isaiah 2:2 (TLB)

    Comparing this to the NASB, a highly literal version of the Bible, we read:

    Now it will come about that
    In the last days
    The mountain of the house of the Lord
    Will be established [a]as the chief of the mountains,
    And will be raised above the hills;
    And all the nations will stream to it.

    Isaiah 2:2 (NASB).

    Notice how Taylor included “Jerusalem” and “Temple” although these do not appear in the original Hebrew.

    This is all well and good if the reader is entertaining a pre-millenial position but it might prove problematic to those who do not hold, or develop, other views.

    Another issue is that errors creep in which can be a source of confusion to the reader. Consider this passage from the TLB from Romans;

    These things that were written in the Scriptures so long ago are to teach us patience and to encourage us so that we will look forward expectantly to the time when God will conquer sin and death.

    Romans 15:4 (TLB)

    The problem here is that Christ’s death and resurrection had already done away with the deadly effects of sin, pedicated upon faith.

    In other places, Taylor uses wordings that would alarm quite a few readers. For example,

    You illegitimate bastard,[a] you!” they shouted. “Are you trying to teach us?” And they threw him out.

    John 9:34

    Highly literal Bibles render the same text in a less extreme way:

    They answered and said to him, “You were completely born in sins, and are you teaching us?” And they [a]cast him out.

    John 9:34(NKJV)

    Some will find these renderings offensive. They don’t bother me however, as in a real life situation, in the heat of the moment, as it were, an angry mob would certainly not phrase it in the way the NKJV does! I see this as a case of the author adding realism to the narrative rather than deliberately setting out to annoy the reader.

    So, how does The Message fair? The brainchild of the American pastor, Eugene H. Peterson, his motivations for writing a version of the Bible in contemporary English language are best explained in the preface to the work:

    While I was teaching a class on Galatians, I began to realize that the adults in my class weren’t feeling the vitality and directness that I sensed as I read and studied the New Testament in its original Greek. Writing straight from the original text, I began to attempt to bring into English the rhythms and idioms of the original language. I knew that the early readers of the New Testament were captured and engaged by these writings and I wanted my congregation to be impacted in the same way. I hoped to bring the New Testament to life for two different types of people: those who hadn’t read the Bible because it seemed too distant and irrelevant and those who had read the Bible so much that it had become ‘old hat

    As a qualified pastor, Peterson would have been reasonably familiar with the original Hebrew and Greek languages underpinning the Old and New testaments, respectively. Taking about a decade to compile, Peterson also subjected the work to the trained eyes of a small committee of Old and New Testament scholars, the names of whom are found in the introduction to the work.The Message first appeared in 2002 in its complete form.

    Title page of ‘The Message.’

    If the TLB is a loose paraphrase, then The Message is very loose in comparison. Consider this passage from Genesis 1:

    1-2 First this: God created the Heavens and Earth—all you see, all you don’t see. Earth was a soup of nothingness, a bottomless emptiness, an inky blackness. God’s Spirit brooded like a bird above the watery abyss.

    3-5 God spoke: “Light!”
            And light appeared.
        God saw that light was good
            and separated light from dark.
        God named the light Day,
            he named the dark Night.
        It was evening, it was morning—
        Day One.

    6-8 God spoke: “Sky! In the middle of the waters;
            separate water from water!”
        God made sky.
        He separated the water under sky
            from the water above sky.
        And there it was:
            he named sky the Heavens;
        It was evening, it was morning—
        Day Two.

    9-10 God spoke: “Separate!
            Water-beneath-Heaven, gather into one place;
        Land, appear!”
            And there it was.
        God named the land Earth.
            He named the pooled water Ocean.
        God saw that it was good.

    11-13 God spoke: “Earth, green up! Grow all varieties
            of seed-bearing plants,
        Every sort of fruit-bearing tree.”
            And there it was.
        Earth produced green seed-bearing plants,
            all varieties,
        And fruit-bearing trees of all sorts.
            God saw that it was good.
        It was evening, it was morning—
        Day Three.

    14-15 God spoke: “Lights! Come out!
    Shine in Heaven’s sky!
    Separate Day from Night.
    Mark seasons and days and years,
    Lights in Heaven’s sky to give light to Earth.”
    And there it was.

                                                                                                           Genesis 1:1-15

    Or consider Psalm 23:4 in The Message;

    Even when the way goes through
    Death Valley,
    I’m not afraid
    when you walk at my side.
    Your trusty shepherd’s crook
    makes me feel secure.

    Psalm 23:4(MSG)

    Death Valley? Where? In California(just west o’ Vegas ken)? Whacky!

     

    In other places, Peterson’s Message appears to water down the convicting words of Scripture. Consider 1 Corinthians chapter 6 in a good literal translation of the Bible;

    Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor [a]effeminate, nor homosexuals, 10 nor thieves, nor the covetous, nor drunkards, nor revilers, nor swindlers, will inherit the kingdom of God. 11 Such were some of you; but you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus Christ and in the Spirit of our God.

    1 Corinthians 6:9-11 (NASB)

     

    Now take a look at what the Message has to say:

    Don’t you realize that this is not the way to live? Unjust people who don’t care about God will not be joining in his kingdom. Those who use and abuse each other, use and abuse sex, use and abuse the earth and everything in it, don’t qualify as citizens in God’s kingdom. A number of you know from experience what I’m talking about, for not so long ago you were on that list. Since then, you’ve been cleaned up and given a fresh start by Jesus, our Master, our Messiah, and by our God present in us, the Spirit.

    1 Corinthians 6:9-11(MSG)

    It’s not quite as explicit is it? Indeed, it appears quite vague in comparison to the NASB wouldn’t you think? This is not meant to villify Peterson’s Message but only to highlight that with paraphrases you lose accuracy, specifics and the like.

    So both the TLB and The Message, despite being quite brilliant in places, also create confusion here and there. That is why it is very important that you do not use such literature as your primary Bible. To establish doctrine, you need to stick close to the letter of the law, as it were. Both these paraphrases are good commentaries, nothing more, nothing less.

    I do have a tendency to prefer the TLB overThe Message though. This is an entirely personal choice. My reasons for preferring the former over the latter stem from its slightly more conservative presentation of the Biblical narrative. There is a case for mantaining the historical setting of the Bible. It was written in a different age to our own. This doesn’t mean it no longer has value to us today; far from it, its moral values never change, but it is simply a fact that these stories were forged in antiquity and that is where they should stay- for the most part anyway. The Message, for me, is over done, reads too much like a novel, has no cross references or footnotes that one normally expects to see in a ‘real’ Bible. I don’t like Peterson’s use of the word ‘Master‘ to represent Jesus either. It makes Him out to be like some kind of Jedi Knight.  The Living Bible(TLB) is more conservative in many ways. For example, it uses the name Jehovah quite often to denote the Godhead. I like that name. And it’s entirely legitimate.

    In the end though, the world is a better place because of these paraphrased overviews of the greatest story ever told. No doubt they will help bring people to Christ and that’s the most important thing of all.

    Use them but don’t abuse them!

     

    Neil English has written a 660 page historical work, Chronicling the Golden Age of Astronomy, showing how extraordinary individuals often used ordinary equipment to glean new insights into the nature of the heavens.

     

    De Fideli.

    The King James Bible in the 21st Century.

    Some Bibles in the KJV tradition, from left to right: The Modern English Version(MEV), the Jubilee 2000 Bible, the New King James Version(NKJV) and the original King James Version(KJV).

    O sing unto the Lord a new song: sing unto the Lord, all the earth.

     Sing unto the Lord, bless his name; shew forth his salvation from day to day.

    Declare his glory among the heathen, his wonders among all people.

    For the Lord is great, and greatly to be praised: he is to be feared above all gods.

    For all the gods of the nations are idols: but the Lord made the heavens.



                                                                                                                    Psalm 96:1-5 (KJV)

    For over four hundred years, the Authorised King James Version(KJV) of the Bible, arguably the finest work of English prose ever created, has filled the spiritual stomachs of milions of Christians across the English speaking world, through war and peace times, booms, recessions and depressions. When one thinks of a ‘Bible’ it is the KJV that most people bring to mind first. Its influence on western civilization, in particular, has been incalculable, inspiring literary genuises like William Shakespeare, Robert Burns, Seamus Heaney, T.S. Elliot, VS Naipaul, C.S. Lewis, Raymond Chandler and P.D. James to name but a few. The austere beauty of its composition found its way onto the lips of such eloquent speakers as Abraham Lincoln, John Wesely, Theodore Roosevelt, Ronald Reagan and Dr. Martin Luther King. And high above the Earth, the Apollo 8 astronauts recited the Book of Genesis during Christmas 1968, as they courageously plyed the seas of outer space on their way to the Moon.  Its lofty, passionate language was considered essential reading for any English-speaking man or woman wishing to acquire a well-rounded education. Over a billion(perhaps as many as 2 billion) copies of the distinguished Bible have made their way into homes, libraries, churches and hotels scattered throughout the face of the Earth.

    In commissioning the new translation of the Bible in “ploughman’s English,” King James VI of Scotland (and the 1st of England), used it to help cement the crowns of both nations, uniting both Puritans and Anglicans under a common ecclesiastical heritage. Although much of the language of the KJV is now out-dated, with some word meanings having completely changed with the march of time, it is still cherished by an adoring legion of Bible readers from both the Protestant and Catholic traditions.

    Because the English language is constantly evolving, scholars have endeavoured to up-date the KJV  so that it would appeal to a modern readership. In this blog, I wish to discuss a modest sampling of such efforts, including the New King James(NKJV), the Jubilee 2000 and the Modern English Version( MEV), all of which show great deferentiality to the Authorised Version, and formulated using much of the same underlying manuscript tradition.

    But before embarking on an analysis of these newer Bibles, I would like to provide a few reasons why all Christians should read the KJV through at least once in their lives. Firstly, its language is unchanged since it was last updated in 1769 (the original 1611 version is almost unreadable in comparison) and so what you are reading now is what your forebears also read. There is no danger of it being altered or updated to conform with modern culture(which unfortunately has become a dangerous trend with some modern translations). It thus provides a timeline uniting previous generations to our own. Secondly, its poetic qualities are second to none. Created to be read out loud, its words resonate whenever a passage from it is recited. The Book of Psalms, in particular, is sublime when read from the KJV.

    The KJV is also very precise (or literal), the original committee of translators being very careful to produce a translation which is faithful to the original tongues(Greek and Hebrew)  in which the Scriptures were formulated. That’s why so many older Biblical commentators used it so extensively.

    The KJV appeals to the intellect. If you consider yourself educated and have never read the Authorised King James, you need to remedy this by spending some time with it. Countless proverbs and idioms we still use in contemporary conversation originated with the KJV. Consider some of these phrases, all of which originate in the Old Book:

    The fool hath said in his heart, There is no God.

    Choose life

    Through a glass, darkly

    A law unto himself

    A drop in the bucket

    God forbid

    Holier than thou

    Put the words in her mouth

    The skin of my teeth

    All things to all men

    Bottomless pit

    Pearls before swine

    Scapegoat

    Land of milk and honey

    Suffer fools gladly

    Sodomite

    Eye for an eye

    Fallen from grace

    Blind leading the blind

    Den of thieves

    Phillistine

    Eat, drink and be merry

    Bottomless pit

    At their wit’s end

    In the twinkling of an eye

    Better to give than to receive

    Signs of the times

    Woe is me

    Born again

    The powers that be

    Out of the mouths of babes

    The blind lead the blind

    Let my people go

    My brother’s keeper

    Seek and ye shall find

     

    The KJV is also a historic version of the Bible. If you want to better understand the works of such classic theologians as Charles Spurgeon, Jonathan Edwards and many from the Puritan tradition, such as Isaac Watts, William Williams, Augustus Toplady, Richard Baxter, John Bunyan and other great revivalists, you will understand their mindset better by familiarising yourself with the old King James.

    Many of the hymns we sing at Christmas and Easter, and in our weekly worship on Sunday mornings at Church were written in the King James vernacular. It is also universal in scope, celebrating a very wide international usage across many denominational lines.

    ………………………………………………………………………………………………………………………………..

    An Aside: Read the Bible, any Bible: Jesus said “you will know the truth and the truth will set you free” (John 8:32). This freedom not only entails salvation but also the truth concerning what is going on all around us. The prophet Isaiah warned us 700 years before Christ;

    Woe to those who call evil good, and good evil (Isaiah 5: 20).

    In this dark generation, where cultural Marxism is rapidly gaining a foothold in our societies, there is a moral role reversal taking place before our very eyes whereby we are now accepting of lifestyles and behaviours that were always deemed intrinscally depraved.

    Then came Osmosis. Thence mass deception.

    It’s so important in this wicked age to remain grounded in the truth!

    Reading the Bible is arguably the best way to know and guard truth.

    Trust in the Lord with all your heart,
    And lean not on your own understanding;
    In all your ways acknowledge Him,
    And He shall direct your paths.

                                                           Proverbs 3:5-6

    …………………………………………………………………………………………………………………………….

    The Jubilee 2000 Bible(from the Scriptures of the Spanish Reformation)

    The Jubilee 2000 Bible.

    The Jubilee 2000 Bible was the brain child of the Hebrew scholar, Russell M. Stendal, who came across an old Spanish Bible, first translated from the original tongues by Casiodoro de Reina in 1569. The manuscripts available to de Reina were the same as those used by reformers who compiled the Authorised King James Version and so belong to the so-called Majority Texts(i.e. Textus Receptus). de Reina made use of earlier Spanish translations of both the New Testament(by Francisco de Enzinas) and Psalms (Juan Perez de Pineda). Stendal also had the presence of mind to compare his Spanish-to- English translation with the earliest translation work carried out by William Tyndale, who produced an English translation of large parts of the Bible as far back as the 1530s(for which he was burmed at the Stake).

    Stendal’s translation is very respectful of the Authorised King James Version and in fact, conforms more closely to the KJV than any of the other versions mentioned above. For example, Stendal elected to keep the ‘thees’ and ‘thous’ in this translation because, as he claims in the introduction, “serious doctrinal error can result from the consequences of changing Thee, Thou, or Thy to You or Your. This can cause scriptural promises or directives addressed to the individual to be mistakenly applied to a corporate group. Modern English is ambiguous in this regard and lacks the precision necessary to accurately render the true meaning of the original.”

    I think Stendal has a point to make here. Consider, for example, the passage from the Gospel of John, Chapter 3, in which Jesus talks to Nicodemus(a Pharisee) about being born again. Here’s how the KJV renders it:

    Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.

    That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.

    Marvel not that I said unto thee, Ye must be born again.

    John 3:5-7(KJV)

    Now, compare that to how the NKJV renders the same passage, without the archaic phraseology:

    Jesus answered, “Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. Do not marvel that I said to you, ‘You must be born again.’

    John 3:5-7(NKJV)

    Notice that the archaic English distinguishes between ‘you’ singular (thee) and ‘you’ plural( Ye). Thus the reader of modern translations cannot as easily distinguish singular from plural. Here’s how the Jubilee 2000 presents the same passage:

    Jesus answered, Verily, verily, I say unto thee, Unless a man is born of water and of the Spirit, he cannot enter into the kingdom of God.

    That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.

     Marvel not that I said unto thee, Ye must be born again from above.

    John 3:5-7(Jubilee 2000).

    Personally, I have no problem with the modern renderings, as usually one can discern whether  a “you” is singular or plural from the context of the passage. I do however, like seeing “thee,” “thou” and “Ye,” as they are not in the least bit hard to get used to. After reading a chapter or two of Scripture, you will very quickly assimilate and appreciate them. Besides they have a certain quaintness that appeals to me.

    …………………………………………………………………………………………………………………………….

    An Amusing Aside: In modern Scots, one will often hear “yous” referring to more than one person.

    ” Are yous away out tonight?”

    Sticklers of course, would balk at the notion of using “yous” in any formal correspondence, but at least it does distinguish between singular and plural!

    …………………………………………………………………………………………………………………………..

    The Jubilee 2000 translation also maintains many other archaic words found in the KJV such as “published” which means “announced,” “raiment” which is “clothing,” and “charity” which is love. But in many places, Stendal updates some words used in the KJV which are easily misunderstood in the modern vernacular. For example in Genesis 3:1 the Jubilee 2000 replaces “subtil” with “astute,” when referring to the serpent in the Garden of Eden. This generally works, but in one case where he maintains the word “study,” it can be a bit confusing. For example, consider 2 Timothy 2:15:

    Study to show** thyself approved unto God, a workman that has nothing to be ashamed of, rightly dividing the word of truth.

    2 Timothy 2:15(Jubilee 2000)

    ** The KJV has the old English word, “shew” instead of “show.”

    The trouble is “study” as it is written in this verse of Scripture does not mean “study” as we understand it today. It actually means something like “strive hard.” This passage is better rendered in good, literal versions of the modern Bible, like the NKJV:

    Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth.

    2 Timothy 2:15 (NKJV)

     

    Stendal also outlines in the introduction that all important Hebrew or Greek words maintain the same meaning throughout the entire translation, which makes doctrinal matters very consistent and easy to understand.

    Although the introductory pages of the Jubilee Bible are written in American English, I was pleasantly surprised by Stendal’s use of the original British English the KJV adopts. So, for example, instead of “Savior,” which you will see in many other translations, the Jubilee 2000 uses “Saviour.” This is a nice touch that other members of the KJV Bible family have not addressed to my knowledge.

    The Jubilee corrects many of the obvious mistakes inherent to the KJV, such as changing the commandment, “Thou shalt not kill” to “Thou shalt not murder” and the erroneous use of “Easter” in the Book of Acts to the correct term “Passover.” Intriguingly, Stendal chose to retain the mythical “Unicorn” in Palm 92 and 29 rather than “wild ox” used in other word-for-word translations.

    Eventhough the Jubilee 2000 is very close to the Authorised King James Version, it is distinct enough to qualify as a sister text to the latter. For example, consider this passage from 2 Thessalonians first in the KJV:

    For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.

     And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:

    Even him, whose coming is after the working of Satan with all power and signs and lying wonders,

    And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.

     And for this cause God shall send them strong delusion, that they should believe a lie:

    2 Thessalonians 2:7-11 (KJV)

    Now consider the same passage in the Jubilee 2000:

    For the mystery of iniquity is already working, except that he who dominates now will dominate until he is taken out of the way.

    And then shall that Wicked one be revealed, whom the Lord shall consume with the Spirit of his mouth and remove with the clarity of his coming:

     that wicked one, who shall come by the working of Satan with great power and signs and lying miracles,

    and with all deception of iniquity working in those that perish because they did not receive the charity of the truth, to be saved.

    Therefore, for this cause, God shall send the operation of error in them, that they should believe the lie;

    2 Thessalonians 2:7-11(Jubilee 2000)

    Note how the phrase “strong delusion” used in the KJV and many other highly literal translations is replaced by “the operation of error” in the Jubilee 2000.

    Throughout the Jubilee 2000 translation, Stendal elected to use the term “saving health” instead of “salvation.” When this alternative rendering was first presented to me, I admit to being  more than a little surprised, but having thought about the term “saving health,” I have now come to appreciate this alternate rendering, as what else does ‘salvation’ from the Living God mean except preservation of health in a body otherwise destined to return to dust?

    The Jubilee 2000 Bible I received has a nice synthetic leather (trutone) cover with a beautiful tree as an icon. It is a very plain, somewhat understated, presentation, which appeals to me, with unusual, light yellow-coloured pages. Another unusual feature of this Bible is the way in which it presents the individual chapters, which are denoted by the Book name and chapter number throughout:

    The unusual rendering of the book and chapter numbers in the Jubilee 2000 Bible.

    The Jubilee 2000 also has an extensive dictionary of Biblical terms at the back of the work, together with a solid concordance for furher study.

    A page from the Bible dictionary of the Jubilee 2000.

    A sample page from the Jubilee 2000 concordance.

    Although I have read through about 50 per cent of the Jubilee 2000, I have been hard-pressed to find any errors, with the possible exception of Psalm 29:6, which has a rather odd phrasing in my copy:

    Note the wording of Verse 6 of Psalm 29.

    However, when I consulted the online Biblegateway Jubilee 2000 text, the wording appears to have been corrected:

    “And He made them skip like calves; Lebanon and Sirion like the sons of the unicorns.”

    Psalm 29:6 (Jubilee 2000)

    Source here.

    In summary, the Jubilee 2000 is a beautifully rendered sister text to the Authorised King James Version. It will only serve to enrich one’s knowledge of this universally lauded Bible and deserves to be part of the library of all those who love the rich tradition preserved in the KJV. Its only weakness, so far as I can see, is that it is a highly personalised interpretation of the Byzantine texts and does not appear to have been formed by a  committee, which increases the likelihood of doctrinal errors creeping in. As King Solomon of old perceived:

    ...in multitude of counsellors there is safety.

    Proverbs 24:6

    That said, I have not uncovered any such deviations, and I happen to think it is an excellent translation that is certainly easier to read than the original KJV, mostly because the archaic use of punctuation in the latter is updated in the Jubilee 2000, which is altogether sensible, making it that little bit easier to navigate.

    The Modern English Version(MEV)

    Title page of the MEV Bible.

    The Modern English Version (MEV) is a translation of the Textus Receptus and the Jacob ben Hayyim edition of the MasoreticText, using the King James Version as the base manuscript. It is published by Passio, a division of Charisma Media Book Group and first appeared in 2014. Unlike the Jubilee 2000, the MEV language has been fully updated into clear, modern(American) English, but still maintains much of the cadence of the old KJV. Just like the KJV, the MEV was created using 47 Biblical scholars derived from a broad, inter-denominational Protestant background, just like the Authorized Version, the identities of whom are listed in the introductory pages of the Bible. As stated in the introduction, the MEV was inspired by US and British army chaplains who wanted their troops to “understand the KJV better,”  but it soon became apparent to them that this fresh translation would actually benefit “the entire English-speaking world.”

    Just like the KJV, the introduction also has a dedication to the reigning monarch of Great Britain and Northern Ireland, Queen Elizabeth II;

    Just like the dedication to King James I of England, the MEV also has a dedication to Queen Elizabeth II.

    Each book of the Bible (66 in all) comes with an introduction which is useful for study and for placing a passage in the correct historical context:

    Each of the books of the MEV Bible have an introduction for setiing historical context.

     

    True to the Authorised Version, the MEV faithfully includes verses which are often omitted by many modern translations based on the older(minority or Alexandrian) manuscripts.

    Consider, for example, 1 John 5:7

    There are three who testify in heaven: the Father, the Word, and the Holy Spirit, and the three are one.

    1 John 5:7(MEV)

    Or the case of the Ethiopian eunuch in Acts 8:

     As they went on their way, they came to some water. And the eunuch said, “Look, here is water. What hinders me from being baptized?” Philip said, “If you believe with all your heart, you may.” He answered, “I believe that Jesus Christ is the Son of God.”

    Acts 8:36-37(MEV)

    However, there are some passages that KJV diehards might be concerned over. Consider this passage from 1 Corinthians Chapter 1:

    For to those who are perishing, the preaching of the cross is foolishness, but to us who are being saved it is the power of God.

    1 Corinthians 1:18(MEV)

    Notice the reference to ” being saved” rather than just “saved” as recorded in the KJV:

     For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.

    1 Corinthians 1:18(KJV)

    I’ve heard some dreadful KJV onlyists (those who believe the Authorised King James Version is the only inspired Word of God) claim that changing “saved” to “being saved” represents some sort of demonic conspiracy to water down the truth of the Bible lol. However, on consulting my NASB reference Bible, I note that the original Greek can be translated either way.

    Much ado about nothing?

    I’d say so!

    Christianity is not a religion, it’s a relationship. And just like any good relationship, it ought to be continual, ongoing, new every morning. I relate more to “being saved” than just “saved,” as this entails an active participation, in harmony with the will of our Lord and Creator, Jesus Christ.

    The MEV large print Bible edition comes with an excellent 132 page concordance for further study.

    Only one error was noted. If you look at Isaiah 58:8 in the MEV it reads:

    Then your light shall break forth as the morning,
        and your healing shall spring forth quickly,
    and your righteousness shall go before you;
        the glory of the Lord shall be your reward.

                                                                               Isaiah 58:8(MEV)

    The problem lies with the word “reward” in line 4. This should read  “rear guard.” There are about a half dozen other incidences in which the same term is correctly translated in the MEV as “rear guard” suggesting that it was a genuine translation error.

    The MEV large print edition is available in a variety of different coloured faux leather covers, all smyth sewn and all possessing a single ribbon marker. This edition is also a redletter (words of Christ are printed in red). The quality is quite good but it appears the MEV is not yet available in premium formats. That said, I believe Passio will shortly provide an updated version of this Bible, which will weed out any remaining bugs with the work. These updates cost money though; to pay for the scholarship as well as the presentation of the Bible as a whole. By purchasing a copy, you can help this fledgling Bible in the KJV tradition go from strength to strength.

    The clear, double-column format of the MEV large print Bible.

    The large print MEV is a nicely made Bible, available in a number of different coloured covers.

    Though this is not a reference Bible, I would highly recommend the MEV to all those who enjoy the old KJV but in a more contemporary, readable, modern English format.

    The New King James Version(NKJV)

    The New KIng James (Holman version); arguably the finest blend of the old and the new.

    The New King James Version(NKJV) is the oldest of the modern attempts to update the Authorised Version. First commissioned by Thomas Nelson in 1975, the NKJV project involved a committee of 130 Biblical scholars chosen from a ‘broad church’ of Christian denominations to create an entirely new translation of the Scriptures from the original Hebrew, Aramaic and Greek texts. True to the original intentions of the KJV translators, who themselves consulted older English translations than the venerable 1611, the committee strove “not to create a new translation but to make a good translation better.” The first edition appeared in 1982 and after some revisions were made, a finalised version appeared in 1984. This is the version which we now have and enjoy.

    Unlike the other Bibles discussed in this blog, the NKJV consulted both the Alexandrian and Byzantine texts to bring its readers the finest Biblical scholarship from both genres, but strove hard to maintain the majesty of the Authorised Version. So, for example, verses 9 through 20 in the last chapter of St. Mark’s Gospel are reproduced but do contain a footnote stating that “Verses 9-20 are bracketed in NU-text as not original. They are lacking in the Codex Sinaiticus and Codex Vaticanus, although nearly all other manuscripts of Mark contain them.” The ” Nu” here refers the older, Alexandrian texts(or the so-called Critical Texts).Likewise, the account of the woman caught in adultery in the Gospel of John Chapter 8 are also quoted in the main texts with footnotes indicating that many of the oldest manuscripts do not contain such verses.

    Many verses omitted in other translations are faithfuly rendered in the NKJV. Consider 1 John 5:7 for example;

    For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one.

    1 John 5:7(NKJV)

    Some have expressed concern that too many changes were made to the NKJV that interfered with doctrine, but having embraced this translation as my go-to Bible for several years now, I have to say that I respectfully disagree with this assessment. Indeed, I think it to be the perfect amalgam of old and new. Specifically, it does not go as far as the MEV in updating the English, but does remove more archaic words than the Jubilee 2000 translation, for example. Personally, I think it’s an awesome translation, one that I favour above all others. What is more, I find it easy to go from the NKJV back to the KJV, but equally so, I find it just as easy to move over to fully modernised versions like the ESV and NIV.

    One of the things that really appeals to me regarding the NKJV(American English) is that the text has not been updated since 1984. Indeed, some commentators have claimed that the language of the NKJV has already been outdated. That said, I have heard through the grapevine that Thomas Nelson have not said categorically that they will not update the text at some time in the future. To be honest, there is hardly any reason to undergo such changes for at least another century lol. If you feel the same way and don’t wish the NKJV to be updated in the foreseeable future, it might help to email them in order to let them know your thoughts and feelings concerning any such updates.

    Another reason why many Christians stick with Byzantine-based texts is that they are, in many ways, less scientifically constructed than those that rely more heavily on the older Alexandrian counterparts. By this I mean, if you were to look at all the sermons used by pastors down the centuries, all the way back to the writings of the early Church Fathers, you will discover that much of their material came directly from the Byzantine manuscript tradition. In otherwords, the Majority texts actually formed the basis of their teachings, unlike the best scientifically constructed texts we see in modern Bibles(like the ESV, NASB and NIV).   What is more, some other Bible commentators have noted that many of the heresies that arose within the early Church, such as Gnosticism, Arianism, Nestorianism, Psilanthropism etc, originated on the Alexandrian side. For these reasons, they claim that it is safer to stick with the western, Byzantine tradition.

    Today, you can obtain beautiful NKJVs(and KJVs for that matter) published by Thomas Nelson, Holman and Cambridge University Press. Unlike the cheap, bonded leather of the older (read 1990s and noughties) copies, the newer NKJVs are adorned with ornate and durable leather-tex, with clear, large-print text(such as Comfort Print), smyth-sewn bindings in either black letter or red letter editions, which can be acquired at relatively little cost. As I affirmed elsewhere, I’m not one for collecting premium Bibles.

    I now have two NKJVs in my possesion. The first is my Holman large print personal size Bible, which I have mentioned in more detail here. I use it while I’m away from home or while attending Church. It is small, compact and lightweight:

    My travelling Bible; a plain NKJV by Holman with minmal footnotes.

    I have another NKJV; the Thomas Nelson Deluxe Reader’s Bible, which only has the text. It was a Christmas gift from my wife in 2018. Though still not a premium Bible, it is very beautiful, with an all-black text with red headings and chapter numbers:

    The protective casing of the Thomas Nelson NKJV Deluxe Reader’s Bible.

    The NKJV Delux Reader’s Bible is guaranteed for life, has a strong smyth sewn binding, gold gilting and two red satin ribbon markers. It contains no notes, concordance or maps of any description(that’s why it’s referred to as a reader’s Bible). Because it is rather large and heavy, I use it entirely for devotional reading at home.

    The plain but beautiful faux leather cover of the Thomas Nelson Deluxe Reader’s Bible.

     

    The title pgae of the Deluxe Reader’s Bible.

    The single column text is in black and has red headings. The layout is very easy on the eye.

    There are many other NKJV Bibles that are even more ornate(but more expensive) but if you really want one with the finest leather bindings, they can be purchased in the region of $70 to $200.

    In discussing these modernised versions of the King James Bible, I have certainly not exhausted all the choices available to the contemporary reader. For example, there is the 21st century King James Bible(KJV 21), which also retains much of the linguistic richness of the Authorised KJV but has updated the spelling and punctuation of the latter, yet like the Jubilee 2000, still retains the ‘thees’ and ‘thous’, etc and which is reportedly( I do not have a copy) easier to read than the KJV itself. More on the KJV 21 here.

    Having said all of this, I feel the Authorised Version of the King James Bible ought to hold a very special place in the library of all Bible believing Christians. There really is nothing like the original in its sheer, towering majesty.

    Of all the Bibles I have in my collection, I have more KJVs than any other translation, not just as a result of purchasing them, but also because they have been gifted to me by friends and family members over the years. And in this day and age, one can acquire truly amazing bargains. Here I would like to showcase just one example; the KJV Large Print Standard Bible, published by Christian Art Publishers(Republic of South Africa):

    The Authorised King James Bible by Christian Art Publishers.

    The cover is a very attractive dark brown LuxLeather in a most convenient lay-flat binding.

    Title page of the Christian Art Publishers KJV Bible.

    This Bible has good quality paper and the words of Scripture are in a very easy-to-read, line-matched, 14 point font size. And though an inch and a half thick, it is surprisingly light weight and easy to carry from place to place;

    The beautiful, large and clear text of the Christian Art Publisher’s KJV.

    This is a red letter edition (words of Christ in red) with convenient thumb indices to quickly locate each of the books of the Bible:

    The Christian Art Publisher’s Large Print KJV has the words of Christ in red and has thumb indices for each book of the Bible.

    And to round it all off, the page edges of this lovely, large-print Bible have a beautiful gold gilding with a single colour-matched satin ribbon page marker:

    The beautifully applied gold gilding on the sides of the pages.

    It has a full concordance and an eminently useful verse finder section, as well a number of full colour maps of the ancient Middle East.

    Best of all, this remarkable edition of the Authorised KJV cost just £20 including shipping!

    Well, this is where I would like to finish this blog on the King James Bible and a few of the other versions based on the same or similar manuscript tradition. I for one will always cherish this masterpiece of religious literature, which has inspired both princes and paupers alike, over many generations, to worship and adore the Ever Living God. I will continue to read it in contemplative silence to myself, or aloud, as it was originally intended, to my wife and children, where its words reverberate around the room.

    Let us end with a solemn prayer inspired form its pages;

    O God All-Sufficient

    Thou hast made and upholdest all things

    by the word of thy power;

    darkness is thy pavilion,

    thou walkest on the wings of the the wind;

    all nations are nothing before thee;

    one generation succeeds another,

    and we hasten back to the dust;

    the heavens we behold will vanish away

    like the clouds that cover them,

    the earth we tread on will dissolve as a morning dream;

    But thou, unchangeable and incorruptible,

    art for ever and ever,

    God over all, blessed eternally.

    Infinitely great and glorious art thou.

    We are thy offspring and thy care.

    Thy hands have made and fashioned us.

    Thou hast watched over us with more than parental love,

    more than maternal tenderness.

    Thou hast holden our soul in life,

    and not suffered our feet to be moved.

    They divine power has given us all things necessary for life and godliness.

    Let us bless thee at all times and forget not

    how thou hast forgiven our iniquities, healed our diseases,

    redeemed our lives from destruction,

    crowned us with lovingkindness and tender mercies,

    satisfied our mouths with good things,

    renewed our youth like the eagle’s.

    May thy Holy Scriptures govern every part of our lives,

    and regulate the discharge of all our duties,

    so that we may adorn thy doctrine in all things

    Amen

    From the Valley of Vision pp 382-3

     

     

    Neil English is the author of Chronicling the Golden Age of Astronomy, which recounts how many amateur and professional astronomers throughout the ages maintained a strong and pervasive Christian faith throughout their careers.

    Post Scriptum:

    More background on the King James Bible can be be found on these links;

    Librarian P.J. Carefoote on the religious and historical importance of the 1611 King James Version of the Bible.

     

    The Making of the King James Bible by Adam Nicholson

     

    The King James and other early Bibles at Wadham College Oxford

     

    Thomas Nelson Publisher’s Miscellania on the King James Bible

     

    President Abraham Lincoln’s Bible:

    Exhibit A

    Exhibit B

    President Ronald Reagan’s opinion on the King James Bible

     

    Problems with the King James Bible

     

    The King James Only Controversy

     

    Which English Translation of the Bible Should We Use?

     

     

    De Fideli.

    The War on Truth: The Triumph of Newtonianism.

    Octavius; magister militum.

    Blog initiated December 31 2017.

    *** New testimonies recently added to the end of the article.

     

    Mair inconvenient truths, ken.

    Mr. Hardglass

     

    For sheer brute force light gathering ability, Newtonian reflectors rate a best buy. No other type of telescope will give you as large an aperture for the money……For the sake of discussion, I have divided Newtonians into two groups based on focal ratio. Those with focal ratios less than f/6 have very deeply curved mirrors, and so are referred to here as ‘deep dish’ Newtonians. Reflectors with focal ratios of f/6 and greater will be called ‘shallow dish’ telescopes.

    Pardon my bias, but shallow dish reflectors are my favorite type of telescope. They are capable of delivering clear views of the Moon, the Sun and the other members of the solar system, as well as thousands of deep sky objects. Shallow dish reflectors with apertures between 3 inches(80mm) and 8 inches(203mm) are usually small enough to be moved from home to observing site and quickly set up with little trouble………..Most experienced amateurs agree that shallow dish reflectors are tough to beat. In fact, an optimised Newtonian reflector can deliver views of the Moon and the planets that eclipse those through a catadioptric telescope and compare favorably with a refractor of similar size, but at a fraction of the refractor’s cost. Although the commercial telescope market now offers a wide variety of superb refractors, it has yet to embrace the long focus reflector fully.

    From Star Ware, 4th Edition ( 2007), by Philip S. Harrington pp 32−33.

     

    To savor stargazing we need to strike a balance between the time, energy, and expense devoted to this activity and what we channel  into other necessary human tasks. A contented evening of stargazing comes with this balance. ‘In medio stat virtus’, or, as this Latin rendition of Aristotle’s maxim has been translated into English, “All things in moderation.’

    Otto Rushe Piechowski

    Sky & Telescope February 1993, pp 5

    The trend towards larger and larger reflectors is indeed exciting, and I can understand the need to keep them short focus( typically f/4 to f/5). But why are so many small ones made with these focal ratios? Such telescopes bring out the worst in the Newtonian design. The 6 inch f/8s and 8 inch f/7s common many years ago, were much better and more versatile reflectors than many commercially available today.

    Alan French

    Sky & Telescope, November 1993 pp 4.

    Newtonian reflecting telescopes are great telescopes for observing Jupiter.

    John W. McAnally, from Jupiter and How to Observe It, pp 152.

    Indeed a high quality Newtonian reflector is a very powerful instrument, fully capable of superb performance in viewing the planets when the optics are kept clean and properly aligned. They have been amng the favorite instruments of serious planetary observers for many decades.

    Julius L. Benton, Jr. from Saturn and How to Observe It, pp 57.

    Newtonian reflector telescopes, apart from their complete freedom from chromatic aberration, can be made with much shorter focal ratios than refractors, usually between f/6 and f/8 so that even an 8 inch reflector is portable and easily affordable by most amateurs. An 8 inch refractor would be financially out of the question for the vast majority of amateurs  and would need permanent housing in a large observatory. As a choice for planetary observation, then, there is a lot to be said for the Newtonian reflector in the 6 to 10 inch aperture range.

    Fred W. Price, from The Planet Observer’s Handbook 2nd Edition, pp 41.

    It is true that such reflectors are considerably less expensive than are refractors of the same size. This does not mean that they are not as good; in fact, Newtonian reflectors are more widely used by more experienced observers than any other type.

    David H. Levy, from Guide to the Night Sky, pp 61

    The simplest, cheapest and overall the most efficient design you could choose to use as a richfield telescope is the Newtonian reflector. As ever, an aperture of 100 to 200mm and a focal ratio of f/4 to f/6 is most appropriate.

    Nick James & Gerald North, from Observing Comets, pp 57.

    It is not proposed to enter upon the controversial topic of reflectors versus refractors. If does not grudge the extra attention to keep a reflector in perfect adjustment, its performance in revealing planetary detail will equal that of a refractor of the same aperture, particularly if it is mounted with an open, lattice work tube, when a further improvement may be derived from the employment of an electric fan  to keep the column of air above the mirror well mixed.Moreover it has practically negligible chromatic aberration, whereas colour estimates made with a refractor are exceedingly unreliable.

    Bertrand Peek, from The Planet Jupiter;The Observers Handbook, pp  37.

    What is “over-expensive”? It depends on your point of view. A 106mm Takahashi flat field quadruplet refractor can be had, without mount, for only a little more than I paid for a high-end 12.5″ dobsonian Newtonian with state-of-the-art optics. If astro-imaging is your forte, the Tak will be the better choice. Don’t forget a high-end mount to go with it. For visual, though? Get real. The Tak will be severely limited–a well-machined, and beautifully-performing SMALL scope that can’t see much. If you buy your scopes for visual use, the Tak isn’t just over-expensive, it’s ridiculous. If you buy your scopes for photography, though, that Tak is an incredible choice.

    Don Pensack from post no. 235 in an online a discussion on Why is Takahashi Overly Expensive?

    Apochomats are expensive, particularly in the larger (repeated word ‘Larger’ omitted) apertures. Object the commonly available designs, reflectors are free of chromatic aberration since mirrors reflect all the colors identically. This means that a good quality reflector with a large aperture can be free of false color and yet provide the resolution and fine scale contrast while still being affordable. These Scopes have issues of their own..

    Jon Isaac, from  post no. 14 in an online discussion entitled, Can An Apochromatic Refractor Use More Powerful Eyepieces than an Achromatic Refractor Of The Same Size?

    So What telescope Should I Spend with My Money On?

    All in all, if you can afford it, and if you have the room to house it permanently in some sort of observatory (perhaps a run off shed), I would say go for a Newtonian reflector of 10 to 14 inches (254 to 356mm) aperture and as large a focal ratio as you can reasonably accommodate……..If you can’t afford a 10 inch then go for a smaller Newtonian reflector. Remember this type of telescope is the cheapest of any but please do not compromise on quality for the sake of size. My second choice for an instrument intended for visual observation of the Moon would be a refractor of at least 5 inches (127mm) aperture…

    Gerald North, from Observing the Moon; the Modern Observer’s Guide (2007), pp 52

     

    A first-rate 130-mm Newtonian is roughly equivalent to a first-rate 102-mm refractor for planetary observing, but superior to the refractor for all other purposes.

    Tony Flanders, former Associate Editor, Sky & Telescope, in an online discussion ( post no. 1837) of the Astronomers Without Borders One Sky Newtonian.

    The Newtonian reflector is a popular choice. Money wise, they are cost effective, and most importantly, you can obtain a large aperture telescope  for a reasonable sum of money…..It is true the Newtonians can come with long tubes if a longer focal length and high focal ratio is required…..Although you will hear it said high focal lengths and ratios( example f/7 etc) are desirable for planetary work, telescopes with a focal ratio of f/5 can be very satisfactory.

    Paul Abel, BBC Sky at Night Presenter, from his book, Visual Lunar and Planetary Astronomy (2013), pp 14/5.

    The best view of Jupiter I ever had was at Peach State with a 12.5″ Portaball on an equatorial platform at 567x (10/10/2010). There was so much detail I tried to find a larger scope in use (no luck, alas). We could see albedo features on Ganymede and Callisto. Amazing what you can see on a night of exceptional seeing. Even when the seeing is not at its best, I find there are often times on any night when a larger scope has an advantage.

    Alan French, from an online discussion (post no.14) entitled Large Telescopes and Jupiter.

    Guan Sheng Optical (GSO) uses high-volume, state-of-the-art, high quality manufacturing and test lines. GSO guarantees diffraction limited performance, but their mirrors typically have a mirror surface quality of 1/16 wave RMS at least, and often better. This very smooth mirror surface results in excellent optical performance with practically no light scatter, while Antares Optics secondary mirrors are 1/15 P-V or better and come Zygo tested;

    Rob Teeter, founder of Teeter’stelescopes.com

    Amateur astronomers and telescope makers have debated from time immemorial the advantages and disadvantages of different telescope designs. In particular, mountains of hard copy and electronic articles are available on the merits of refracting and reflecting telescopes, more recently, apochromatic refractors vs. Newtonian reflectors. This debate has become rather rancorous (Newtonian telescopes as APO “killers” comes to mind.) and unscientific, to say the least. And when all is said and done, in a discourse without loaded words and acrimony, a discussion devolves to one concerning perfect optics. And isn’t this what we all want or wish we had?

    From Ed Turco’s online article: The Definitive Newtonian Reflector.

    Many people shy away from Newtonians because they have exposed optics that get damp and deteriorate. In this respect a good closed tube Newtonian wins hands down over an open tube one, as the tube keeps dew at bay. For the best planetary resolution, a telescope must, must, must must be precisely collimated!!! Also, the optics should be able to cool down quickly by fan cooling. Mirrors thicker than 40mm have serious cooldown problems unless fan cooling is employed. My 254mm f/6.3 Orion Optics Newtonian (plus mirror fan)is the best planetary telescope I have ever used. Some planetary observers line their tubes with cork too, to reduce currents. Many good planetary telescopes are comprehensively ruined by being in a huge unventillated dome with a narrow slit, a concrete floor and a metal dome.

    Martin Mobberley, Author, from his webpage: Telescopes.

    See also his review of the same instrument here.

    Much has been written on the subject of the central obstruction and its impact on fine planetary detail. It remains a hot-button topic in on-line forums, and yet, despite the intensity of the debate, obstruction effects are well understood and fairly simple to quantify. The issue was most elegantly summarized by William Zmek in the July 1993 issue of Sky & Telescope magazine. Zmek’s rule of thumb states that if you subtract the diameter of the obstruction from the objective, you have the equivalent unobstructed instrument when it comes to contrast resolution. In other words, an 8-inch reflector with a 1.5-inch obstruction has the potential to resolve the same low-contrast planetary detail as an unobstructed 6.5-inch scope.

    Gary Seronik, former Sky & Telescope Contributing Editor and Author, from his personal website.

    I have the 12″ Orion as well (Truss, but the same thing otherwise). I have seen two other instances where optical quality on this model was excellent, and my own has perhaps the best mirror I have seen in a mass market dob.Star test with [2]3% obstruction shows an identical secondary shadow breakout, and the mirror had no zones or turned edge, and the smoothness was quite good. In other words, by anyone’s measure, the mirror in my own sample is a really fine mirror. If yours is in the same category for quality, be prepared for some awesome planetary views. The 12″ easily put up better planetary views than my 6″ Astro-Physics Apo and my C14. Views with 31mm Nagler and MPCC Coma Corrector are wonderful (I use the MPCC because it is 1x and while maybe not quite as sharp as the Paracorr, that 1x is important when trying to get the largest field possible out of today’s very expensive wide field eyepieces. I had fantastic views with my 12″ and it is my favorite larger aperture telescope ever. It does everything with excellence.

    Eddgie, from an online thread entitled, First Light with my XT12G.

     

    I tested the scope over a four week period, and found the optics to be very good, to excellent. I star tested the scope extensively, and found the mirror to be extremely smooth, with the slightest under correction.. I couldn’t put a figure on it, GS advertise 1/12 wave. Planetary images were rock hard. I tested the scope against my friend’s 12.5 Inch premium Dobsonian, which sports a “Swayze” mirror, and we couldn’t split the images over four different nights. On one particular night of excellent seeing, I had the magnification up to 500x, without any image breakdown.Our local club Telescope guy ran a series of tests on the optics, the main one being a Double pass Ronchi test, against a certified optical flat. He informed me the mirror was very well corrected, and very smooth. He didn’t believe the price I paid for the entire scope.

    In summary, this scope has been a huge surprise. My experiences with “light Buckets” previously were not great. My intention was to use this scope for deep sky observation only, as I already have a Zambuto equipped premium scope for Planetary work, but it’s a lot more than that. Since purchasing my scope, I have looked through fourteen of these instruments at our club nights, and the images in all of them are almost identical. Guan Sheng seem to be producing a great mass-produced scope.

    Con Stoitsis
    Director
    Comet Section
    Astronomical Society of Victoria Inc
    Melbourne, Australia

    From a review of the Guan Sheng 12″ f/5 Dob (essentially identical to the author’s instrument pictured above). Source here.

    I purchased a 15” Obsession from owner David Kriege on January 12, 2007 and took delivery in the first week of March of the same year. Since that time it has been my principle telescope for visual use. For comparison, I have owned two Takahashis (FS-102 and TOA 130), three Televues (TV85; NP127; TV85 again), a WO 10th anniversary 80mm, an 8” Celestron SC with Starbright coatings and a 6” Orion dobsonian.Despite the demonstrated affinity I have for apochromatic refractors, I had been to enough star parties to learn that aperture ultimately wins…………Those interested in purchasing a larger dobsonian may wonder what you see in a 15” scope. Having compared views with everything from 60mm refractors to a 30” dobsonian, I can honestly say “more than enough to keep you busy for a long, long time”. Globular clusters really seem to take life at about 12” and galaxies are already more than nondescript smudges by 15”. Of course local conditions make a huge difference. I have had nights with a 5” refractor that gave the 15” a run for its money. I have been at star parties looking at a galaxy in the 15”, then wandered next door to a 24” expecting to be utterly blown away by the difference and then been surprised by how little there was. That said, on any given night, the 15” tends to beat the socks off my small refractor nearly every night across the board, from planets to wisps.

    From a review of the 15″ Obsession Dobsonian by Rene Gauge. See here for more details.

    The Oldham optics on this Dobsonian are superb. A number of tests were carried out, the results of which are outlined below. The round airy discs of bright stars appear perfect. Faint stars are fine razor sharp points of light. On nights of good seeing I have been able to see faint diffraction rings around stars. Images snap into focus even at high power.

    After extensive star testing, I could detect no major defects. There was no sign of any astigmatism, even close to focus. The test revealed near perfect correction and very smooth & high contrast optics. Given that the primary mirror is large and fast, and the star test is particularly sensitive, I consider these results to be very good. A particularly impressive aspect is the ability of the optics to handle very high powers. The results of the magnification roll-off test were excellent. First light revealed that the mirror could easily handle forty times per inch of aperture on planets. In good seeing conditions Saturn would reveal a high level of detail and remain sharp at magnifications in excess of 600X, and Jupiter showed no sign of image breakdown at 507X. Under no circumstances have I ever seen Jupiter soften at powers less than 450X. I have even enjoyed good views of the moon at 888X. I have also shared my experiences with a number of experts around the world who believe as I do that the optics are performing to a high specification.

    Nick Koiza, from his review of a David Lukehurst 16″ f/4.4 Dobsonian detailed here.

    Here’s what everyone wants to know. The primary mirror, as with all Zambuto-equipped Starmasters I’ve seen, is a jaw-dropper. Since quoting data on the mirror is often misleading and can cause flame wars, I’ve chosen to leave these out of this review. What I will say is that the Zambuto mirrors have an extremely smooth optical surface, with a near-perfect star test. Running through focus, the Fresnel rings are identical on both sides of focus and evenly illuminated. I can find no zones, no turned edge, and no astigmatism. There is perhaps a “slight” under-correction, however it’s often not even noticeable to me, which could indicate that I might have tested while the mirror was still slightly out of thermal equilibrium. If it is there, it’s very, very slight & I couldn’t begin to guess by what fraction of a wave.

    However, that smooth surface correlates to what I believe to be the most important aspect of visual observing, and that is contrast. In a word – exceptional. The scope shows even the most subtle differences in illumination. There is definitely an emotional response with Carl’s mirrors, an underlying feeling that’s hard to describe, except to say sitting at the eyepiece is more like observing from space rather than the ground. The extremely fine details seen are amazing, and sometimes I seem to subconsciously pick up things that I don’t notice when looking through other instruments, only to go back to my scope & find that I wasn’t dreaming!

    Jupiter usually shows 10 bands and massive amounts of detail within the belts & GRS, as well as the festoons & barges. And being able to see this kind of detail routinely at 400x, and many nights up to 600x is definitely like looking at a photograph. Polar regions & surface detail are visible on Io. Saturn shows the Crepe ring every night, as well as the Encke minima without fail.. Despite the short focal length it is a killer planetary scope. When Mars was last at opposition before the dust storms, picking out surface details was as easy as looking at our moon. In addition both polar caps were easily seen. Phobos & Deimos were also seen. On the planets I rarely use filters, so most of the views described above were natural.

    No matter the conditions, the Trapezium easily breaks into 6 components, even at very low magnifications. The detail level seen in M42/43 is far better than any photo I’ve ever seen, from low-power views that show the entire nebula, to using a binoviewer at 500x on the Trapezium vicinity that reveals details in the nebula, which are reminiscent of the structure seen in cumulo-nimbus clouds.

    With globular clusters, “resolved” takes on a new meaning & the scope provides “in your face” visual observing! Obviously M13 & Omega are completely resolved. One of my favorite globulars is M92 because of the super-dense core that seems to go on forever. One night I decided to push the scope to what our group likes to call “silly power” & view M92 at 700x. WOW – the core showed a tremendous amount of resolution, but again it’s so dense I couldn’t quite get it to go all the way. M13 at this power was like looking right through it to the other side. And I can’t forget the extra-galactic clusters, G1 & G2 in M31. G1 actually started show resolution at about 500x. Another extra-galactic object is NGC 604, the giant HII region in M33, about 2.5 MLY away. At 700x I can see much structure & filaments within the nebula. Seeing that in real time is spectacular.

    Most galaxies within the local group show quite a bit of structure, knotting, & dust lanes. Those more distant objects do reveal detail well above being mere smudges. Many Virgo galaxies show spiraling. Every component of Stephan’s Quintet is always visible, and much easier to see than in many other scopes of similar aperture I’ve used. NGC 7331 is stunning. Closer neighbors like M51, M31, M33, M81/82, M104, NGC 4565 & NGC 891 take on photographic qualities in the eyepiece. I’ve been able to determine the rotational direction of a galaxy that NSOG stated was over 500 MLY distant. The scope is also quite capable of hunting the faint Abell planetary nebulae & galaxy clusters, and with an H-Beta filter, the Horsehead is a snap with direct vision. These are just a few of my experiences at the eyepiece. In short, once the mirror has reached thermal equilibrium, it’s like having a 14.5″ f/4.3 APO. Tight, pinpoint stars sharp across the FOV, and a nice “snap” to focus – there’s no mistaking it. The low f/ratio provides a nice wide field, at least for a scope of this size. I can get 1.4* with the 31 Nagler & using the Paracorr which boosts the focal length from 1584mm to 1822mm. (1.6* without it) Not a bad FOV for a 14.5″ mirror.

    From a very happy and experienced owner of a 14.5″f/4.3 Starmaster Dobsonian. Details here.

     

    Like every Sky-Watcher scope I’ve tested, this one arrived perfectly collimated out-of-the-box, and has held its collimation over the period I’ve been testing it. This speaks highly of the mechanical integrity of the scope, and alleviates the beginner’s greatest anxiety about Newtonians. No doubt the scope will require collimation at some point, but if it can make it to Canada to from China without losing collimation, it should be pretty stable.

    I tested the telescope under the stars on four different nights, exploring a wide range of objects. Well, actually, one night and three mornings, as I was unable to resist the lure of using this scope on my old favourites, Jupiter and Saturn, currently in the predawn sky. I also spent time looking at the Moon, Mars, and Venus, favourite double stars like Epsilon Lyrae (split easily at 120x) and Rigel, and deep sky showpieces like the Ring Nebula and the Orion Nebula. All were well shown, as one would expect in a good quality 150mm scope. The supplied eyepieces, 25mm and 10mm “Super” modified achromats with 50° fields, performed quite well, yielding magnifications of 48x and 120x. This scope showed that it can handle much higher powers easily; I found myself using a 6mm eyepiece (200x) on the Moon and planets most of the time. Fans of deep sky objects will probably want to add a 2″ eyepiece to take in the wide field of view this scope is capable of.

    As Terry Dickinson says in NightWatch, “There may not be a perfect telescope for the beginner, but the closest thing to it is the 6-inch Dobsonian-mounted Newtonian reflector.” The Sky-Watcher 150mm is an excellent example of this breed, at a very attractive price. My wife and I usually donate a telescope to our favourite charity to auction off each year, and this year this scope is our choice. Highly recommended!

    Source here.

    I put together one of his 6″ f8 telescope kits with the help of my kids. It’s still one of my favorite scopes. These days, I lend it to people who have shown an interest in astronomy, but can’t afford a telescope.

    Barry Fernelius, from this online thread discussing Stargazer Steve’s kit ‘scopes.

    Changing technologies have meant that amateur telescope making has largely been replaced  by the purchase of accessible high quality commercially produced instruments, but the Western world’s passion for the night sky is as strong as ever, and long may it continue.

    Dr. Allan Chapman, from an essay entitled: The First Astronomical Societies, Astronomy Now, January 2018, pp 49.

     

    Optical quality matters, but these days it’s usually not the main problem. Most of the commercial mirrors I’ve evaluated in the past 10 years have been pretty good — a few have even been excellent. That’s not to say there aren’t duds out there, but if your telescope isn’t performing, the items that top this list are more likely to be the reason.

    Gary Seronik, from an online article entitled: Five Reflector Performance Killers.

    In this department of astronomy, the names of Herschel, South, Struve, Dawes, Dembowski, Burnham, and others are honourably associated and it is notable that refracting-telescopes have accomplished nearly the whole of the work. But reflectors are little less capable, though their powers seem to have been rarely employed in this field. Mr. Tarrant has lately secured a large number of accurate measures with a 10-inch reflector by Calver, and if care is taken to secure correct adjustment of the mirrors, there is no reason why this form of instrument should not be nearly as effective as its rival.

    W. F. Denning, from Telescopic Work for Starlight Evenings (1891), pp 290-291.

    Since about a month this telescope is parked in my garage.
    It is a Newtonian of 158mm aperture and a focus of 1240mm.The primary and secondary mirrors were made by David Hinds of UK.The telescope was home-made by my friend Tavi aka Erwin.Because he have other commitments, I was offered to give it a ride. I used the oculars seen in the second picture, from left to right: HM 6mm, Galilei – 50 mm, Galilei – 9mm , Baader Classic 6mm Ortho. This are the double.multiple stars observed on 23rd of December. All stars were split except 52 Ori where I believe to see a black space between main star and companion but not 100% sure.I was very pleased to see very well E and F stars in Trapezium.Good telescope, excellent optics, reliable mount……..I continued the testing on 26 of December when I made observations of 36 And, Delta Gem , Theta Aur and Eta Ori. All eas(i)ly split ,beautiful views……………..On 14 of January I targeted 7 Tauri double star. Unfortunately on the rare occasions when the stars were visible, the sky was hazy but still seeing was not better than 5 to 6 Pickering. Like with 52 Ori ,also at 7 Tau double star the Hind telescope showed at 248 x the two touching Airy discs but no black space bewteen them. I have high hopes in good seeing this telescope will split 0.7” double stars.

    Mircea Pteancu from an online thread entitled: Double Stars in the Hind 158mm x 1240mm.

    Visual report on the 12.5” f/6.5 Teeter Dob with Mike Lockwood mirror.

    My eyepiece ‘fleet’ with the 12.5″:

    31mm Nagler 67x

    24 mm Explore Sci 86x

    17.3mm Delos 119x

    12mm Delos 172x

    8mm Delos 258x

    5mm Nagler 413x

    6-3mm Nagler Zoom 344x to 688x

    The first two nights (Tuesday and Wednesday) of observation were very foggy and absolutely dew-drenched – the most dew I have ever seen. Both nights the main mirror dewed up just after midnight – the joys of a thin 1.1” mirror which tracks ambient temperature very well, I suppose….

    Along with the dew was some of the best atmospheric steadiness I have ever experienced. I would place the seeing at 9 to 9.5 (pickering) out of 10. With a 3mm eyepiece (688x) on a 4th mag star near the zenith, the full diffraction pattern was stable and almost unmoving. Unfortunately the transparency was mediocre and, towards midnight, increasingly poor….

    The third night (Thursday) was very transparent and drier, with much more manageable dew but the seeing was extremely poor. The close pairs of Epsilon Lyrae were two touching fuzzballs (the night before you could have driven a HumVee through the blackness between…)

    I looked at a bunch of double stars the first night… I used my Nagler 6mm – 3mm zoom which gives magnifications from 344x to 688x. Close pairs seen were:

    STF 186: sep. 0.8”, mags 6.79/6.84
    wide, dark sky split. The dark space was equal in width to the central discs of both components. very delicate first rings were present at all times…

    A 1504: sep. 0.6”, mags 8.84/8.92
    darkline split. Central discs ‘kissing’… first rings were pretty much too faint to see…

    BU 525: sep. 0.5”, mags 7.45/7.47
    very deep notch. a black or grey line seemed visible at times..

    STF 346 AB sep.0.5” mags 6.19/6.21 This is triple star 52 Arietis. The ABxC pair is at 5” separation… Very nice to see three stars here. The AB pair was a deep notch, again with fleeting glimpses of a line between…

    Dave Cotterell, Madoc, Ontario, from an online thread entitled: 12.5″ f/6.5 Teeter Dob with Lockwood Glass.

    This report details my visual and photographic observations of some sub-arcsecond double stars that have been the subject of a few CN threads the past few months.  This document is necessarily heavy on technical details to support those who may wish to independently evaluate the results.

    Visual observations were made with a 15-inch f/4.5 Dobsonian reflector setting atop an equatorial platform.  All observations were made between September 26th and October 26th of this year with a Paracorr Type I lens (setting no. 1) in the optical train.  In all cases, Pentax lenses were used to achieve the following magnifications:  ‘low’ (5XW; 398x), ‘moderate’ (3.5XW; 569x), and ‘high’ (2.5XO; 798x).

    Imaging was accomplished using an ASI 178MC cooled camera [AVI files; mono mode] in an optical train consisting of a Paracorr Type I lens (setting no. 5) and a 5x Powermate.  The plate scale for imaging was previously determined to be 0.0553 +/- 0.001 “/pixel using calibration stars (n = 10) and 0.0553 +/- 0.002 “/pixel using a diffraction grating with monochromatic red light (n = 8).  Sharpcap 2.8 was used as the image capture software.  Fine focus was achieved using a Bhatinov mask [All-Pro, Spike-a brand] modified to fit over the Obsession UTA.  Separation values were determined using REDUC.  Images were stacked and processed using Registax with final presentation formatting in Gimp.

    Bu 720, 72 Pegasi
    magnitudes:  5.7, 6.1
    position angle:  105 degrees
    separation:  0.575” (orbital elements estimate); 0.505” (last precise measure; 2015)

    The separation data are not in good agreement for this object.  This is, therefore, a good candidate for quantitative scrutiny.

    Visual
    At 398x the object vacillated on the border between elongated and just resolved to two golden-orange disks of similar magnitude in the correct position angle; 569x proved sufficient to show the stars as different magnitude and clearly resolved (but not yet split); a final increase in magnitude to 798x showed the pair as split, again with a golden-orange color and a small difference in magnitude.  The ease of resolution at modest magnification led me to think the larger separation value [0.575”] was more accurate for Bu 720.

    Photographic
    Bu 720 was easily imaged using an exposure of 10 ms [gain = 320].  Four movies were made and separation was measured by three methods using REDUC:  cross correlation of the top 5% of frames using S4 filter; simple measure of a Registax composite; and simple measure of a composite generated in REDUC.  There was good agreement across these methods, giving a measured separation of 0.61”.

    STT 20AB, 66 Piscium
    magnitudes:  6.1, 7.2
    position angle:  176 degrees
    separation:  0.598” (orbital elements estimate); 0.59” (last precise measure; 2015)

    Good agreement between WDS listed separation values.  Should be able to split at moderate magnification.

    Visual
    Low magnification (398x) shows two white stars that are clearly resolved and are oriented in the position angle as stated in the WDS.  Moderate magnification (569x) shows that the components possess dissimilar magnitudes; the pair was barely split about 20% of the time at this power.

    Photographic
    STT 20AB was imaged using an exposure of 12 ms [gain = 400].  Four movies were made and separation was measured by two methods using REDUC: simple measure of a Registax composite; and simple measure of a composite generated in REDUC.  There was good agreement across these methods, giving a measured separation of 0.59”.  REDUC Correlation methods were not useful with this target for producing separation values because of the faintness of the secondary.

    16 Vulpeculae, STT 395
    magnitudes:  5.8, 6.2
    position angle:  127 degrees
    separation:  0.849” (orbital elements estimate); 0.81” (last precise measure; 2015)

    This target possesses a wide discrepancy between WDS values and was discussed at some length in a prior CN thread.

    Visual
    This object was observed as split using an 8-inch reflector at 340x (3.5XW lens).

    Photographic
    16 VUL was imaged using an exposure of 14.5 ms [gain = 450].  Four movies were made and separation was measured by three methods using REDUC:  auto correlation of the top 5% of frames using S4 filter; stacked REDUC reductions; and simple measure of a composite generated in REDUC.  There was good agreement across these methods, giving a measured separation of 0.771 +/- 0.006”.  Previous REDUC autocorrelation measurements of this system using a 2x Powermate [plate scale = 0.143 “/pixel] gave a measure of 0.78 +/- 0.02”.

     

    Mark McPhee, Austin, Texas, from an online thread entitled: Examination of Some Sub-Arcsecond Doubles: Bu 720, STT 495, Bu172AB, STT 20AB, and 16 VUL

     

    Currently, my only objections to the short f/ratios becoming common are that the depth of focus is very short, making focus variability in mediocre seeing a bit more of a problem than in longer f/ratios, and that most eyepieces don’t perform as well at the edges at f/3 as they do at f/5, even when both are Paracorred with the latest Paracorr II at the correct setting. But, that being said, I would still unhesitatingly choose a fast f/ratio at the really large sizes of scope simply because it’s easier and safer to stand on the 3rd step of a step ladder than it is to stand on the tenth (!), and I’ve done that in a 36″ f/5.
    Along the way of large scope progress have come better cells, thinner mirrors, better fans, and better collimation tools. Put those all together, and the performance level of the large scopes seems now to be only limited to the mirror qualities, and there are makers of large mirrors now who put the same quality into their mirrors as some of the better makers who stop with much smaller sizes.
    I truly wish many of you had seen the poor quality large scopes over the years that I have seen. If you had, you’d realize how we truly live in the Golden Age of Astronomy right now.
    Don Pensack, from a thread entitled: Large/Fast Newtonian Mirrors and Quality.
    I thought I wanted a 140 class APO. The image and fantasy of it has been kicking around in my mind for most of the year. They’re such nice looking telescopes – what a telescope is supposed to look like. At a major star party a few weeks ago, I found a beautiful 140 – a very well-known top quality model mounted atop a big G11 and I asked the owner if he would please show me M15 in it. He was proud to do so and we looked. He raved and I was silent. I thanked him and walked back to my premium 16″ Dob. Looked at M15 in the 16 and raved to myself saying I’m so glad I have the 16. For the same amount of setup and money, what a difference!
    Peter Natscher, Central Coast, California, from an online thread entitled; How much increase in aperture to see a difference?
     Ps. Peter is the proud owner of a couple of large premium Dobs and an Astrophysics 175 EDF apochromatic refractor.

    yea sometimes (like this evening) I ask myself too: “why you silly id… buy all this expensive apo stuff???” :)

    Cloudy for the whole day – this evening reported to be one of the most interesting of the year – Io & Europa before Jupiter – together with their shadows and crowned by the GRS. Before 1,5h I saw a break in the clouds and to be fast I just grabed my 8″ GSO Dob and took it out. After 30min cooling another break off – I could see so much detail in the bands, GRS shining in a bright red, both shadows, Europa just beginning to leave the planets disc and – man – I could swear to see a round structure in the band that could have been Io… – best experience for a looong time! :)

    So go get a 8″ f6 Dob – Houston out

    Donadani, Germany, from an online thread entitled; How much increase in aperture to see a difference?

     

     

    Hello Peter [Natscher],

    Hope you are well.

    An 8 inch Portaball with a Zambuto mirror on a tracking platform is going to show you much more than a 130mm telescope, even a Starfire 130EDF. Both of these will be sit down and observe telescopes. If you were not going to get a tracking platform, I would go the refractor route. You will want tracking for dedicated planetary or lunar observing. Shoot, you could roll the dice and get a Sky-Watcher 8″ f/6 collapsible Go-To dobsonian. I have the non motorized version and it has a great mirror, however, your mileage may vary on the chinese mirrors.

    Tony M, from an online thread entitled: 5″ Refractor or 8″ Newtonian for Lunar/Planetary Observing.

    I would take a high-quality 8″ f/6 on a GEM over a 5″ refractor. The GEM will negate all the disadvantages of the Dob. My old Meade 826 easily gives me a sharp, detailed Mars at 400x (conditions willing). I wouldn’t trade it for any 5″ scope ever made.

    Rick Woods, from an online thread entitled; 5″ Refractor or 8″ Newtonian for Lunar/Planetary Observing.

    I may be too late to add my .02, but it should be valuable.

    I have owned a AP130EDF and the GT model. I now own an 8″ f/5.5 Portaball.

    My conclusion: The Portaball rips the APs to shreds. A perfect 8″ mirror over a perfect 5″ lens…no comparison, obviously assuming collimation and thermal equilibrium. Especially since the Portaballs are constructed with fans and other ergonomics to help with the thermal adjustment. And I’m solely talking about visual planetary, since that is almost exclusively what I do.

    Markab,  Kansas City, from an online thread entitled: 5″ Refractor or 8″ Newtonian for Lunar/Planetary Observing.

    One should never lean too heavily on sketchers. Although the vast majority are genuine, some go to an imaging website, study a particular image, and fake a sketch. In this way, they can make a 4 inch peashooter telescope look better than a Hubble image. I’d put more faith in the unlying eye of a CCD camera than any sketch, however elaborate.

    Mr. Hardglass.

    A major reason refractors give images with higher overall contrast than reflectors is that objective lenses may scatter only approximately 2% of the light passing through them. This is why I believe that the high refelectivity coatings that are now applied to many astronomical mirror surfaces are so important. With 95% reflectivity, not only will they give somewhat brighter images but they will also greatly reduce the amount of scattered light, so improving the overall contrast. A high reflectivity coating is well worth having even at an additional cost; not only will the telescope perform better but a second advantage is that the mirror surface allows far less moisture to penentrate and is likely to last perhaps 25 years before it has to be recoated. I have a 10 year old Newtonian whose mirror was one of the first to be given a high refelctivity coating and it still looks like new………The overall design of the telescope will affect the overall contrast as well. It is impossible to beat a well designed refractor, but Newtonian telescopes, where one observes across the tube assembly to the far wall, are almost as good.

    Ian Morison, from An Amateur’s Guide to Observing and Imaging the Heavens (2014) pp 10.

     

    A Newtonian for All Round Use

    A very good compromise in designing a 200mm Newtonian is to use a focal ratio of f/6, and many such telescopes are sold with this basic specification. The focal length will thus be 1200mm, and the field of view when a low power, wide field, 2 inch eyepiece is used will be approximately 2 degrees. The secondary mirror willprobably be approximately 50mm in diameter, and this would give a percentage of obstruction of 25% and provide full illumination over the central 25mm diameter region of up to 46mm diameter field of view. This is a good compromise, but some manufacturers, such as Orion Optics in the UK allow the purchaser to choose other secondary diameters should he or she wish to optimise the telescope towards planetary (approximately 36mm) or widefield imaging (approximately 60mm). One could even purchase two flats for use depending on the type of observations planned for a given night!

    Ian Morison, from An Amateur’s Guide to Observing and Imaging the Heavens (2014) pp 64.

     

    Yes, I have active cooling for my 10″ Dob. For that scope, a fan in a baffle below the primary works fine. I have an EdgeHD 8″, a SW120ED and a 10″ solid tube Dob, and I know how Jupiter looks in all three. No 7″ APO in the stable, but aperture does count for something. Some of my best views of Jupiter have been through the 10″ Dob during early morning. All of my best views of Jupiter have been through the 10″!

    Sarkikos, from an online review of the Celestron EdgeHD 8 inch SCT.

     

    Making a good 8 inch Newtonian by Toshimi Taki (Japan).

    I think I can speak with at least a little credibility on this subject, having owned numerous large refractors:
    TeleVue 140
    NP-127
    One of only two Christen 6″ f/15 folded Triplets
    Takahashi FC-125
    Takahashi FCT-150
    8″ Alvan Clark
    and having used several other premium 8″, 10″ and 12″ refractors.
    As a recovering “refractor-holic” I still crave their look, fit and finish. And inch-for-inch they can’t be beat. But an 8″ or larger refractor w/mount is a true BEAST to own unless you can leave it permanently mounted. Topping it off there’s that little thing called “COST”!
    Once we started having master mirror makers like Carl Zambuto et.al. turning out mirrors that were simply without compromise, optically – the paradigm shifted!
    A premium 12.5″ reflector today will simply blow away that beautiful old 8″ Clark. My present 14.5″ Ed Stevens mirror produces planetary images that are superior to anything I ever saw in a 10″ Zeiss triplet and pretty darn close to the 12″! And don’t even get me started on comparisons with my 28″ Starstructure w/Steve Kennedy mirror! This scope is fully driven and features GOTO, yet I can set it up, take it down and transport it (easily) all by myself. Try to picture what a 20″ refractor would look like and cost…that’s about what it would take to begin to match the performance!
    Would I love to have a giant TMB set up in a dome behind my house? Sure! But not for ‘performance’ reasons.

    Mike Harvey (Florida), from an online thread entitled: Refractor Versus Reflectors.

    My 6″ refractor [AP 155] will show the arms of M51 from a dark site, but fairly subtly. It’s far behind what my 10″ Dob can do in that area.The inability of the refractor to show much spiral detail in galaxies is probably its greatest drawback as a deep sky instrument.

    Joe Bergeron, (Upstate New York, USA), from an online thread entitled: Refractor Versus Reflectors.

    My advice to everyone wanting better planetary views is is to always spend money on a better instrument, or make their instrument better than it is.   An 8″ f/6 reflector with a high quality mirror is one of the best planetary scopes money can buy.  Period.  Don’t be duped into thinking a 6″ MCT is going to be better. Physics simply do[es]n’t permit it.

    Ed Moreno, from an online thread entitled:8 inch f/6 Dob versus 6 inch Orion Mak on the Moon and Planets.

    I’ve tried a single curved spider in my 8 f7.6, but went back to the straight 4 vane after a year. Didn’t notice even a tiny hint of more fine detail on Jupiter with the curved vane.

    Planet Earth, from an online thread entitled: Curved Spider Vanes?

    The idea of curved-vane spiders isn’t new — the concept has been around for a long time and several designs were detailed in the May 1985 issue (page 458) of S&T. For telescopes up to 12-inch aperture, a curved spider can be a good alternative to traditional 3- or 4-vane spiders. With larger scopes, the diagonal mirror typically becomes big and heavy enough that the greater rigidity offered by conventional spiders or more robust curved ones may be required. I’ve successfully used the design described here in numerous telescopes, including my 12¾-inch. My single-curve spider has the added benefit of being simpler than the ones in the 1985 article, and therefore easier to build.

    Gary Seronik, from his online article: How to Build a Curved Vane Seconday Mirror Holder.

    This is essentially an aesthetic issue. If you don’t like spikes, then go ahead and get a curved vane spider. It does eliminate the spikes. You will see an even glow around bright objects like Jupiter or Venus, and nothing around everything else……..If the spikes don’t bother you, then stick with a straight vane.

    Jarad, from an online thread entitled: Curved Spider Vanes?

    I have put a 6″ APO up against a mass market 8″ f/6 reflector and I can tell you that the 6″ APO overall is a better performer. It is sharper everywhere in the field, had better planetary contrast, and came SURPRISINLY close in terms of deep sky (Globular and Galaxy) performance.

    But this didn’t have much to do with the fact that it was a refractor vs a reflector, but rather more to do with the fact that is is a virtually PERFECT refractor up against a telescope with optics that were only “Fairly good” optically.

    But.. IF you were to put a TOP QUALITY mirror in your scope, along with the highest quality diagonal you could find, you would find that on axis, it would indeed take refractor very close in size to yours to give a better visual image at the center of the field.

    Ed Moreno, from an online thread entitled: Refractor Equivalent to a 8″ Reflector.

    A good 7.1″ refractor is very close to a good 8″ reflector on M13. For planetary resolution most of the time the 7.1″ refractor beats the good 8″ reflector. But, they can be very close on a good night.

    Rich N (San Francisco Bay Area), from an online thread entitled: Refractor Equivalent to a 8″ Reflector.

    As I mentioned earlier in this thread my experience is that a 7.1″ refractor is very close to an 8″ Newt.

    I’ve had my AP 180EDT f/9 APO side by side with a friend’s well made 8″ Newt a number of times. My refractor is more consistant in giving high contrast, high resolution images but on the right night that Newt can give some fine planetary images. For deep sky the views are very similar.

    Rich N(San Francisco Bay Area), from an online thread entitled:Refractor Equivalent to a 8″ Reflector.

     

    I’m not talking about local seeing from night to night. I’m suggesting that if you set up a high end APO and a high end Newt of roughly the same size (maybe a 180mm APO and 8″ Newt) side by side over several nights, the APO (refractor) will more often show better high res, high contrast, planetary detail.

    Rich N(San Francisco Bay Area), from an online thread entitled:Refractor Equivalent to a 8″ Reflector.

    No, a well crafted 8″ reflector with a Spooner f/7 mirror will totally outclass not only 5 or 6″ achros, but 5 or 6″ apos as well. And look at the original posters question again. He was wondering if an 80mm refractor would equal a 6″ reflector or a 100mm refractor would equal an 8″ reflector. No, and it’s not really close. And if you can tie your shoe you can collimate a reflector and clean the mirror once a year.

    And my 6″ $250 Orion 6″ f/8 Dob has run totally neck and neck with my buddy’s Tak 102 on more than a few nights on the moon and planets. And it’s beaten the 4″ apo on some nights. Same result with a TV102 and a Vixen Fluorite 102. And it beats my TV85 and his Tak 78 100% of the time. Myths die hard.

    Quest Do Not Delete, from an online thread entitled.Refractor Equivalent to a 8″ Reflector.

    I routinely compare 6″ APO to 7″ and 8″ Zambuto reflectors – see my sig for specifics. I am a dedicated planetary observer and really enjoy such comparisons.

    Basically, I’ve found that the 8″ Z-mirror when cooled will be ever so slightly better then the 6″ APO. And the 6″ APO will edge out the 7″ reflector. The 6″ APO, an FS152, is a doublet and does not focus all colors to a common point as a matter of design. The blue is thrown way out of focus so the image has a slightly warmer look to it then that of the reflectors. I have often wondered if a triplet was compared to a the 8″ reflector how it would perform. Probably the same as the doublet as resolution is primarily a function of aperture.

    The differences are quite minor in good seeing. But when the atmosphere is unsteady, I prefer the views in the FS152 over everything.

    Peleuba(North of Baltimore, MD), from an online thread entitled: Refractor Equivalent to a 8″ Reflector.

    I have a nice C6-R with a Chromacorr, and a nice 8″ f8 newt with a very fine Raycraft Primary, Protostar secondary, and flocked interior. I can’t recall offhand the size of the secondary, but it’s scaled for my 2″ EP’s, so it’e bigger than is optimal for planets.

    Aestheticly, I find the refractor better, especially on evenings of dropping temps. I know the refractor has to cool too, but the views seem to be sharper sooner, and I never see tube currents.

    The newt does reach deeper, though. But, I generally like to see sharper than deeper for the kinds of things I use the refractor for (planets and clusters). When depth is the concern, I opt for more aperture.

    Under ideal conditions, I’m sure my 8″ newt will out-perform the refractor. But, conditions are rarely ideal, and so the edge goes to the refractor– tends towards better sharpness and better contrast due, I think, primarily to the lack of tube currents and cooling time.

    Apples to Oranges, though.

    Kerry R (Mid West Coast, Michigan), from an online thread entitled: Refractor Equivalent to an 8″ Reflector.

    I will go toe to toe with any 7″ or 8″ APO with my 8″ F8 Newt and my Dan Joyce 8″ f/6.7 Newt. In the end I paid very litte for both Newts, and the 8″ APO owner has paid big time for the 8″ APO and it’s mount.

    Had my share of 5″ to 7″ APO’s and they just dont cut it for such a high price. They do give that super fine snap to focus image, but my well built 8″ Newts can pretty much do the same thing and cost 50x less.

    CHASLX200 (Tampa, Florida), from an online thread entitled; Refractor Equivalent to an 8″ Reflector.

    8″ f/6. You’ll get a little better contrast with an unobstructed scope and imperceptibly brighter image because of light loss on a reflective surface. You won’t have coma on a refractive system, but you won’t have the huge amounts of CA with a Newt that you would have with an 8″ f/6 refractor.

    Aperture, aperture, aperture. That’s what matters. A high quality, thermal controlled reflective system will give up very little to a similar size refractor.

    Deep 13 (NE Ohio), from an online thread entitled: Refractor Equivalent to an 8″ Reflector.

     

    Recognizing that everyone has their own opinions and preferences, here is my opinion and preference based upon 45 years of telescope ownership which by inventory would include something like about 40+ mounted telescopes and numerous guide scopes that would add about 15 or so more to the mix. I have had all types of scopes including both apo and achro refractors, maksutovs, schmidt-cass, newtonian reflectors (both equatorially mounted and dobsonian). While different telescopes are suited for different purposes, my overall preference is the refractor for a number of reasons, in particular the apo refractor of which I have owned 8 different apos. I also enjoy the classic long focal length achro refractor and have extensive use and ownership experience with Unitron refractors………………From my personal experience and in general for most applications my rule of thumb would be that a Newtonian would have to “out-aperture” a refractor by about 33% to be roughly equivalent for most applications. Accordingly the statement that a 6″ refractor is equivalent to an 8″ reflector is for the most part, pretty valid.

    Barry Simon ( New Orleans, LA), from an online thread entitled; Refractor Equivalent to an 8″ Newtonian.

     

    My guess is that a great 5 inch apo refractor would equal an average 8 inch mass produced mirror and it would take a great 6 to 7 inch refractor to equal a great 8 inch reflector. A generic 10 to 12 inch mirror will beat or equal any refractor under 8 inches. These guesses are based on real world observing at most objects. There are always exception.

    Wade A. Johnson (North Central Iowa), from an online thread entitled; Refractor Equivalent to an 8″ Newtonian.

    I have done the side-by-side during a couple of well attended starparties. My well collimated and optically very good C8 performed extremely similar to a very good Meade 6″ APO on Jup[i]ter on a night of exeptional seeing. The refractor edged it out with better contrast. No surprise. Compared to a home made 8″ Newtonian with a small 20% obstruction the images were almost impossible to tell apart.

    So, my answer to the original question is: 6″ refractor.

    I think we are finally well past the myth of a 4″ refractor being “sharper” or “showing more” than an 8″ reflector.

    Contrailmaker, from an online thread entitled: Refractor Equivalent to an 8″ Reflector.

     

    This old and tired conversation just seems to drag on and on, using the same old arguments that fly in the face of both common sense and physics. Drop it…let’s all agree that a 6″ Apo costing $7000 is a bit better than an 8″ F5.9 reflector costing less than $1000.
    Which one would a sane person on a budget buy?

    Covey32 (Georgia, USA), from an online thread entitled: Refractor Equivalent to an 8″ Reflector.

    I would politely disagree to this. I looked through an excellent 5″ apo (my old Tak TOA-130S) and a very good 8″ Newt (8″ f/7) at Jupiter and Saturn. My Tak was soundly beaten by the views through the 8″ Newt.

    Alvin Huey (Greater Sacramento) from an online thread entitled: Refractor Equivalent to an 8″ Reflector.

    If you are talking about a ~5″ Apo like a 120ED, then yes they do give very nice views, but the 8″ f/6 Dob will still show you more detail and at 1/4 or less the price.

    I think the views in the 5″ f/9.4 achro refractor I have are good, and on some nights they really are very good, but I have done quite a few side-by-side comparisons with my 10″ Dob over the past few months and as a result…the frac is back in it’s case in the shed and the Dob is by the back door ready for action whenever there is a break in the clouds.

    RikM, (Gloucester, England), from an online thread entitled: 1st Planetary scope: Refractor vs Dobsonian.

    Quote: “f-ratio is important. A 6″ f/11 might very well best an 8″ f/5 on most typical nights observing planets,” End quote.

    Focal ratio is not relevant it’s the size of the obstruction that matters. So long as the secondary obstruction is under 20% of the primary diameter by area, the scope behaves like an unobstructed instrument. More than 20% and you start to see its effects. The effect you see isn’t due to light loss it’s due to increased diffraction caused by the large circumference of the secondary. This decreases contrast. However, there’s no reason a 25% or even 30% obstructed scope can’t perform very well. Why? If the scope is already a large aperture instrument with good optics then even with a hefty central obstruction it can still show superior contrast and detail. Optical quality and aperture matter more than focal ratio. I see this every time I observe Jupiter at f/4.

    Umadog, (Basel, Switzerland), from an online thread entitled, 1st Planetary scope: Refractor vs Dobsonian.

    My Skywatcher 8″ F/6 Dob beats my 5″ F/8 Apo [Takahashi FS 128] on the planets ……

    post-13701-133877687106_thumb.jpg

    Dweller, (Lancashire, UK), from an online thread entitled: 1st Planetary scope: Refractor vs Dobsonian.

     

    Indeed, this is the point. The reason that beginners should be steered toward f/6 Newts is because this is a cheap way of getting good images. The mirrors are easier to make well and the eyepieces need not be expensive. Coma correctors aren’t necessary. Large (and fast) can be better, but quality is a lottery if you’re buying Synta or GSO, although those manufactures can produce some nice stuff. If you go home-grown you have a much better chance of a good mirror but you’re paying a lot more for it. In the end a lot of this comes down to economics not optics. Finally, there’s the hassle factor. To get the best out of a refractor you don’t have to do anything very special. To get a good view out of a Newt (particularly a big one) you have to plan ahead with cooling and collimation.

    Umadog, (Basel, Switzerland), from an online thread entitled, 1st Planetary scope: Refractor vs Dobsonian.

    If you have been dreaming of the day when the Chinese are able to make a portable 8 inch APO for under a thousand quid, keep dreaming! Seriously, this is not going to happen any time soon because APO-quality 8” ED blanks from the major suppliers (Ohara and Schott) don’t exist and if they did would be hideously expensive. Even if the glass was available, big APO lenses will always need a lot of highly skilled hand finishing along with very careful assembly in a sophisticated cell. The only major suppliers of big APOs today – TEC and APM/LZOS – charge the price of a new BMW for an 8” and if that situation changes it will be because they start charging even more! Then there’s always the Takahashi FCT-200 with a list price of $125,000 (but at least it includes the mount).

    On the other hand, if you dream of getting similar performance to an 8” APO for under a thousand pounds, then dream no longer. Long focus Newtonians have always been simple to make well and with the advent of interferometer testing they can be made to an exceptional level of optical quality. Add in the possibility of a very small central obstruction, easy collimation and just two light scattering surfaces and a long-focus Newtonian has the potential to perform closer to a big APO than almost any other design.

    Roger P. Vine (Welwyn, England), from an online article entitled;Orion Optics 8 inch Planetary Dobsonian Review.

    In a Newtonian 8″ to 12″ with small central obstruction under 20%, very thin spider, longish F ratio above F6, excellent tube construction with well ventilated mirror and a decent flotation mirror cell (no mirror glued to plywood). Shorter F ratios require that the object be exactly centered in the field to avoid comatic aberrations. Also, the shorter the mirror, the more you will have to fiddle with the collimation. The mirror should have the best coating you can afford, avoid cheap coatings that lose contrast over time. Get a coating that you can clean without introducing pinholes. Add to that a smooth functioning focuser and you will have a very effective planetary instrument.

    Roland Christen (founder of AstroPhysics, IL, USA), from his online article entitled: What is the Best Planetary Telescope?

    I’ve compared my ED120 refractor (4.7″) with a number of Newtonians and have concluded that it will match a good 6″ Newtonian in planetary and lunar detail but the additional aperture will show deep sky objects just a little better.

    John Huntley, from an online thread entitled: 150mm Refractor versus 200mm Reflector?

    I am a confirmed dobaholic so the only choice is an 8″ dob between these two. The issue really is that unless spending 10x your budget or more, a 150mm refractor will provide less impressive views of low power faint objects and more faults with high power bright objects than an 8″ Newtonian. I’d also consider it more unwieldy and heavy/difficult to use than an 8″ dob. The one exception to the above is for wide open clusters where the frac will provide slightly more attractive views I think.

    For me at that sort of budget an 8″ newt/dob is about as good as it gets.

    Moonshane, from an online thread entitled: 150mm Refractor versus 200mm Reflector?

     

    I’m a refractoholic but I have to admit that Shane is perfectly right on all counts.

    Olly Penrice, from an online thread entitled: 150mm Refractor versus 200mm Reflector?

    My STS and his have been under the dark skies of Landis a few times since. On one particularly memorable occasion, in May of 2015, our Teeters were out there alongside two world-class apochromatic refractors, the FS-128 and the comically coveted AP130. Given all the high-end gear, it felt like some star party of the aristocracy. My friend, who knows next to nothing about telescopes, was on hand. How could he possibly fathom the privilege of looking through such fine gear. Not until several years in the hobby, did I get my first eyepiece time with an Astro-Physics refractor or a Newtonian with Zambuto optics. There was, in fact, a 5th telescope on hand: a 4.5” Tasco — hey, every aristocratic star party needs a peasant scope. The FS-128 owner kept trying to pawn off the Tasco to my friend but he refused. (My friend later regretted not taking it). The modest scope did show Saturn nicely. In fact, on this night the seeing could not have been better. We were all treated to awe-inspiring views of the ringed gas giant, arguably the best I’ve ever had. On this night, Saturn would have looked great in about anything, but the two best views were to be had by the Teeters. My friend, who had no skin in the game (so to speak) or reason to be biased, attested to the “cannon ones” affording the best views of Saturn.

    Daniel Quirin, from his online review of the Teeter STS18 (8″ f/6) Newtonian.

    Once again, these Newts just floor me! Refractors will always be beautiful, but it’s hard to justify a $250,000 refractor to an $8,000 Newtonian that’s beating it. The fact is, is that if you dial the Newt right, your gonna win. Pons has been observing planets for 50 years. He’s earned the right to decide what he thinks is best and he’s got the best of both worlds to prove it.

    When I asked him which scope he liked better on planets, he said the Newt was king, hands down and it’s as simple as that. He has no shame in saying so, d[e]spite the fact that he’s spent a good part of his life and a lot of money building the refractor.

    People always try to challenge me in a debate. Then they look through one of these Newts and they’re quickly silenced. Pons always told me that they’ll always try to argue, but they’ll quietly go back to their garage and start trying to build a perfect Newtonian on their own.

    Daniel Mounsey from an online thread entitled: Refractor vs. Reflector?

     

    Yes, a 4-5″ APO will be very good, but the smallest detail it will resolve on a planet is around the 1 arc-second diameter mark. Resolution is tied intrinsically to aperture. It doesn’t matter how good the optics are or whether you’ve got 99.8% Strehl ratio optics etc, it won’t (indeed can’t) do better than this.

    A clean, well-cooled and collimated, say 10″ f/6 or f/7 Newtonian with quality optics around 1/25th wave RMS mark and a secondary obstruction <20% in near perfect conditions will do twice as well as the 5″ APO in the same conditions — ie in the smallest detail to be potentially visible. It will probably cost little more than half as much. If the seeing is mediocre or poor there will be little difference in detail visible except in those occasional moments when clarity prevails for a moment or two — and the Newtonian wins again. The larger ‘scope will produce a significantly brighter image that will take much more magnification before it becomes unacceptably dim and uncomfortable to view.

    Don’t get me wrong, refractors are beautiful telescopes inch for inch, but they are practically limited in aperture. (well they are aperture-limited by the depth of your pockets I guess). Aperture of the primary mirror/lens is the prime determiner of how much detail is potentially visible in a planetary image.

    In poor, mediocre or average conditions a SCT of similar size to our Newtonian will perform about as well on planetary detail as the Newtonian. In very good conditions or excellent (rare) the Newtonian will produce a somewhat crisper image due to the much smaller secondary mirror used. It is a simple matter of physics due to the size of the secondary obstruction and the wave-nature of light. Increase the secondary mirror size and you push more light out of the Airy-disc and into the surrounding diffraction pattern. As Foghorn Leghorn said to the young chicken-hawk “Son yer can argue with me, but yer can’t argue with figures” — and that’s a fact, not an opinion!

    Also, it is a simple fact of life that in a typical commercial SCT used with a diagonal, you need to get 5 optical surfaces right for it to work well. In a Newtonain there are only two.

    If you are looking for a quality, visual-use, portable “APO killer” for an Eq6 mount, get yourself an 8″ f/7.5 Newtonian with a 25mm secondary. Longer focal length Newtonians are easier to collimate and much more forgiving of slight errors. Additionally, they are much easier to fabricate! Your eyes (and bank-balance) will thank you for a long time — it will flog the pants off any 4″ APO on any subject in the night-sky save perhaps ultra-wide field viewing. The image will be 4x brighter at a given magnification and will show twice as much detail in the right conditions.

    Les D (Australia), from an online thread entitled; PLANETARY VIEWING ?? -aperature rules?or telescope type?

    Unless your mirror is absolute and total trash, the reason is cool down, collimation, or seeing. Sounds like you took care of cool down and collimation so… Seeing.

    Big scopes are able to resolve more, so they are subjectively more affected by poor seeing. I noticed this last night. I set up my 15″ next to so[me] nice Apo refractors, and stars looked better in their scopes. Seeing was exceptionally bad for me last night, stars were bloated little orbs over 150x, but they looked fine in the refractor. Peering at the moon, I didn’t see that shimmering you describe, but defocusing a star I could see very very fast upper air movement.

    Now I know my mirror is not trash, it’s actually quite good and I’ve seen pinpoint stars at 300x in it and views of Jupiter that look like photographs. Last night, I couldn’t even see the GRS. So on nights of bad seeing, a small scope will be subjectively better because it isn’t big enough to resolve the poor seeing, at least not as well as a larger scope. That’s normal.

    I[t] beat the pants of[f] the refractors on M13 though, and the Leo triplet, and M104, and M51… Shall I continue the list?

    Brian Carter (Atlanta, Georgia), from an online thread entitled:Jupiter in my Dob vs Refractor?

    Are those little apochromatic refractors really better than reflectors? They certainly have been advertised as such. In fact, refractor manufacturers have always alleged that reflectors are, well… just a little less than the ultimate – workable, useable, but really not first rate – images just a little sour. And in fact, many a view through a reflector confirms the sour image reputation. Views through refractors are invariably sharp and crisp, neat and gratifying to the eye. But are reflectors really a poor man’s telescope, a less than optimum instrument? As you might imagine, I don’t think so. And here is why I think not and why the “super little refractor” thing is just another load of advertising hype……….

    While a Newtonian reflector of aperture and design proportions sufficient to function as a serious instrument for lunar and planetary observing is not going to be as readily portable as a small refractor or Schmidt Cassegrain or Maksutov instrument, such an instrument will optically match or out-perform all other forms of astronomical telescopes inch for inch of aperture in larger sizes. The problem is that such a Newtonian reflector requires slightly more care and consideration in use, but will be considerably less expensive to construct than any of the other telescope types. The point to emphasize here is that the Newtonian reflector is in no way a substandard instrument when compared to other compound reflecting optical systems or refractors. It is every inch the equal of these instruments, and, I believe, in many ways superior. Design the instrument well, construct it out of quality materials and with care, and fit it with quality optics. Give the instrument chance and it will absolutely amaze you.

    Robert F. Royce (professional optician), from his article, Reflector vs. Refractor.

    As early as 1972, the renowned British telescope maker E.J. Hysom conducted a careful series of experiments with mirrors of various diameters and thickness using a sensitive thermocouple. Hysom determined that a 30mm (1.2 inch) thick mirror cools at a rate of 3.3°C per hour, while a 76mm (1.8-inch) thick mirror cools at a rate of only 0.9°C per hour.
    With the aid of a fan these rates could be increased by a factor of three.
    Thomas Dobbins, from an online article entitled: The Recent Evolution of the Planetary Telescope: Part 2.

    An 8″ mirror doesn’t have these thermal stability issues that are fundamental to larger apertures. Cool-down is relatively quick as long as you have a pyrex mirror. An 8″ plate glass mirror with a fan will also cool down quickly.

    8″ f/8 newts (provided they have a solid/split tube design) can be staggeringly good planetary scopes. Wholly apart from the materials costs of refractor glass, you’re more likely to get a perfectly figured optic than you are with an apo. Refractors have more optical surfaces that have to be accurately figured (4 in a doublet, six in a triplet) whereas a newtonian only has one. At f/8, if using a low-profile focuser, the central obstruction is miniscule and the increase in contrast over a shorter focal length newt can be dramatic. Also, using a single-arc two-vane curved spider like a protostar can go a long way towards minimizing overall diffraction. Also at 8″ or less, the flexure inherent in that design is negligible enough not to affect performance.

    Zamboni, from an online thread entitled: OPT 8″ f/9 Planet Pro Dobsonian.

     

    The Astronomers Without Borders’ One Sky Newtonian; an affordable but good quality, ultraportable 130mm f/5 tabletop telescope.

    We have 4 scopes that always see some use. A 8″ F8 Newt (Dob mount), a 111mm APO (actually, a lot of 4″ refractors), a 16″ SCT and a 17.5″ F4 Newt (dob). The 8″ has some of the best optics I have ever had the pleasure to use, a true one of a kind scope. Planets are fantastic through it. Actually, pretty much everything is. But, when I want to look at galaxy clusters or similar, the 17.5″ is the scope. When I want to study the details in planetary nebula or small single galaxies, I like the 16″ SCT. On exceptional nights, the 16 is great on the planets too but those nights are far and few between here in the Great Lakes State (only 1 really comes to mind in the last 10 years…).

    Jason B, (Michigan, USA), from an online thread entitled: 1 inch Apo vs 12 inch SCT.

    Under the stars, this telescope really shines now. It really is nearly the equal of my 10 inch f/6, a ‘scope I have been told by many who look through it, has Zambuto like quality. Planetary detail is excellent. Deep sky is just great. I find myself surprised over and over again by this telescope. The figure on that primary is just excellent. We did not touch what the original guys at Cave Optical did with the figure, we just recoated it. I reviewed this ‘scope on the Todd Gross astro equipment ratings site, and I’ll tell you now what I said then. If you like vintage ‘scopes and you don’t have one of these, try to find one. You won’t be disappointed! 

    Edward Conley, (North Branch, MI, USA), from an online review of a Classic 8″ f/7 Cave Astrola Newtonian.

    FWIW Rolando [i.e. Roland Christen] said the best view he ever had of Saturn was through a 12.5″ Cave – 800x was no problem.

    deSitter, from an online thread entitled: Cave Telescope Estimate of Worth.

    Jupiter on the morning of October 8 2010 by Jason H ( Central Florida, USA); afocal footage from a Criterion RV 8 f/7 Newtonian reflector.

    When I rece[i]ved my 6″ F/8 Criterion RV-6 I was amazed at the detail I could see on Jupiter. Since then I have heard many others say how well their RV-6 scopes performed. Why did these scopes seem to perform so well? How do they compare to “modern”: Newtonians like Zambuto mirrored scopes?

    Jim Philips (South Carolina, USA), on an online thread entitled: Criterion RV-6 Dynascope.

    Well I always like to have an excuse to repost a picture of my restored 1960 or 61 original RV6. Yes the optics are as good as everyone reports. I agree with what others have written that the 6 inch at f/8 is relatively forgiving and if well made performs excellently even with a spherical curvature. After seeing a neighbors RV6 outperform my Astro Physics 6 inch f/8 triplet,(early model), I sold the refractor and restored my RV6 to almost like new condition.

    Bill Nielson (Florida, USA), on an online thread entitled: Criterion RV-6 Dynascope.

     

    Went to my club Saturday nite and happened to set up right next to a gentlemen who was using a 5 inch Takahashi refractor. I was using my 8 inch Orion Intelliscope. We struck up a conversation and soon began swapping scopes on different targets. Now as some of you know, i got the Dob to tide me over while saving fro a premium APO. Well, to make a long story short, my lowly, mas produced mirror beat the state of the art fluorite lens on every single target, planets included. Interestingly, it wasn”t i who first acknowledged this, it was the guy who owned the Tak. He kept bringing his own ortho eyepieces over to my scope, and shaking his head. As a recovering CRF, this was very validating for me. I am really no longer seeing any advantage at all to ultra expensive refractors. Not to mention that, while stunningly beautiful, and well made to say the very least, his scope and mount combo is a boat. Mine was out and ready in under 5 minutes. In conclusion, I am no longer aspiring to get the 4 to 5 inch APO, rather my next upgrade will be a 12 inch newt, which, because of cost, can happen a lot sooner. Personally, at this point, I see refractors as excellent, rugged, grab and go travel scopes. I am quite happy to be in the reflector camp at the moment.
    Jonnyastro, from an online thread entitled 8 inch Newt vs 5 inch Apo.
    Aperture rules and a lot always depends on the seeing which is the great equalizer, but a well made Newt with a reasonably small secondary mirror can be a great planetary scope. The secondary mirror will always lower contrast compared to the unobstructed Apo, but the higher resolution of an 8” brings something to the view that the 5” telescope can’t.

    Snart, from an online thread entitled 8 inch Newt vs 5 inch Apo.

    I just got back from a weekend star party and pretty much had observed the same thing. My well collimated DOB showed more and better than anything that had less aperature. Since I cant afford anything in the APO category, it left me pretty pleased with my equipment…….. VERY encouraging. I guess my homework and the help supplied from CN has led me to the right stuff!

     

    Steve k, from an online thread entitled 8 inch Newt vs 5 inch Apo.
    The hang up over reflector verses refractor seems to originate in the 1950’s-1960’s. Even Patrick Moore will say buy a three inch refractor or a six inch reflector.
    However times and tech have changed. It just takes time for the astro community to accept this. I own a 14 inch reflector and I also own an 8 inch mak. I have also owned a five inch apo. The most used scope is the 14 inch reflector. I have been into astronomy for 30 years, I have been very active and I know my stuff.
    Don’t forget if someone buys an apo for $2000 they want it to out do any other type of scope that costs a third less,their opinion will rely on the cost. It is human nature.
    Gordon, from an online thread entitled 8 inch Newt vs 5 inch Apo.
    It just boggles my mind that a piece of equipment costing in the three hundred dollar range can outdo one costing in excess of 5000 with mount.
    Jonnyastro, from an online thread entitled 8 inch Newt vs 5 inch Apo.
     

    Being a newt guy, I’d agree that an 8″ reflector can beat a 5″ apo refractor. However, I would point out a few things: The newt may require more cooldown time, and it may be more affected by seeing conditions, tube currents, etc. The newt will show diffraction spikes around bright objects unless a curved spider is used, while the refractor will obviously not. The refractor may show a “cleaner” image, but not necessarily more detail. This is especially true if the newtonian has a large central obstruction, isn’t flocked, etc….The great thing about newtonians is that they’re easy to modify. A flocked, collimated, cooled down newt with a curved spider, nice focuser (being perfectly in focus is important on planets!), and good optics will be right on par with an apo refractor of the same aperture minus the secondary obstruction, IMO.

    Erik, from an online thread entitled 8 inch Newt vs 5 inch Apo.

     

    like i always show my students; a 6″ unobstructed, perfect optic is creamed in resolution by a 10″ 20% obstruction 1/10 wave newt:

    http://www.astromart…?article_id=473 (thanks darren!)

    this is why i always wonder when people say refractors are best on planets…..

     

    dave b, from an online thread entitled 8 inch vs. 5 inch Apo.

    KWB said

    like i always show my students; a 6″ unobstructed, perfect optic is creamed in resolution by a 10″ 20% obstruction 1/10 wave newt:
    —————-
    That’s fine, Dave but your skirting the issue. I’ve now been painted into the corner. Can you give the nod to a 6 inch
    F/8 reflector against a 150mm Tak,AP,TMB,etc,?

    if they both cost the same, i would take the 155mm AP.

    if the 155mm AP and an 1/8 wave 8″ newt both cost the same, i would of course take the 8″ newt.

    dave b, from an online thread entitled 8 inch vs. 5 inch Apo.

     

    When I owned an 8″ Mag1 Portaball with a Zambuto mirror, I used to compare the views of the planets through my telescope with refractors. Over a two year period, there were a few refractors that came close to providing better views on a few exceptional nights, but I didn’t find a refractor that could compete head-to-head with my reflector. (The best refractor, the one that came the closest, was an AP 155, if I recall correctly.)

    I now own a 12.5″ Mag1 Portaball (also with Zambuto mirror.) I’m still waiting for the night where the refractors demonstrate their clear superiority. I’m not holding my breath. Under crappy seeing conditions, I’ve seen the phenomena of a refractor providing what its owner called ‘a more aesthetically pleasing view.’ This is another way of saying when the seeing is bad, smaller aperture scopes don’t see the bad seeing as well as [a] large aperture scope. (In this type of condition, one can ‘stop down’ the larger scope and see the same sort of views that are seen by the refractor.)

    When the seeing is good to excellent and when optical quality is excellent, aperture wins every single time. And dollar for dollar, high quality reflectors rule.

    But don’t take my word for it. Check out Gary Seronik’s article “Four Infamous Telescope Myths” in the February 2002 issue of Sky and Telescope. You can also go to star parties and try a few experiments. Under good seeing conditions, take a look at the planetary views through a correctly collimated reflector equipped with a Zambuto, Royce, Swayze, Hall, etc. mirror. Then take a look at the views through a 6″ refractor that’s many times more expensive. I think that the results might surprise you.

    Finally, consider this Mars image, made by Wes Higgins with a 14.5″ Starmaster. In the past, when the optics in most large reflectors were mediocre at best, I believe that high quality refractors provided the best views. Now, with high quality optics readily available in large reflectors, I believe the situation has changed.

    Barry Fernelius, from an online thread entitled, Reflector versus refractor.

    What more and more people are doing right now in France, is to buy those chinese 8″ or 10″ f/5 or f/6 Newtonians, play with them for some time, then have the primary mirror refigured to an exceptional quality for around €1,000 (US$ 1,250) with enhanced reflective coatings. They perhaps add a better focuser and tweak the spider a little bit. After that treatment on a 8″ reflector with 20% central obstruction, a 6″ APO can no longer match it for visual work.

    Rhadamantys, from an online thread entitled, Reflector versus refractor.

    At the risk of beating a dead horse, my experience is that an APO refractor delivers consistently a[e]sthetically pleasing results every time, with detail limited only by atmospheric conditions and aperture. A high-quality, well designed newt can also deliver [a]esthetically pleasing views, with detail limited only by atmospheric conditions and aperture. Everything else being equal, quality aperture wins, every time. Not surprising that (last time I checked anyway) Thomas Back’s personal scope for planetary viewing is….wait for it…. a 20″ Starmaster. Nuff said?

    Gary in Ontario, from an online thread entitled, Reflector versus refractor.

     

    A 130 mm F/5 with a decent mirror and a 2 inch focuser. No CA, much faster than the Mak or the refractor for EAA and very rugged.

    I’ve owned several.. It’s scary sometimes how good they can be. I remember one night under dark skies.. I was doing the low power, wide field thing with my NP-101 and swapped it out for a 130 mm, F/5 Newtonian with the 31 mm Nagler and a paracorr. I wasn’t giving up much with the $200 scope.

    Jon Isaac(San Diego, California), from an online thread entitled: 4″ refractor vs. 4″ Mak.

     

    As John Browning was to argue in his ‘Plea for Reflectors’ in 1867, good silver-on-glass reflectors had tubes about half as long as those of refractors of similar aperture, they had a superior resolving power when used on dim double stars or planetary surfaces and often gave crisper star images, while unlike large aperture refractors, they were not ‘beyond the reach of all but wealthy persons’.

    Allan Chapman, The Victorian Amateur Astronomer, pp 230, (1998).

    James Francis Tennant, for example, had used a Browning mounted With 9 inch (silveronglass mirror) to observe the Indian eclipse of 1868, while in 1872 Joseph Norman Lockyer had one which produced ‘exquisite definition’. The With instrument in the Temple Observatory at Rugby School and one in a privately owned observatory in Sydney, Australia, were found superior to Clark and Merz refractors of similar aperture. By 1890, With’s mirrors were in use in Europe, Canada, Australia, Asia and elsewhere.

    Allan Chapman, The Victorian Amateur Astronomer, pp 232233, (1998).

     

    I find that the ideal planetary telescope is the largest quality aperture that you will use frequently. It can be fast or slow, in terms of f/#, so long as the optics are good. Ideally the primary is not too thick so it can cool and be cooled in a reasonable time. Proper mirror support and achieving and holding collimation are also very important.

    Mike Lockwood (Philo, Illinois), from an online thread entitled: Help me pick a larger planetary scope.

    I think that the ideal set up would be a 10″ F/7 Newtonian reflector on a GEM.

    Stephen Kennedy (California), from an online thread entitled:Help me pick a larger planetary scope.

    My best planet views came from all of my Zambuto and OMI 11 to 18″ mirrors and all were F/5 or faster. On the smaller size mirrors i like slower speeds in the 10″ and smaller sizes.

    CHASLX200(Tampa, Florida), from an online thread entitled: Help me pick a larger planetary scope.
    There is no way a 4″ apo will destroy a larger Newt!!  lol.gif Simple laws of physics are at play here.  My 6″ Newt with a 20% obstruction consistently shows more planetary detail than ANY of my 4′ Apos ever did!!  My former Takahashi TSA102 never performed as well on the planets as my large dobsonians did.  Aperture wins, every time! Small apos really shine in the portability department so they are eminently well suited to quick setup and teardown times.
    Barbie, from an online thread entitled: Help me pick a larger planetary scope.

    I am just not a APO fan in sizes over 4″. 3 and 4″ APO’s are my fav all around small scopes. Once you get into the 5″ and bigger sizes cost become a problem for me and 7″ and bigger the mount needed becomes pricey and big. A bigger Newt is many times cheaper and does what i need it to do. No 7″ or 8″ APO would give me the image at 1100x+ like my 14.5″ and 15″ Zambuto and OMI optics have done time and time again.

    CHASLX200(Tampa, Florida), from an online thread entitled: Help me pick a larger planetary scope.
     
    Last year I was privately discussing splitting some close doubles with a fellow Cloudy Nights member on the east coast. He was using a 175mm apochromatic triplet refractor that cost $20,000. I was using a 10 inch (250mm) Dobsonian that I bought used on Astromart 15 years ago for $240. One double in particular I had split cleanly with my $240 scope which had eluded the expensive refractor. This was due to the greater resolving power of the larger aperture and the more stable atmosphere (better seeing) of my location.
    Jon Isaac(San Diego,California):from an online thread entitled, How much does a secondary affect the view?
    I am not a bino viewer at all, and my particular vision doesn’t do binoculars, thru a telescope or even at the football field. But I do have personal experience comparing an Orion 120mm ED scope and a GSO 8″ newtonian on Saturn one night, probably some 11 years ago now. Hands down, the GSO (an old Meade LightBridge 8, back when they made them) beat the Orion 120mm ED scope on Saturn. The image was brighter and more detailed. I am certain a 10″ would have done even better, so if you think you’re a refractor guy now, a 10″ newt, should you figure out how to configure it, will convert you, for sure. The collimation and mechanics are the tricky things with these Chinese sourced newtonians, but I’m convinced the optics are actually pretty good. Not saying custom, American/European/Japanese mirrors aren’t better, but the standard Chinese mirror these days is really pretty good. Now the mechanicals associated with the scope are often not as good as the optics, so achieving the best views can be difficult to obtain, even tho the optics may, indeed, be quite good. My friend (who owned the 120mm ED) and myself were impressed with the mirror in the Meade LB8. I have a friend with an Orion Intelliscope 10″ and the views through it, at least on-axis cause he doesn’t own a coma corrector, are spectacular — Thor’s Helmet, Sculptor Galaxy, Jupiter, etc.
    Colin in Alabama; from an online thread entitled:10″ Newtonian to upgrate an ED 120
     

    I have owned a 1/2 dozen garden variety XT6/XT8 Dobs over the last 25 years. None of them were anything special, but they were consistently OK. I also simultaneously owned a sensibly perfect 4” APO and a custom 8” Dob with Zambuto optics.

    The 6”f8 Dob consistently gave me better views of all objects than the 4” APO. The 8”f6 Dob consistently gave better views of all objects than the 6”f8 Dob. The 2” difference wasn’t a “wow,” but it was obvious.

    The custom 8” Zambuto equipped Dob gave marginally better views than the 8” Synta Dob in excellent seeing, but the difference in the views was much more subtle than the difference that comes with 2” of extra aperture, which is why I would expect a typical, garden variety 10” Dob would probably give better views of anything than a sensibly perfect 8” Dob and cost much less

    For reference, a complete XT10 costs $600 and is available off the shelf. An 8” Zambuto mirror starts at $1,100 with an 11 month lead time. A Zambuto equipped 8” Teeter starts around $3,300 with a 4 month lead time.

    gwlee (California), from an online thread entitled: Premium mirror versus Chinese mirror.

    Beyond that, the main thing is to get out there and use it. I don’t really worry much about whether a premium 8 inch would out perform my GSO 10 inch because the 10 inch does a reasonable job of doing what I ask of it. I do know that I have been able to split double stars with it that are beyond the Dawes limit for an 8 inch. Some pretty awesome planetary views at 410x.. And deep space.

    Jon Isaac (San Diego, California), from an online thread entitled; Premium mirror versus Chinese mirror.

    I have enjoyed Sky Watchers scopes for 10 years now in almost every circumstance, under light polluted or super dark skies, under ugly or really good seeing, side by side to terrible scopes or world class (Astrophysics) refractors, close the newbies or really experienced observers. They have never disappointed me, when conditions allow, they deliver terrific planetary and deep skies images.

    Javier (Buenos Aires, Argentina), from an online thread entitled: Premium mirror versus Chinese mirror.

    I had a 120 mm Orion Eon for two years. This is a 120mm F/7.5 FPL-53 doublet and probably better optically than your 120mm Binocular Telescope. I recently sold it because my generic 10 inch GSO Dob was the better all around performer and not just by a little. The Dob was better on the planets, it splits doubles not even worth looking at in the refractor. Globulars, nebulae, galaxies, for deep sky it’s a break through experience.

    Jon Isaac(San Diego, California) from an online thread entitled: 10″ Newtonian to upgrate an ED 120.

    After having large aperture Newtonians and Refractors, I would say yes, it’s possible to make a Newtonian as good as a a Mid priced apo.  My current(and final) scope, a 6″F8 newtonian provides refractor like images of the planets and double stars.  Everything snaps into focus and looks as good as in my former 4 and 5 inch apos.  At this point in my life, an arthritic back and knees prevent me from owning anything larger and I like the convenience of a dobsonian mounting. I’ve always said that if I could have only one scope, it would be a 6″f8 reflector.  It’s an outstanding performer and an excellent compromise between aperture and focal length!!

    Barbie, from an online thread entitled; How hard is it to make a reflector as good as mid-price ED or Apo refractor?

    The advantage of a reflector is that it scales to a larger size much more affordably; at small sizes that advantage is much less. That is why you see small refractors and large reflectors.  The notion that a 4-5″ reflector should be the same price as a 10-12″ reflector, though, is an unrealistic expectation. Next to a 12″ dob, a 127mm refractor looks like a kids toy… they are totally different leagues. Make no doubt about it, a 12″ premium dob will blow a 127mm refractor out of the water in every category except wide field views and ease of use. 

    dgoldb, from an online thread entitled: How hard is it to make a reflector as good as mid-price ED or Apo refractor?

    As Danny shows, the real world can be tamed a little or a lot. Cooling and boundary layers, collimation, and a few other variables are within our ability to minimize. In the tropics the real world is, at times, almost “lab like” with very good seeing and modest temperature differentials. So, even though we cannot talk about performance in isolation, we have a measure of control over “real world” performance except for seeing mostly. We can give our ‘poor’ scopes a fighting chance to perform better than they are often assumed to perform…in the real world, of course.

    Asbytec(Norme)(Pampanga, Philliippines), from an online thread entitled, Premium mirror versus Chinese mirror.

    I agree with Norme, often performance is all about location, location, location! What works well in the south, or out west might not be the ideal scope for the NE or other locations. You have to tailor your scope to your location and observing goals/habits to get the best consistent experience. There is no such thing as the perfect scope for any location, observing style etc. If there was we would all have it.

    Richard Whalen (Florida), from an online thread entitled, Premium mirror versus Chinese mirror.

     

    I have a superb TEC200ED and equally superb (optically, mechanically and coolingly…did I just make up a word?) Parallax/Zambuto 11″ F 7 Newt. Other than image brightness and a slight warmth in the TEC’s color tone, there is little difference between them for solar system viewing. Sometimes I prefer the TEC, others the Newt. The only “glaring” difference is the Newt’s diffraction spikes, especially on Jupiter and Mars. But I’ve learned to live with the spikes and ignore them much like I can ignore CA in achromats ( if it’s not too severe anyway), however there are also solutions for that too.

    For me, the key to really enjoying my newts has been great optics & great mechanical and cooling designs. I want my newts to behave like an excellent APO and I’ve found that it is easily done if I pay attention to the big three: optical quality, mechanical design & execution, and cooling design & execution. Everything else is “sauce for the goose” for me (however, I freely admit to being one of those people who have sub-F5-phobia and yes, I am considering seeking therapy for it).

    Jeff B, from an online thread entitled: How hard is it to make a reflector as good as mid-price ED or Apo refractor?

     I have one mount and two great scopes-an APO and a reflector. I usually go a month or so with one and then a month or so with the other.
    After a month with the reflector I’ll switch to the refractor and notice how pretty the stars look all across the field.
    After a month with the refractor I’ll switch to the reflector and achieve higher mag than is possible with the APO.

    I’m not sure I could call one a favorite but I like the refractor for any outreach situation. It just seems easier for the uninitiated.

    Steve O (Wichita, Kansas), from an online thread entitled: How hard is it to make a reflector as good as mid-price ED or Apo refractor?

    I had a mid 1960’s vintage Cave Astrola Deluxe 10″F7 reflector and a GSO 10′ F5 dob and they both showed the same amount of detail on the planets. The ONLY difference was that the GSO showed a little coma whereas the Cave operating at F7 didn’t. They were both outstanding scopes and any differences other than the above noted were essentially splitting hairs. It is quite possible to get a Chinese optic that is outstanding. My current 6″f8 is a testament to this fact. I think over the last 15 or 20 years, the quality control has gotten a lot better and the chances of getting a lemon are far less but I’m sure the occasional one still gets through.

    Barbie, from an online thread entitled: Premium mirror versus Chinese mirror.

     

    I have also found that it’s much easier to find and purchase sensibly perfect (SP) refractors off the shelf than SP reflectors, which are usually only available from a few small custom shops. Custom SP reflectors are very expensive compared to off the shelf scopes. They have longer lead times, and some sizes, 6”f8 for example, are not available.

    Why? I believe that most people are satisfied with the optics and mechanics of production reflectors at 1/10 the cost and don’t want to wait months for delivery, so the market for SP reflectors too small to be attractive to large manufacturers who stay in business by selling people what they want to buy at a price they are willing to pay and do it efficiently enough to make money.

    For example, my factory 8”f6 Dob cost me $300 and was delivered to my front door by a big brown truck within 48 hours of placing my order. My custom 8”f6 reflector with sensibly perfect optics cost me $3,000 and delivery took a year. Its optics were better, but the improvement was subtle, usually requiring side-by-side testing in better than average seeing to confirm.

    On the other hand, the optical improvements to be had from a 10” factory reflector costing $600 are immediately obvious, so more people are inclined to upsize their reflective optics rather than upgrade them. Other people who are basically satisfied with their mass produced factory reflector optics might prefer to spend the same $3K on a SP refractor, not because it’s better than a reflector, but because it complements a reflector so well, it’s available off the shelf, and it scratches the SP itch too.

    gwlee (California), from an online thread entitled: How hard is it to make a reflector as good as mid price ED or Apo refractor.

     

    My personal experience has been that my dirt-cheap 10″ GSO Dob produces better planetary images than my 4″ Apo that cost well over 10 times the price. Yes there is some diffraction, but the increased resolution, brightness and higher possible magnification compensate for this.

    There is definitely a point where a good reflector (probably Newtonian) must overtake any practical Apo (i.e. <=6″ for most mortals). I suspect this point is probably achieved with premium reflectors >9″-10″ aperture.

    JohnGWheeler, (Sydney, Australia), from an online thread entitled: How hard is it to make a reflector as good as mid price ED or Apo refractor.

    As of last night I now have some direct experience relevant to the question at hand . . .

    A seller had got together the parts to build an 8″ F7, had sold it to a second guy who was more of an imager and decided not to go ahead with the build. I was the third in line, and I finally got it put together.

    Parts are an 8″ F7 Zambuto quartz mirror (made in 2016), a 1.3″ 1/30th wave astrosystems secondary with holder and four vane spider, 10″ x 60″ parallax instruments tube, and a moonlite single speed focuser. It also came with a Meade cell that I upgraded to a Aurora precision cell, and I had to get flocking, rings (parallax), and a dovetail plate.

    After two days of drilling, filing, screwing, sticking, and flocking (and probably several other ‘ings’) I now have a fan-bleeding-tastic 8″ F7 Newtonian for something in the neighborhood of $1600.

    I made mistakes along the way. I miscalculated the placement of the spider/secondary, and so had to source a longer bolt for the secondary. I got lucky with some old plumbing parts that serve as a ball joint at the end to pivot the mirror for collimation. I messed up a measurement on locating a hole for the spider, and my flocking job doesn’t look completely pretty, but it works.

    First light was yesterday afternoon on the moon. Seeing was so-so. High frequency fuzz that makes it seem that the focus is always out interspersed with brief moments of stability. Jupiter finally got high enough for a look around 10:30 PM . . . poor to moderate seeing, but WOW! Exactly what you’d expect from these optics. GRS was bang in the middle of the planet, and very obviously off-pink colored. Numerous bands and a big blue barge visible. Brief moments of very good seeing and I was up to ~300x.

    So how does it compare . . . well, it blows my Televue 101 out of the water on Jupiter and the moon. In fact, it blows my old 6″ F8 triplet apo out of the water, and provides nicer contrast by far than I ever saw in my 11″ Edgehd, albeit with less illumination. And compared with my 12.5″ F5 (Zambuto again) Portaball, well not quite as good as that, but the Portaball would still be thinking about cooling when the 8″ was throwing up great views.

    areyoukiddingme (Santa Barbara, California), from an online thread entitled: How hard is it to make a reflector as good as mid price ED or Apo refractor.

    Bigger Newts will always beat out smaller APO’s on cost and image detail on planets if they are built good. Now compare a 8″ APO to a 8″ Newt and the APO is gonna win, but at 20 to 30 times the cost of the Newt.

    CHASLX200(Tampa, Florida); from an online thread entitled; SW MAK 180.

     

    Others will advise a moderate-sized reflector as affording wonderfully fine views of the Moon and planets. The question of cost is greatly in favour of the latter construction, and, all things considered, it may claim an unquestionable advantage. A man who has decided to spend a small sum for the purpose not merely of gratifying his curiosity but of doing really serviceable work, must adopt the reflector, because refractors of, say, 5 inches and upwards are far too costly, and become enormously expensive as the diameter increases. This is not the case with reflectors; which come within the reach of all, and may indeed be constructed by the observer himself with a little patience and ingenuity.

    *My 10-inch reflector by With-Browning was persistently used for four years without being resilvered or once getting out of adjustment.

    William F. Denning, Telescopic Work for Starlight Evenings (1891) pp 38-39

    An amateur who really wants a competent instrument, and has to consider cost, will do well to purchase a Newtonian reflector. A 4 1/2-inch refractor will cost about as much as a 10-inch reflector, but, as a working tool, the latter will possess a great advantage. A small refractor, if a good one, will do wonders, and is a very handy appliance, but it will not have sufficient grasp of light for it to be thoroughly serviceable on faint objects. Anyone hesitating in his choice should look at the cluster about χ Persei through instruments such as alluded to, and he will be astonished at the vast difference in favour of the reflector….. When high magnifications are employed on a refractor of small aperture, the images of planets become very faint and dusky, so that details are lost.

    William F. Denning, Telescopic Work for Starlight Evenings (1891) pp 41-42

    Perhaps it may be advisable here to add a word of caution to observers not to be hastily drawn to believe the spots are visible in very small glasses. Accounts are sometimes published of very dark and definite markings seen with only 2 or 3 inches aperture. Such assertions are usually unreliable. Could the authors of such statements survey the planet through a good 10- or 12-inch telescope, they would see at once they had been deceived. Some years ago I made a number of observations of Venus with 2-, 3- and 41/2 inch refractors and 4- and 10-inch reflectors, and could readily detect with the small instruments what certainly appeared to be spots of a pronounced nature, but on appealing to the 10-inch reflector, in which the view became immensely improved, the spots quite disappeared, and there remained scarcely more than a suspicion of the faint condensations which usually constitute the only visible markings on the surface.

     

    Concerning Venus: William F. Denning, Telescopic Work for Starlight Evenings (1891), pp 151

     

    Coma is essentially negligible at F/8. It’s there, and can be seen in my 2″ widefield eyepieces, but it’s very muted, even compared to my F/6.24 8″ GSO, to say nothing of the multitude of F/5 and faster mirrors out there. The SkyWatcher 6″ traditional dobsonian makes a nice lightweight alternative when I want something quick to setup, but with enough aperture to wow people on the planets and such. The SW6 makes owning a 5″ refractor obsolete, in my opinion, all while providing the great dobsonian stability that handles the West Texas winds so much better than anybody’s refractor that’s not in an observatory, or using a mount that’s ridiculously heavy and expensive (to say nothing of the accompanying 120mm+ ED glass tube). Yes, it will have less thermal stability, like all reflectors compared to refractors, but that’s a problem one might resolve with a cross-mirror fan, and would be a whole lot cheaper to implement than a big mount, ED glass, etc, without affecting general portability very much.

    I like reflectors, and especially dobsonians, for their ease of setup and use. I have always preferred the eyepiece-at-the-top-&-angled kind of design ergonomically, and the general dobsonian design, with the weight at the bottom of the tube, cannot be emphasized enough how wind resistant it is compared to a refractor’s flying in the air like a flag setup. This comparative difference was demonstrated to me Saturday night, when I had out my SW6″ for its maiden sky-voyage and an often-used Kunming 102mm F/7 refractor on the GSO SkyView Deluxe Alt-Az mount. Although it wasn’t very windy that evening, we still had some, and every wind produced a light dance in the refractor, and only a little wiggle in the dobsonian, which dissipated much, much more quickly than the spasmodic gyrations of the image in the refractor.

    I will have to decide if I want to sell my most excellent Z8 and replace it with a GSO-10″-dob-and-Coma-Corrector or not. That’s a different story, and would involve comparing dobsonian performance to 6″+plus refractors, which are, to my line of thinking, insane and off the table, cost and mount options considered. But I believe the stories I’ve read here on CN, that a 6″ reflector can keep up, visually, with 5″ ED refractors. I’ve seen for myself how much better Saturn appeared one evening long, long ago, in a LB8″ dob compared to an Orion 120mm ED scope. No comparison, really, the 8″-er was that much better, so I’m sure one would have to move into the refractor stratosphere to continue competing with dobsonians above 6″, and why I’d never own such a refractor. But the SW6, especially if I can upgrade the rather inferior Synta 2″ rack and pinion it comes with, puts all the performance of a 120-127mm refractor into an easier to manage, more stable package, at a fraction of the cost.

    CollinofAlabama (Texas, USA), from an online thread entitled; Of coma & 120mm ED refractor.

    The best telescopes known to amateur astronomers have a thin aluminum coating supported by glass, diameters considerably exceeding the largest apochromats, and are at their best under dark, steady skies.

    Alan French (Upstate New York, USA), from an online thread entitled, Comparing FPL-53 and CaF2

     

    It is worth remembering that Stanley Williams and Elmer J. Reese, whose names stand very high in the list of students of the planets, did most of the work for which they are remembered with reflectors of less than 20cm aperture. One of the authors(W.S), while at home from college in March 1978, made an independent discovery of a new SEB disturbance with a 20cm reflector. There was nothing extraordinary in the feat; it was simply a matter of looking at the right time and knowing enough to recognize the significance of what was seen.

    William Sheehan & Thomas Hockey, Jupiter, Reaktion Books, 2018, pp 161

    Well after sitting in my living room corner for several weeks after purchase I managed to get out last night with an Orion XT6 dob, now this is the basic one, 1.25″ focuser, no eyepiece rack and just the one eyepiece, lots of eyepieces already so its not needed anyway. I bought this on a whim new for less than what I have paid for a mid range single eyepiece, $300 Canadian taxes included, free shipping. I,m older and weight was an issue so the 6″ made more sense than the 8″ which I owned many years ago so I was aware of the weight and bulk of it, also the 6″ will live in a small upright tool shed I have for gardening stuff. Just lift it out and use it.

    Lots of light pollution where I live so I tend to observe the moon and planets so after adjusting the secondary (it was way too far towards the primary) I turned it onto the moon.

    Well it looks like I got a good one and I came in at 1:30 pm when both it and Jupiter fell behind the trees, tremendous detail on the moon and sharp crisp views, I like a lot of others have over the years got wrapped up in complex and expensive gear so have a night like this for a modest outlay was a delight, I found it really worked well with some of my lower cost eyepieces, higher grade ones made a difference but not that much.

    Binojunky, from an online thread entitled Cheap small Dob Delight.

    +1

    The XT6i was my default recommendation to newcomers who were confident they would enjoy the hobby. Alas, Orion no longer offers the 6″ with IntelliScope. As Binojunky said, enough aperture to open the door to DSO, can handle magnifications I like to use on planets (200x-300x), light, easily carried, etc., etc. It’s also the perfect size for kids who are old enough to “drive” by themselves. My son and I used one when he was ten. He liked that he could collimate it himself, use the IntelliScope computer himself and point the scope himself. He just wished it tracked.

    macdonjh, from an online thread entitled Cheap small Dob Delight.

    I have owned three of each and still have one of each, both Orion. 6”f8 weighs 34#. 8”f6 weighs 41#. 7# doesn’t sound like much, but it’s a major difference for me at this site that requires a lot of tree dodging; 6” is very easy to use here; 8” is almost unusable, which is why I own the 6. Be aware that 6 and 8 weigh about the same with some brands, SW for example.

    Focal lengths are identical, 1,200mm. 6s cools a little faster. All three 6s had a poor a quality 1.25” focuser. It can be adjusted well enough to be serviceable, but requires frequent tuneups. 8s come with an OK 2” focuser. Both are equally easy to colimate to the required tolerances using laser or collimation cap; theory suggests the collimation tolerances are more forgiving on the 6”, but I haven’t noticed a practical difference.

    Optical quality (figure) of all of them were about equal, good to very good, no advantage to 6 or 8. 6” might be easier on inexpensive eyepieces, but I only use expensive EP, so can’t say from experience, but it’s consistent with optical theory.

    With the same LP EP in both scopes, the 6” has a smaller exit pupil, which is a bit more compatible with the astigmatism in my eyes, so star fields seem a bit sharper to me. At the same exit pupil stars are equal[ly]sharp to me in both scopes. I doubt a person without astigmatic eyes would notice a difference.

    The larger 8” is a noticeably better optical performer an all targets, but especially DSOs. Noticeable, but not wow! I also believe the 8s have slightly better motions, but it’s subtle, and most people probably won’t notice the difference if they don’t have the opportunity to use bith scopes side-by-side. For sites where I can carry the scope out in two pieces and leave it in one place all night, I prefer the 8.

    gwlee(California), from an online thread entitled Cheap small Dob Delight.

     

    I was quite lucky when I bought my 6″F8 Synta(Orion) xt6. Its optics are so good that I don’t really need a premium mirror maker to make me anything better since my Xt6 shows a textbook star test and has been lab tested to be of excellent quality. Perhaps the Chinese have really gotten the 6″F8 optics to a very high level of performance and Zambuto knows this which is why he doesn’t make anything smaller than an 8″. Perhaps not, I don’t know for sure but all I can say is that my 6″f8 shows me fantastic views of the planets rivaling those of my apo refractor [100mm f/9 ED], but with a little more light grasp for deep sky objects. About 20 years ago, I had a Bushnell 6″F8 Dob and it was just o.k. Fast forward to the present and my current 6″F8 dob, the difference is like night and day in optical performance and mechanics so I would say the Chinese have improved by “light-years”, at least when it comes to making 6″F8 mirrors.

    Barbie; from an inline thread entitled;Why won’t Zambuto make 6″ f/8 mirrors.Truth Please

    Did a public star gaze on the beach last Friday and Sat night. Took my 6 inch f8 home built dob out there.

    Haven’t done any such gazes in years and back when I did I was hauling out the 10 f5.6 “big dob”.

    Turns out the 6 inch f 8 is the perfect outreach scope as well !

    There was a C8 celestron. A 9.25 something or other cat. A 4 inch relatively fast ED refractor. Some other guy with another C8 ish type scope set up with a display screen and astrophotography.

    Then, off to one side was my little 6 inch F8 Dob.

    A fair fraction of the folks that looked through my scope made a point of saying that they were attracted to the scope and wanted to check it out.

    And I can think of several reasons why. First obviously home built. Not nearly as impossing as the other scopes. Even the 4 inch frac had a serious looking mount. Not complicated looking. Those other scopes with all those fiddly bits and hand controllers and whirling motors are fairly intimidating to the general public I think. And needless to say the astrophoto/display screen scope took that to the next level.

    Not only did it look simple…folks could see it was simple in use. Look at Jupiter say. Then swing around, sight along the side of the tube or use the laser pointer on the tube and bammmm….now we have Saturn….swing around again….Venus….swing around again…Alberio…swing around again…the moon…and so on and so on.

    Need to move the scope to get an unobstructed view of X? Pick it up….move over…plop it back down….bam….done.

    Most people expressed awe that I could “just find” things. But I explained things…simple landmarks in the sky. Albierio….end star of the easy to see Cygnus. M4…sorta between Antares and that other star. M22…forms a parallelogram with the handle and top of Scorpious the Tea Pot. M57….right between those two easy to find stars near easy to find Vega. Explained how Mars, Jupiter, and Venus are fairly obvious targets once you know what you are looking for. And even Saturn with a little care.

    Then a fair number got fairly interested in the home built aspect. Hey, I just bought the optics and built a wooden box ! The side bearings are PCV flanges…look here the focuser is made of plumbing parts….you can do this too…especially with all the info and help on the internet these day….

    Hey, how much does this cost? Ohhh, you can get something like this for around $300. A bit more and you can get an 8 incher ! The 4 inch frac cost about twice that (the tripod alone was $300). The other scope…well, more like $3000 rather than $300. They probably didn’t wanna know what the imager guy had invested.

    As for views? The 9.25 showed a little bit more detail on Jupiter…but it was all a bit washed out to me (probably that large secondary mirror doing that). The six f/8 dob beat everything else IMO. And this is just some random mirror I bought 25 years ago with a bog standard diagonal. Have never even star tested it. And the eyepieces….my $10 Vite 3 element/plastic lens 10 and 23mm plossls.

    End of the night. Put the tube under one arm…grab the handle on the rocker box and walk to the car in the parking lot. Easy peasy.

    I think a lot of people came away less intimidated about telescopes and costs and finding things in the night sky after seeing the little dob in action.

    Starcanoe; from an online thread entitled; Cheap small Dob delight.

     

    I built and enjoyed this 6-inch F/7.3 before I even knew what a Dobsonian was. But it’s really close to that concept. Enjoyed that for a long time, added setting circles and wroth my own calculator program to point at things. Used that for years on planets, clusters, nebulae, etc. It was wonderful! I would take it in my compact car to star parties. Very convenient. Sure, I eventually went bigger… but your point is a good one. There is a LOT to be said for starting out with this size and doing visual.

    TOMDEY( Springater, New York, USA): from an online article entitled: Versatility of a 6″ Newt.

     

    A 6″ f/8 holds a special place in the hearts of us older amateurs. The classic RV-6 Criterion is the poster child for the 6″ f/8s. Many had exquisite optics and the planetary views were quite memorable. I was interfaced with an RV-6 in high school (I graduated in 1970) – the school owned one and it was superb.

    Yeah – yeah, that’s the nostalgia talking.

    Today, with the Dobs, I would say that the modern equivalent is the 8″ f/6. It’s not that 6″ f/8 is any less worthy a telescope than it was 50 years ago – it is still a wonderful telescope to own. But nowadays the 8″ f/6 has such a small differential in price to the 6″ f/8 that it makes sense to get that instead for most folks. Both telescopes share the same 48″ focal length. So both are manageable as far as size is concerned.

    Siriusandthepup(Central Texas, USA): from an online article entitled: Versatility of a 6″ Newt.

     

    I agree with siriusandthepup that while a 6-inch f/8 Dob is a great scope for beginners — and for experienced observers as well — an 8-inch f/6 Dob is even better. The 8-incher is very nearly the same size as the 6-incher due to its shorter focal ratio, and is quite a bit more capable. The only real advantages of the 6-incher are that it’s somewhat lighter and cheaper and significantly more forgiving of poor collimation. But once you learn how to do it, collimating an f/6 scope should take well under a minute in most cases.

    As it happens, my own scope is halfway in between — a 7-inch f/5.4 Dob. It’s a total joy to use, in every way. I can carry it easily in a single trip and set it up in a matter of seconds. Its ergonomics are miraculous — completely stress-free observing while sitting in a standard chair for objects almost from the zenith down to 20 degrees above the horizon. With a 2-inch focuser, it has an amazing widefield capability, fitting and framing objects like the Pleiades beautifully.

    On 90% of all nights it shows almost as much planetary detail as my 12.5-inch Dob. Under dark skies, it shows hundreds of deep-sky objects with ease, resolves at least a dozen globular clusters, and shows a great deal of detail in nearby spiral galaxies such as M33, M51, and M101.

     

    Tony Flanders (Cambridge, MA, USA): from an online thread entitled: Versatility of a 6″ Newt.

     

    I have been using a celestron c102 4″ f/10 refractor for weeknight hour-long observing outings. With the planets well placed they have been getting much more time lately. However, I find the CA quite bothersome (perhaps spoilt with my other scopes Nexstar 8 GPS and 12 inch dob – naturally color-free but more cumbersome to set up than the 4 inch frac).

    I have been eyeing the At102ed as the natural solution to my problem, and a while back was able to compare the views between the two scopes. Another person present at the club outing had a 6-inch f5 reflector with 2 inch focuser and type 1 paracorr.

    The reflector provided best views of saturn and jupiter – bright, sharp and color-free. It was slightly better on globs like M13 (obviously due to the slightly better light grasp). With the paracorr it was also an amazing wide-field instrument. Just a slight step behind the At102 in FOV department, the paracorr-corrected views were brighter and more engaging to me than the At102ed. It displayed all the portability advantages of At102ed, had better color correction, and provided slightly better wide-field performance but with a slightly smaller wide-field FOV.

    Going by memory (as I had not set up the C8 side-by-side that night) I’d rate the views of the 6″ reflector far closer to the C8 than to 4″ refractor.

    I was about to pull the trigger on At102ed, but I found the 6 inch f5 more satisfying. Although a 4″ ed better compliments my existing line-up, the 6″ f5 is a better stand-alone scope.

    eklf (Carrboro, North Carolina, USA) from an online thread entitled: Versatility of a 6″ Newt.

    I am all about aperture most of the time.That being said, my 6″ is a keeperI have seen spiral arms of M51 in it and fanstastic planetary observing as well. Under dark skies it is a very capablle little scope.Even after getting a 15″ I have sometimes used it for conveniece or neccesity and it has not been ” too bad I can’t use the 15″ scenario.It satisfies.Easy forgiving collimation, very quick cool down and super easy to transport.Odds are you will have good to great optics as well. Outside of Quasars it shows all of the types of objects out there.

    aatt (Connecticut, USA), form an online thread entitled: Versatility of a 6″ Newt.

     

    Definite pros and cons to different sizes. Mass produced costs less, though. With 8″ f6 vs 10″ f5, both should be moved in 2 pieces. But the 8″ can moved in one piece if you really need to dodge a tree. Still, you will want more aperture.

    6″ is enough to get interesting views. M13 starts to break up. Planets start to get beef that the 4″ can’t muster. The view is wider. And the scope is portable. But 6″ is mainly a grab n go. If you drive way out some place dark, you will want a 10″ to enjoy the night. Even at home, the 10″ will be much better on planets.

    Stargazer193857(Southern Idaho, USA), from an online thread entitled: Versatility of a 6″ Newt.

     

    Webster telescopes has a 14.5″ f4.5 with a Zambuto mirror, you can upgrade to a quartz mirror for even better planetary views. I’ll bet with the Zambuto quartz mirror it would give better planetary views in good seeing than the TOA 150. Deep sky objects would be no contest.

    Astro-Master: from an online thread entitled, Visual Only: 150mm Triplet APO vs 14″ Dobsonian

    I would vote the 14 as well (if it is a good mirror), but the Tak may be the nicer built scope (definitely more pricey). With the budget of the 150, you could easily get a top quality premium primary and secondary mirror set and dominate the optical performance of the 150 (16″ or 14.5″ Zambuto/Lockwood/Lightholder/etc(other good makers). with 1/30 wave antares secondary, feathertouch focuser, cooling fans, etc. etc.). With the budget of a TOA 150, you could get a TSA 120, TOA 130, or TEC 140 and a nice quality dob.

    To strictly answer your question and assuming the mirrors in the obsession are good,

    On a good night with good seeing, both scopes will perform well. Coma will dominate the edge of the field in the dob unless it is corrected with a coma corrector.The Tak will be a easier to set up. The obession will take longer to cool down (especially true if it is a 2″ thick mirror). The 14″ will need to be collimated accurately before every use (recommend a good collimator like Glatter laser and Tublug barlow attachment). Stars may appear sharper in the TOA 150 (I have never used one, but I would expect this result), but you will see a ton more stars and even fainter stuff in the 14. The 14 will also have more resolving power to split tight doubles, and the 14 will be able to handle more magnification on planets. If the seeing is not as good, the TOA may perform better on planets with a sharper image. Also the TOA should cool much faster. I would expect the image to break down faster at high magnifications with the TOA than with a well collimated and cooled 14″ dob.

    If you want to do any photography, TOA no question. For visual only, it depends on the circumstances, but I would take the 14.

    Jakecru (Nevada, USA): from an online thread entitled,Visual Only: 150mm Triplet APO vs 14″ Dobsonian

    To me a Dob and apo are complementary scopes, as each is better at different things. The Dob will go a lot deeper, and will be much better for most deep sky objects IMO. Definitely the scope of choice for globular clusters, planetary nebulae and galaxies (except perhaps Andromeda). The apo will have a wider field of view, and will be generally better for larger extended objects, and rich field observing. The apo will generally yield more aesthetically pleasing views of stars. On planets the apo will give a pleasing view unless the seeing is bad. The Dob potentially has more of an upside on planets but a lot of things have to go right for it to give nice planetary views, including good thermal control and good collimation.

    turtle86, from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

    Get the large dob + a 4 or 5″ refractor for wide field.

    AxelB( QC, Canada), from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

    Not just brighter, but far more detailed. I’ve had views of planets through large Newtonians, notably Mars and Jupiter, under exceptional seeing that can simply not be duplicated through any 150mm apochromat.

    Alan French, (Upstate New York, USA); from an online thread entitled; Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

    I think we have to be careful with generalizations when commenting on APOs vs. Reflectors.

    While I generally agree with what is being said we need to be careful to separate the subjective from the objective and also ensure we are comparing instruments of comparable quality / cost irrespective of design.

    Subjectively, yes you could say the view in an ED apo is better but objectively a 14″ will have significantly higher light grasp, resolution and contrast vs. a 6″. There is just no competition.

    On my second point….

    My 14″ has a high strehl mirror and a 19% obstruction secondary. It costed me the same as a premium 6″ APO (but still much cheaper on a $ / aperture basis). With the coma corrector the views it produces are just sublime – pinpoint stars and no coma anywhere in the fov even with my 82deg 30mm. The airy disk is so tight it is almost indistinguishable from an apo.

    In excellent seeing I can see festoons within festoons on Jupiter and swirling clouds within the GRS – views that are unmatched by any 6″ apo. I doubt even a 8-10″ apo will come close.

    But I still use my 4″ and 5″ refactors and my C9.25 more simply because they are “easier” given my limited time. The 14″ comes out on the weekends or on dark site trips. To me the refactors have a completely different value proposition.

    Astrojedi(Southern California, USA); from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

     

    I’ve previously reported running my TOA150 up against Cotts’ 12″ with Lockwood optics.

     

    On large structures – say like the Pleiades or other things bigger than a degree across and maybe the moon, the Tak wins. On everything else, the Dob wins easily.

    If you want to shoot images, the Tak wins on everything (but you don’t want to shoot images.)

    If you want to put it in your car, it’s roughly a draw – the Tak is smaller but it demands a considerable mount.

     

    If you want to draw a lineup make new friends at a star party .. the Tak will supply all weekend.

    Noisejammer (Toronto, Canada), from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

    Not unusual to get 1-2″ seeing here. I also observe from Mt Laguna ~7000ft elevation (which is about 50 minutes away) where on occasions I have experienced sub arc second seeing and Mag 6.8 skies. There with seeing better than 1″ my C8 shows an incredibly detailed Dumbbell nebula comparable with texture and detail reminiscent of my H-alpha shots of the nebula.

    Even in average seeing from my backyard the 14″ significantly outperformed a very good 6″ APO I had. I sold that APO as it was simply too cumbersome to move and mount.

    My personal experience suggests that there is simply no substitute for aperture in this hobby. But the reasons to acquire most scopes are driven more by personal preferences and not just objective performance criteria (which explains why I spend inordinate sums of money on premium refractors).

    Astrojedi (Southern California, USA); from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

    No 6″ APO can come close to what my 11″ to 18″ Zambuto and OMI Newts have done on the planets.

    CHASLX200 (Tampa, Florida, USA), from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.

    A few years back I compared my TEC 160ED to my 14″ XXg Dob/Newt, my experience was that ‘planetary included’ (I think Saturn was mostly used), as the seeing improved, the 14″ started easily / obviously pulling ahead. Is not often we get seeing good enough for that, but the difference was obvious to my eyes, and you can see which one was sold.

    Counterweight (Portland,Oregon, USA) from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.

     

    Is anyone, including the OP, truly cross-shopping these two scopes? While there are some opportunities for overlap, I will take my Obsession 15” every night, with the caveat that it takes time for the mirror to acclimate and the set up and collimating requires additional time/effort. I’m content with my 8” reflector most nights. I do like my refractor better on doubles, but the 15” and 8” will split tighter ones. Incidentally, my seeing is not great, but I have excellent transparency and minimal cloud cover most nights and my focus is typically on DSOs and there is NO CONTEST.

    Rare indeed is the night when using my 15” that I say, gee, I wish I would have brought out the 120mm—or even the 8”, which has a fantastic mirror, and curved vanes. Possibly, only when the session had to be curtailed early because clouds rolled in. With the 120mm I’m frequently saying to myself, boy, that would be better with my reflectors. The exception might be on nights when I want wide views or merely to surf the MW.

    Get a used quality big reflector and a less expensive, but still quite capable doublet refractor and never look back.

    Chesterguy (Stllwater, Oklahhoma, USA), from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.

    Hi everyone. As the thread starter I wanted to let everyone know I’ve decided to go with a big dob. I am considering the Obsession Ultra Compact 22″ with go-to, which is roughly the same cost as a TOA150 mounted on an EM400.

    jag32, from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.

     

    No we should all be using 60 mm stopped down to 40 mm. That would show that nasty ol’ bad seeing.

    I agree with you about aperture. I’ve been using EDs and apos paired with each other (such as 81 mm on 130 mm) and on larger instruments (81 and 102 on c8 and c14) and have yet to come away thinking: “Thank God I have this here four inch refractor to save the night’s planet viewing.” The aperture always wins. On SCTs I amend the concept, I think the common wisdom that one subtract the diameter of the CO to get the equivalent apo diameter is a good rule of thumb. But even so the bigger scope can deliver more color saturation and more deep sky.

    gnowellsct, from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.

     

    I happen to own a Orion Spaceprobe 3 and have owned at least one 70mm F/10 achromat.

    A 76mm x 700mm spherical mirror is 1/12 wave. There is no need for a parabola, a spherical mirror is a nearly perfect parabola. The refractor has 4 surfaces that must be precise spheres and unlike the reflector, the surfaces not only need precise spheres, they also need precise radii to work together.

    I would normally prefer a refractor over a similar sized reflector but in this case, this 76mm reflector has some real advantages both optically and mechanically. One advantage to the Newtonian is that the eyepiece is at the upper end of the telescope, this means the tripod can be lower and more stable.

    Jon Isaac (San Diego, California, USA), from an online thread entitled: 76mm reflector versus 70mm refractor.

     

    I think a 6” f/6 Newtonian with a premium mirror on a solid alt az with under 30% of CO could be one of the best “have the cake and eat it as well” secrets in amateur astronomy. Low cost, sharp views on planets that easily exceed those of a 4” apo (I also use a 4” fluorite Tak sometimes), bigger focus sweet spot and the advantage of almost fully illuminating wide field eyepieces to provide nearly 3 degrees of field.

    Ratnamaravind (San Diego, California USA), from an online thread entitled: 6″ f/6 Newt OTA for $169.15

     

    My mass-produce 16″ GSO mirror is tested at 1/14th wave p-v, and it beats the heck out of my 11″ Zambuto.

    The point is, a 12″ GSO mirror that is barely diffraction limited will still show a tremendous amount more, with more detail, than a 6″ Zambuto.

    From what I’ve been reading, GSO mirrors are not all going to be like mine by a longshot, but most of them do a pretty decent job; with just an ok mirror, I’ll take that 12″.

    Codbear (Navota, California, USA), from an onnline thread entitled: Zambuto/Royce vs Synta/GSO.

    If you are going to quote me, quote everything I wrote that is relevant: I did say this:

    “Getting the performance possible from a larger aperture is more difficult because of thermal issues and as aperture increases, seeing becomes more and more of an issue. “

    The question I was asked was to explain to [you] about why the wave front error is scaled relative to the aperture, why larger scopes have greater resolution. That’s pure optics, there are times when the seeing will support the larger optic.

    If the best you ever see is 2″ and all you observe is the planets and double stars, first, you have my sympathy.. And in that case, the 6 inch might be a good fit but as I recall, Vlad’s simulation said a larger scope was still advantageous. The actual diameter of the first minimum of the Airy disk of a 12 inch scope is twice the Rayleigh Criterion, that’s about 2.2 arc-seconds. And as experienced planetary observers like Alan French will tell you, even in poor seeing, there are moments of stable seeing where the large aperture can be used advantageously.

    In my world, 2″ is rather poor seeing for viewing the planets, being south of the jet streams close to the Pacific ocean in one of the worlds mildest climates has it’s advantages. The greater resolution and contrast possible with a 10 inch, 12 inch, 16 inch scope can be used to a good advantage.

    Last night I spent some time on the star Jabbah, with my 10 inch. It’s a pair of doubles, one is 1.3″, the other 2.2″ , both were wide clean splits, the seeing was well under 1″. The views of Jupiter and Saturn were quite nice in my 10 inch.. Viewing the planets, I generally stop at 410x, the 0.6mm exit pupil is quite dim. That’s where I stopped last night.

    I did start the scope cooling with the fan running about an hour and a half before sunset. The scope just has generic Taiwanese optics, decent optics, I’ve split doubles slightly under 0.5″, that won’t be happening in a 6 inch.

    John Isaac(San Diego, California, USA), from an online thread: Zambuto/Royce vs Synta/GSO.

     

    An instructive reminder (and very sobering for refractor nuts) of the effects of an obstruction in Newtonian(and other) telescope optics by engineer and veteran astro-imager, Thierry Legault. See here for details.

     

    Looks like you have some pretty nice gear already. Sell the DM4 and get an 8″ dob for observing.

    Keith Rivich, (Cypress, Texas, USA), from an online thread entitled: 4″ ED refractor vs 6″ f/5  for visual on a DM4?

    Both are really fine choices for grab and go and visual. I have both, and Both produce an image that is more alike than different.The refractor will be easier on cheap wide field eyepieces.The newt will give you more light to work with. I would lean toward the newt given the big price difference that you see.

    vtornado, (Northern Illinois, USA), from an online thread entitled, 4″ ED refractor vs 6″ f/5  for visual on a DM4?

    6″ F/5 wins in all areas (even FOV vs 900mm ED)

    Nicolelouda, from an online thread entitled: 4″ ED refractor vs 6″ f/5  for visual on a DM4?

    Henry from NZ, on 02 Aug 2018 – 01:49 AM, said:

    The price differential between a newt and a 4” refractor is quite large where I am, so this is in newt’s favour. I do like the ease of use of a 4” refractor. What do you think?

    Curious; I find a 6-inch f/5 Newt much easier to use than a 100-mm refractor, except for the cooldown period.

    In all likelihood, the views of planets and other bright objects would be much the same between the two instruments, but if the Newt has a really good mirror, then it would be clearly superior. Not by a huge margin, however.

    The main virtue of the 100-mm APO for me would be the significantly wider well-corrected field of view. Depending on the APO’s focal ratio, of course.

    Tony Flanders (Cambridge, MA, USA), from an online thread entitled:4″ ED refractor vs 6″ f/5  for visual on a DM4?

    I have owned a couple of 6 inch F/5’s and a couple of 4 inch ed/apo refractors. 6 inch F/5 Newtonians tend to get into SCT size central obstructions and thermal equilibrium is not a given the way it is with a refractor. I would go with the refractor because it’s more reliable, it’s provides nice views of the planets without waiting for it to cool.

    Jon Isaac (San Diego, California, USA); from an online thread entitled; 4″ ED refractor vs 6″ f/5  for visual on a DM4?

     

    The “Cheap Dobs” from the 5 and dime have gotten to be quite excellent, at least in sizes 12″ and under and I’ve seen them personally give the “premium” dobs a run for their money!!

    Barbie, from an online thread entitled: Zambuto/Royce vs Synta/GSO.

     

    6″ f/5 newt. To my eye though the 4″ ed will be sharp and high contrast, 6″ will out resolve it.

    Izar187(43 degrees North), from an online thread entitled; 4″ ED refractor vs 6″ f/5  for visual on a DM4?

     

    For what it’s worth –

    A good friend owns a “premium Dob” company – and will put whatever optics you want in your telescope. His personal rather large Dob has a primary by one of the commonly noted premium mirror makers (not Z or R). He has seen them all and can have whatever he wants – and picked what he wanted. I’ve observed with this scope – and it performs!

    He also sells Dobs with GSO mirrors – if that is what the customer wants. He has said that the recent GSO primaries he as gotten have been quite good. From my experience – this guy knows what he is talking about – and can tell a great mirror from a fair one.

    While I suppose you can get a less-than-wonderful mirror from GSO – there seems every reason to expect many current ones will be very fine. If it is ‘junk’ – return it – or have it re-figured.

    George N (Binghamton & Indian Lake, New York, USA), from an online thread entitled;  Zambuto/Royce vs Synta/GSO.

    I was observing Jupiter and Saturn at 250x with my 6″ F8 ‘Mass produced” optics Saturday night and they didn’t even break a sweat!!  I could have gone higher but didn’t have the eyepiece/barlow combination available to do so.  I’ve also had high end “hand figured” optics and mass produced optics at the same time and compared them side by side and found(after 50 years of observing and testing) that there is little to no difference between TODAY’s mass produced optics and the more expensive “hand figured” optics, other than cost and bragging rights!!  Hand figured, mass produced, if it shows me what I want to see, then I’ll buy it!!

    Barbie, from an online thread entitled: Zambuto/Royce vs Synta/GSO.

     

    ALL of these mirrors have their place, it’s not a matter of one OR the other, just like there’s more than one brand and model of car. The GSO / Synta are great for their low cost. At some point of involvement in the hobby some people want better and the market is there to answer, whether it’s a premium mirror or a Feathertouch focuser. The mass market mirrors are getting better and better, and that’s a good thing, but my experience and the experience of many others is that they’re still not equal to one made by a master craftsman and probably will never be. The difference between them is getting smaller, but it’s real. The bottom line is use and enjoy whatever you have and don’t worry about what others choose to do.

    bvillebob(Oregon, USA), from an online thread entitled, Zambuto/Royce vs Synta/GSO.

    The right answer will depend on individual preferences. For me the answer is very simple… 10”. No 6” scope, even a premium refractor will show more than a 10”. A 10” of even average quality optics will do everything better. Period.

    Astrojedi (Southern California, USA), form an online thread entitled, Zambuto/Royce vs Synta/GSO.

     

    Premium mirrors are a marketing device, people buy them for bragging rights or piece of mind, or feel they deserve such luxuries,but the views they produce are only marginally better on some objects , about the same on most objects. Other variables ,especially seeing conditions, collimation,tube currents, eyepieces, stray light, local thermal issues, secondary, exc, etc, are far more important then the alleged smoothness of the premium ,gourmet mirror.Folks that purchase such stuff, probably also buy paracors,premium hand grenade eyepieces,top shelf collimation aides,fans, etc, they usually although not necessarily are better at controlling the variables I mentioned and thus get the more from their scopes then the average mass market guy, and hence better views that they will attribute to their magic mirrors.

    tommy10  (Illinois, USA), from an online thread entitled Zambuto/Royce vs Synta/GSO.

     

    After owning 12.5 and 15 inch scopes, I appreciate my 8” dobs much more. Now that I know what to look for, I’m seeing things that I didn’t know I could when I started out with my first Orion 8” dob. The amount of detail visible in galaxies is the most surprising. As has been said here many times before, all large scopes do is magnify galaxies, they don’t increase their intrinsic brightness. So now I try to see the galaxies as simply smaller versions of what I saw in my bigger scopes, and I’m seeing things I never thought I could. I just had to change my expectations, and observing techniques. I’m getting to the point where I don’t want an F5 scope of any size, because of my aging eyes and their short depth of focus. So for me, going smaller and slower with an 8” F6, or even a 6” F8, is not only doable, but probable, maybe in the near future. When I want to do some serious observing, I break out the 8” F9. I haven’t even scratched the surface of what this scope can do.

    Galicapernistein, from an online thread entitled; Versatility of a 6″ Newt

    6″ is enough to get interesting views. M13 starts to break up. Planets start to get beef that the 4″ can’t muster. The view is wider. And the scope is portable.

    But 6″ is mainly a grab n go. If you drive way out some place dark, you will want a 10″ to enjoy the night. Even at home, the 10″ will be much better on planets.

    Stargazer193857, (Southern Idaho, USA), from an online thread entitled: Versatility of a 6″ Newt

    Long ago I had a 6″ F8 with 1/8 wave optics and it gave views comparable to my WO ZS110 refractor for planets but brighter on DSOs and not far behind my IM715D mak with a much wider FOV.

    dscarpa (San Diego, California, USA), from an online thread entitled; Versatility of a 6″ Newt

    There seem to be generalizations flying both ways and neither are fully accurate.

    The premium mirror makers are not fly-by-night operators. They are folks who have established solid reputations over the years by producing quality optics. And for many observers these mirrors are very much worth it even with a little wait time. To me for example an excellent/premium optical figure is immediately obvious but I am still very satisfied observing with other scopes. Many here are not.

    On the other hand Commercial mirrors receive more Q&A than folks here are lead to believe. Manufacturing technology and overall processes have come a long way in the past decade have improved in leaps and bounds. These days based on the sample set of very recent 20-25 Celestron and Sky-Watcher as well as GSOs that I have looked through the mirrors have been very good – almost 95%+ are diffraction limited. Most harmful issues actually arise from other factors in the scope – alignment, cooling, collimation, baffling etc. This is why differentiation for the premium mirror makers is now shifting to larger mirrors and/or faster focal ratios where the commercial operations are yet to catch up (and they may never go there).

    To me the Op’s question is a matter of personal preference as much as it is of performance.

    Astrojedi (Southern California, USA), from an online thread entitled; Zambuto/Royce vs Synta/GSO.

     

    I have been involved with manufacturing (including toys) in prc for over 2 decades, I concur with Jon’s experience. My extended family in prc are challenged daily in finding quality products and truthful information. But with wages stagnating stateside, i understand why I too have fallen for the China price.I plan to take my orion xt10g to the grave.

    waso29 (USA), from an online thread entitled: Zambuto/Royce vs Synta/GSO.

    We are definitely spoiled in this age of being able to get telescopes shipped to our doors that once upon a time were restricted to the realm of a dedicated observatory, and affordable by the masses. I’m thankful for all of it, which is a large part of why I said yes to this little guy. I don’t know how regularly it will collect photons, but it can definitely serve a good purpose.

    BlueTrane2028 (Bala Cynwyd, PA, USA), from an online thread entitled; “Junk” Orion Spaceprobe 3″

     

    I’ll take a pic eventually, but a 3″ mini-dob has been made.

    Used an 18″ length of 1″ black iron pipe, two floor flanges and a street elbow. Made a box to fit around the OTA to hold it and to bolt to one of the flanges, bolted the whole affair to a circle of wood I bought at Lowe’s.

    Black pipe is way too much money, so I’m in it a few bucks more than I had hoped to be… but the little scope has already proved itself to be decent. The mount needs a little work yet but it’s not shaky which is obviously good. Optically, it may be that my eyes are good, or it may be that I know it’s there… but I swear I could see the Cassini division (barely) and some surface banding on Saturn with a 6mm Expanse eyepiece in this thing. It’s clearly not a deep sky scope, but it’s plenty fine as a quick grab.

    I’m not sure what role it will play in my collection (since I have other quick grabs), but it’s now completely usable.

    BlueTrane2028 ( Bala Cynwyd, PA, USA), from an online thread entitled; “Junk” Orion Spaceprobe 3″

    My old 10″ f/4.7 Dob with Synta optics was there as well, now owned by a club mate. It definitely put up sharper high magnification images of Mars than the ED150 last night.

    J.R Barnett (Petaluma, California, USA); from an online thread entitled: Update on my SW ED150 order.

    I was just observing Mars,Jupiter and Saturn at 250x(I could have gone even higher but didn’t have the eyepieces/barlow combination available to do so) this evening with my Orion 6″F8 dobsonian and had some incredibly sharp and detailed views of these planets so I would say the Chinese optics are more than up to the task for serious astronomical observations where critical fine details are to be seen. The clear sky chart for my area was indicating average seeing and transparency but I easily saw the Crepe ring of Saturn with Cassini’s division sharply defined as well as multiple bands on the globe. Mars also looked good, although still not prime due the remaining dust but Syrtis Major was seen as well as the SPC. Jupiter featured numerous bands with festoons and the GRS. Also viewed Epsilon Bootis(cleanly split), Mizar/Alcor, Alberio and M29 all from heavily light polluted and haze filled skies. Not bad for an hour long session before bedtime!!

    Barbie; from an online thread entitled, Zambuto/Royce vs Synta/GSO.

     

    Yes, there is for me. Deep-sky observing really starts to come to life with a 10. And in good seeing, it outperforms the 5-6″ class ED fracs on planets. I think the 10″ dob occupies a unique niche among telescopes. Anything bigger becomes cumbersome to handle solo. Anything smaller leaves me wishing for something bigger too often.

    If I had to live with just one scope, it would be a good 10″ dob.

    Precaud (north central New Mexico, USA), from a thread entitled; Difference between 8 inch and 10 inch Dobsonians.

    You have ruled out a 12 inch Dob. Maybe you could reconsider. A 12 inch gathers more than twice the light over an 8. You will notice quite a difference in all objects with a 12–if the optics are of good quality. I own a 12.5 inch Portaball, and it performs outstandingly on planets, globulars, open clusters, double stars, and fairly well on nebula and galaxies. Why would you rule out a truss tube? You could move up to a 12 truss from an 8, with ease of hauling, set up, take down, and storage. I store my 12 inch Portaball inside of my house on my side of the closet.

    Gene T ( south Texas, USA); from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.

    I like what Karl pointed out in the previous post. There is more than the aperture gain to consider. You make no mention of how far you plan to carry this scope or how often you plan to load or unload it. All factors to consider. I had a 10″ that was admittedly an older sonotube variety and it was HEAVY and had to be split into two parts in order for me to carry it any distance. I was younger and certainly fitter at the time. I currently have an 8″ that I can carry as a complete unit and can carry it for some distance without strain because of the lighter tube, mirror and base. I might be able to do the same with a 10″ from the same manufacturer, but it would be pushing it and I’m not getting any younger.

    The point, which is often made here, is that there are always compromises. I find myself using the 8″ much more than my 15″ partly because of the ease of set up, even though the 15″ doesn’t take that long. Obviously if the night looks like it will really be great, I have plenty of time or I can travel to a dark site than it’s worth it for the greater light grasp and additional effort of the larger aperture otherwise one can find and enjoy quite a bit with 8″.

    Chesterguy, (Stillwater, Oklahoma, USA); from an online thread entitled;Difference between 8 inch and 10 inch Dobsonians.

    Same here I only own an 8 inch currently and will one day jump to a 12 inch solid tube! I think for my personal preference I would not want to setup a truss every time I had to observe. Nor would I want to spend the extra money on the truss style setup and then be forced to buy a shroud on top of that. I’m a true rookie but from what I have read a truss design up to even a 12 inch doesn’t seem to be a benefit once you consider the extra steps of setup. In top of that they don’t seem to drop weight at all compared to solid tubes as far as I have read on the specs pages of any of the scopes I’ve looked at. They will definitely be easier to store but at the cost of not wanting to deal with setup? Not worth it. Buy solid tube avoid dew issues and body heat running through the shroud. That’s what I have learned from the forums I’ve read. Obviously far more experienced people out there than me but I’ve read a lot of what experienced people have to say.

    Ken 83 (Connecticut, USA), from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.

    I’ve got an 8 solid tube and a 12.5 truss. Guess which one I use twice per year at Cherry Springs and which I use often. From 8 to 12.5 is about one magnitude, so 8 to 10, I’m thinking is about half a magnitude.

    Deep 13, from an online thread entitled: Difference between 8 inch and 10 inch Dobsonians.

    …..the move to 10″ won’t give some improvement in viewing, but it is a half step at best, and may not prove to be as satisfying as some post suggest. Sadly, this is one of those things that people usually have to see for themselves to judge if it was worth doing. From 8″ to 12″ though is a much more obvious and dramatic step that anyone will see.

    Eddgie, from an online thread entitled: Difference between 8 inch and 10 inch Dobsonians.

    I will take the OP at his word that he’s done his homework and is satisfied a 10″ scope is all the upgrade he wants to consider. My C11 was a significant and noticeable improvement in viewing over some friends’ C8s. Familiar objects were brighter and more enjoyable to look at, AND objects that were too faint to be interesting to me opened up and became targets I sought out. Very worthwhile for me. Skip forward a few years to a shoot-out between my C11 and a 10″ scope. The 10″ scope won for cool-factor and my perception that the image wasn’t degraded by the loss of 1″ aperture. I sold, with a heavy heart, my C11 and kept the 10″.

    That’s a long, round-about way of saying that for me, a 10″ scope is a worthwhile upgrade over an 8″ scope for deep sky.

    To confuse things, I am perfectly happy with my 8″ driveway scope for lunar, planetary and double stars. I never used my 10″ or 11″ scopes at home because they needed my G11 which was a pain to assemble and set-up for an hour’s viewing (I know, not a problem for our Dobsonian-owning OP). My 8″ driveway scope requires only an Orion Sirius which I leave assembled and carry out of my garage in one trip, gives satisfying resolution (560x was not empty magnification on two near-perfect nights, 240x regularly), and provides images bright enough to trigger even my lazy color receptors so Jupiter and Saturn are more than just yellow and brown. So, there’s my case for the 8″ scope, if you’re a lunar/ planetary observer.

    macdonjh, from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.

    I’ll start:

    Jupiter in my 10 inch Dob

    Main reason (which I think but could be wrong): Good seeing with steady high altitude air. Planet high in the sky (winter).

    InkDark(Quebec, Canada), from an online thread entitled; Your best view through a reflector.

     

    For planets it would be through the 18″ f/5.5 dob I built in the early 90s. Looked at Jupiter on a night of excellent seeing using a 4.8 Nagler and 2x barlow giving 1058X. Felt like I was in orbit around the planet. The details rivaled Voyager images. Never saw it that good again.

    Second was using a 14″ f/7 homebuilt dob 250 miles NW of Sydney Australia. I was touring the Small Magellanic Cloud and got stuck on the Tarantula Nebula. It was bigger and brighter than the Orion Nebula and it wasn’t even in our galaxy!! I used an OIII filter, UHC filter and no filter. It gave a very different look each way and was spectacular each way.

    Don W(Wisconsin, USA), from an online thread entitled; Your best view through a reflector.

    Best view of a planet: Jupiter at 456X due to superb seeing conditions So many details a drawing would be impossible plus albedo shadings on Ganymede

    Saturn at 1123x due to superb seeing, in which “spokes” shadings were seen on the rings, and the C ring went down almost to the disc of the planet.

    Uranus at 493x due to excellent seeing, in which a transitory white stripe was seen by a few of us.

    Best view of a galaxy: M51, wherein the dark lane in the bridge was visible, the “D” shaped bright area around the companion and 3 fingers of faint extension and a feathered spiral stucture extending from the main galaxy on the side opposite the companion. Spiral pattern and clumps in the spiral arms all visible. Superb transparency, a very dark night, and good seeing conditions all together.

    Best view of a globular cluster: M15 fully resolved to the center into tiny little pinpoints all the way across the field and even as it exited the field. Superb seeing conditions and excellent eyepiece.

    NGC104 in which the predominant color of the cluster was yellow due to the high density of red giants. Superb seeing and larger aperture (18″)

    Best view of a planetary nebula: NGC7009 (Saturn Nebula) with center oval details, outer glow and satellite “pods” visible at 493X. Excellent seeing and transparency.

    Best view of faint stars: O/A/B giant stars in NGC206 in M31–superb seeing and darkness

    Best view of a star cluster: NGC7789 on a night of superb seeing and transparency

    Best view of a nebula: M20 on a night of great darkness and transparency: the blue area completely surrounded the emission part and the center stars in the emission art formed a long “L”. Superb seeing, transparency, and darkness

    M17>M16 where nebulosity was tracked from one nebula to the other–excellent transparency and darkness

    M17 with the nebula completely filling a 42′ field and the “swan” only a portion of the visible nebula.–superb transparency, seeing, and darkness.

    NGC6888 where the large oval was filled from one end to the other with ropy tendrils and a tendril in the center made the nebula outline look like a Greek theta. Fantastic darkness and transparency.

    The Veil nebula wherein the Witches broom handle looked like a tubular-shaped filligree of silver–superb seeing and transparency.

    NGC2359 in which 4 extensions from the center bubble could be seen and thin striae of nebula covering the center bubble. Fantastic transparency.

    M27 in which ropy “berms” of nebulosity could be seen surrounding the long oval part of the nebula–excellent transparency and seeing, allowing for a high power view.

    M76, where the outer ansae joined to make it look like a 2-handled beer stein. Amazing transparency and very high power due to good seeing.

    Eta Carinae in which the homunculus in the center appeared gold in color against a rose colored outer nebula (dark skies and 18″ aperture)

    I could go on and on. Too many things to list.

    Factors of importance: Transparency, Seeing, Darkness, collimation of the optics, cooling of the optics. When they’re all good—-MAGIC!

    All views were in the 12.5″ except where noted.

    (Starman 1) Don Pensack (Los Angeles, California, USA); from an online thread entitled: Your best view through a reflector.

     

    Best planetary- Jupiter/Saturn same night in my 8″ Orion due to good seeing and slow speed of the scope

    Best DSO – Orion Nebula in my 12″ Lightbridge (with custom mirror). Could see green, blue, and alot of structure detail.

    Blakheaven( NE Oklahoma, USA), from an online thread entitled: Your best view through a reflector.

     

    Jupiter and Saturn in my 6″ F8 dobsonian.  Saw albedo features on Ganymede and 4 moons around Saturn along with Encke’s minima and the crepe ring and  many swirls and festoons in Jupiter’s belts and with detail around the GRS.  I was using 298X and could easily make out all of these features in the best seeing I’ve experienced in my locale in many years!!  Along with the seeing, I also attribute the fine optics of my Orion Skyquest XT6, of which I  have gotten an excellent sample!!

    Best DSO: Orion Nebula complex during the winter of 2017 in my 40+ year old Japanese Erfle eyepiece in the aforementioned 6″F8 dob.

    NOTE:  My optics were perfectly aligned and properly cooled which I believe to be two of the most important factors in seeing these details.

    Barbie, from an online thread entitled; Your best view through a reflector.

     

    Jupiter in John Prattes 32” at the Winter Star Party a couple of years back. Everything I hear about the steady Florida sky was true that night. At 909x, the image scale was huge and the planet rock steady against the sky. It was literally impossible to describe what I saw, an image only rivalled by spacecraft flyby. Transparency and darkness were irrelevant, it was the steady sky and large, superb Lockwood mirror that made that view possible. A view I will never ever forget.

    Every time I view an object with my 32” the first time, is basically a lifetime best view. Galaxies and Planetary Nebula in particular look incredible in the big dob. On a great night of seeing, at high power, the Homunculus at the heart of the Eta Carina Nebula looked like a Hubble image. That’s probably my favourite so far.

    I get to observe where the sky is as dark as it can get, and the transparency is generally at the top end of the scale. But the memorable sessions usually occur when the seeing conditions are very good, which is hit and miss at my dark site. I would be happy to trade a little sky darkness for regular steady seeing. That combination and large and high quality optics make for the best combination.

    Allan Wade (Newcastle, Australia); from an online thread entitled; Your best view through a reflector.

    Saturn – 8″ Discovery dob w/ plate glass mirror was left outside all night with the top capped. I woke up before dawn, then used my 4mm Radian for a 300x view.

    It was one of those very calm summer mornings where transparency wasn’t the greatest, but the air was rock-steady.

    I could have watched it for much longer, but the sun soon came up.

    Bill Schneider(Athens, Ohio, USA); from an online thread entitled; Your best view through a reflector.

    Mars in the 20″ f/5  [Obsession] in 2003. The seeing was excellent and the detail was fantastic, with both moons visible at the same time as a bonus. Once the aperture is well into the large range, there is no substitute for superb seeing.

    For DSO’s there have been so many moments that I could not pick a single target or even a single instance of a particular target. I got started on the path to the 20″ after viewing M51 through a 24″ Tectron in dark skies 20+ years ago. As good as the view was through the 24″, the eventual views through the 20″ have been sharper.

    Redbetter, (Central Valley, California, USA); from an online thread entitled; Your best view through a reflector.

    The best view ever was through someone else’s 18 inch(?) Dob of Jupiter at a star party, high up in the alps in Europe. It was one of the darkest skies available in the country where I was living, the telescope was expertly handled, and the mirrors well cooled I would imagine.

    X3782, from an online thread entitled, Your best view through a reflector.

     

    An 8 inch is a very capable scope and a can be lifetime scope for a serious observer.

    Jon Isaac, (San Diego, California, USA); from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.

     

    I have observed for ten years with an 8″ f6 dob. I do own a 12″, but the 8″ is my main scope and love it. I never stop learning about the sky with it. Maybe mine is so good because I didn´t buy it for Christmas?

    But you are right, when I show the moon, Saturn, Omega Centauri or even a bright PN to a neighbor that has never observed through a telescope, they always say: “This is very nice, but if you only had 2″ more…”

    Javier1978( Buenos Aires, Argentina), from an online thread entitled, Difference between 8 inch and 10 inch Dobsonians.

    Can’t do just one.

    Jupiter at 1100X (stacked Barlows) in the 18″ I owned at the time, late 1990s, very dark sky, excellent transparency and seeing. Jupiter full of detail, whorls, storms, bright color bands. At Blue Canyon.

    M51 a blazing blue, at the zenith, excellent transparency and seeing, 18″, late 1990s, Blue Canyon.

    Double quasar in Ursa Major, high in the sky, with my 22″. From an average sky, suddenly thee were so many stars it was hard to make out the constellations. It was February, the Double Quasar was high, found N3079 and immediately thereafter, at about 600X, the components were visible, seemingly pulsating at different rates. Great sky lasted for 20 -25 minutes. Lake Sonoma.

    Eta Carinae, at Magellan Observatory in Australia, 24″. Most unique visual object for amateur telescopes.

    Results of the spacecraft that crashed into a comet, I and two other observers saw “sparklies” for about 8 minutes after it hit (time adjusted for lightspeed). 18″.

    Shneor(Northern California, USA), from an online thread entitled; Your best view through a reflector

    Double cluster in 12” dob with 17T4 is one of my all time favorites.

    Kadmus, from an online thread entitled; Your best view through a reflector

     

    Have you ever thought about a larger Newtonian? I have seen some fabulous high magnification planet images in 14 and 16 inch Zambuto mirrored Dobsonians that track. A quality mirror and good collimation will provide dynamite planet views.

    ShaulaB(Missouri, USA), Best scope for planetary-star cluster observing.

    In my experience the best planetary scope is a premium 32″ f3.3 Dob located in the -34o latitudes of the southern hemisphere in a very dark outback location. Same as observing everything else – aperture, optics, location and careful attention to details pays off big. It is likely a similarly located, configured, and well executed Dob of larger aperture would be better.

    Star clusters? Same thing. Individual stars, nebulae, galaxies, etc? Same thing.

    It’s difficult to answer the “What’s BEST?” question when it’s unqualified.

    Your 16″ Dob should provide extremely satisfying planetary and other observing if collimated and cooled in a dark location when conditions supported good observing. Mine sure does. I’ve had owners of large and very fine Stellarvue APO refractors take a look at Jupiter and immediately decide they need a medium-large Dob for planetary.

    Havasman (Dallas, Texas, USA); from an online thread entitled: Best scope for planetary-star cluster observing.

    You can actually make a case that a really large (maybe 6″?), premium apochromatic refractor with a great eyepiece might beat what that 16″ Dobsonian will do for you. Even if the view is not necessarily better you just might find the experience more pleasurable.

    But the price would be shocking for most of us and you might find that you actually like what the 16″ Dob does either as well or better. A 6″ refractor also generally starts getting rather long and that often means less-than optimal ergonomics on some targets.

    If I had a 16″ Dobsonian and was thinking about getting better views I’d probably consider retro-fitting a GoTo system to the Dobsonian rather buying a big refractor or Mak-Cass. The tracking reduces the distraction of having to nudge the Dobsonian along and that means you will actually see a bit better.

    If your intent were to do planetary AP then I’d be looking for something like a 14″ SCT and Barlow the thing. It’s actually a great instrument for visually observing planets as well and might compete fairly well with your 16″ Dobsonian in part due to the long “natural” focal length and the relatively good ergonomics for most targets. But especially if you got a 14″ SCT with a fork mount – not fun to try to move around/set up.

    Olecuss, from an online thread entitled: Best scope for planetary/star cluster observing.

    Why doesn’t your 16″ work for planetary/globulars?

    If it’s cooled down properly, collimated, and has a good mirror, it should perform far better than literally anything else besides a bigger Dob.

    Augustus (Connecticut, USA), from an online thread entitled: Best scope for planetary/star cluster observing.

    I’ll second the pairing of a large Dob with a fast 100mm+ refractor. I keep mine on separate mounts.

    epee, from an online thread entitled; Best scope for planetary/star cluster observing.

    Assuming that his 6-inch f/6 has a first-class mirror and is well-collimated and cooled, it’s going to equal or beat any affordable refractor on the planets and on the overwhelming majority of clusters. But a good 4-inch APO would come close on those, and beat the Newt on wide-field viewing and thermal characteristics.

    Tony Flanders (Cambridge, MA, USA); from an online thread entitled; Best scope for planetary/star cluster observing.

    And while I agree that the 120mm ED is a beautiful scope, mine lasted about 4 months before I got bored with it. I would look at even bright targets with the 120mm but if those targets would fit into the field of my 12″ Dob the were always much more pleasing to me in the bigger scope.

    Eddgie; from an online thread entitled; Best scope for planetary/star cluster observing.

     

    [Snip] “You can actually make a case that a really large (maybe 6″?), premium apochromatic refractor with a great eyepiece might beat what that 16″ Dobsonian will do for you.  Even if the view is not necessarily better you just might find the experience more pleasurable.”  End Quote.

    In my opinion, nope.

    I have access to 6″ and 11″ refractors of very good quality and they do not come close to equaling or surpassing my 18″ Obsession.

    Keith Rivich(Cypress, Texas, USA); from an online thread entitled: Best scope for planetary/star cluster observing.

    To each his/her own. I spend a week to two weeks a month observing under reasonably dark skies. There’s a lot to see in a 16 inch or 22 inch scope that’s simply beyond the reach of a 6 inch. The number of objects visible is dramatically increased as it the detail visible in existing objects .

    This is not to say , there’s not room for a smaller scope but a 6 inch F/8 apo/ed would not be my choice. My 12.5 inch F/4.06 operates at a 1482 mm focal length with a Paracorr so the maximum field of view is only about 19% narrower but it shows much more and is an easy scope.

    When I go small, I want something in return, a wide field of view with a bright image to see those objects between binos and a 10 inch F/5 or a 12.5 inch F/4.

    Sure a 12.5 inch or 25 inch doesn’t show everything one might see in the photos but there is still plenty to see. It takes me about 10 minutes to setup the 16 inch when we’re camping in the motor home and it might be a week or so until it’s time to tear it down, not much trouble at all.

    Jon Isaac(San Diego, California, USA), from  an online thread entitled; Best scope for planetary/star cluster observing.

     

    My refractor story is too long for a post. Over the years I have owned a number of refractors of various apertures focal lengths and types. I like refractors but I also like reflectors and appreciate the capabilities and limitations of each.

    I like ed/apo refractors because they are the most efficient scopes in terms of performance per inch of aperture. They offer wide field views and within the limits of their aperture, they offer the most performance at high magnifications. For astronomy, they’re the ultimate grab and go telescope. The image is erect so they’re well suited for terrestrial viewing.

    But ultimately, the resolution and fine scale contrast as well as the light gathering power of a telescope is related to its aperture and so for high resolution, high contrast observing like the planets and double stars as well as going deep, I use reflectors, these days Dobsonians.

    Jon Isaac (San Diego, California, USA), from an online thread entitled: What’s your refractor story.

     

    When I considered all the different factors, especially cost, a high quality, long-focus, optimized Newtonian always came well ahead of any other option. A large, apochromatic refractor would probably be the most desirable option if money wasn’t a factor but might be ten or twenty times more expensive than a Newtonian of the same aperture optimized for planetary observing. In the course of more than 50 years as an amateur astronomer and >30-years making telescopes, I have never looked through a better planetary telescope. (with one possible exception). On nights of steady skies, it is capable of giving exceptionally sharp, high contrast images.

    David Lukehurst (Telescope Maker, Nottingham, UK), discussing a 9.5 inch f/9.8 Newtonian reflector, from an online advert; source here.

     

    A good 10″ mirror will best a top quality 6″ APO. A lot of APO folks may no[t] like it or may disagree, but I’ve seen it many times. Most reflectors are not really well collimated. Some not well at all, some just OK. They are more finicky of collimation and tend to be slapped together on site. No contest unless the seeing is really poor, or the 10 ” reflector is just bad or poorly collimated.

    Bremms (South Carolina, USA), from an online thread entitled: Refractor or Reflector for most optical resolution.

    I think db2005’s statement about obstructed optics does not apply to resolving power. As George stated, aperture diameter is the primary parameter determining resolution. An obstruction may reduce detail or contrast on an extended object like a planet or the moon, but it won’t impact actual resolution for the most part.  Some people who are hard core double star observers actually prefer a central obstruction because it will actually increase resolution when looking for the separation between the two components of a close double.  This is because the central obstruction actually puts more light in the 1st diffraction ring at the expense of light in the airy disk, so the airy disc looks smaller which helps resolving close doubles.

    fcathell (Tucson, Arizona, USA), from an online thread entitled: Refractor or Reflector for most optical resolution.

    One also needs to understand that refractors even APO have chromatic aberration that lowers resolution. The eye and brain are very good at focusing on the image in a refractor that is in focus while ignoring the out of focus image. A camera see[s] all so you have a sharp image swimming inside a blurry one. Ask any planetary imager about trying to take high resolution images of the planets with a refractor and they will tell you that you need to take Red, Green and Blue images thr[ough] filters were the focus is adjusted for each color and then combine them. If not the image is soft because the camera sees the out of focus wavelengths from the chromatic aberration of the lens. That is why modern DSLR CCD cameras have IR blocking filters built in since camera lens are not corrector for IR and if not block the CCD seeing this out of focus image.

    Aperture determines resolution, the bigger the aperture the better the resolution. The issue is that when people start comparing refractors to reflectors they aren’t taking into account the actual quality of the optics of those two exact telescopes being judged. One needs to first look at what the theoretical resolution of any optical system could be and then actually bench test that system to see how well it was made. A poorly made reflector will easily be beaten by a well made refractor but that doesn’t mean one type is better then another.

    DavidG (Hockessin, Germany), from an online thread entitled: Refractor or Reflector for most optical resolution.

    Optical resolution depends on the aperture and nothing else.  Assuming a quality made scope, the potential resolution will always be larger with a larger aperture scope.  It’s a mathematical certainty.  Seeing conditions will dictate whether or not the theoretical resolution is ever achieved (it may never be).  You do not subtract the diameter of the secondary to determine the resolution………….a larger aperture will absolutely produce a higher resolution image if the focal length is matched appropriately and the seeing conditions allow.  

    Tom Glenn, (San Diego, California, USA), from an online thread entitled: Refractor or Reflector for most optical resolution.

     

    I had a 6-inch F/12.5 Newtonian over 50 years ago that formed Spectacular planetary images. And was actually excellent on the other usual suspects. It’s hard to explain, but a slow system feels somehow more comfortable on the eyes that these fast ones can’t match. As if the eyes know the telescope isn’t fighting itself to form a good image. That might be just psychological, but I suspect there is something to it. Kingslake and Sinclair called it “ray-bending.” The less the optics have to bend the light, the easier is the design, fabrication, alignments and comfort of use.

    Tomdey (Springwater, New York, USA); from an online thread entitled, Long Slow Newtonians.

    I have owned around ten 8 f/8 Newts and all gave a great image.

    CHASLX200 (Tampa, Florida, USA), from an online tthread entitled, Long Slow Newtonians.

    I have a 6″ f/10 Newt with an Edmund Scientific premium, spherical primary mirror with a small (20mm) secondary mirror on a curved vane spider. When I do a direct comparison with my 6″ f/8 Criterion Dynascope … which is a nice scope in it’s own right … the 6″ f10 has better contrast for planetary observing and a darker sky background when observing deep-sky objects at similar magnifications

    The differences are very noticeable and somewhat surprising since the f/10 is a spherical mirror. However, the differences and capabilities of long focal ratio spherical mirrors versus the more traditional medium focal ratio parabolic mirrors is a well worn topic on CN.

    *skyguy*(Western New York, USA); from an online thread entitled; Long Slow Newtonians.

    Three of them over the years: 10″ f/9, 8″ f/9, and 16″ f/7.

    It’s nice when the entire FOV is the sweet spot.

    It’s nice when any eyepiece that finds its way into the focuser gives a great view.

    It’s nice for minimum glass planetary work.

    It’s nice when collimation is easy (getting the optics mounted inside the tube is almost enough).

    It’s nice when collimation holds all night. No excuses performance.

    Not so nice of a tube size and mount. But, I still have a soft spot in my heart for them.

    Jeff Morgan( Prescott, Arizona, USA); from an online thread entitled, Long Slow Newtonians.

    Just finished the 6″ f/8 Edmund. Mirror came off eBay and it is fantastic like all Edmund mirrors. Stars are pinpoint sharp and sky background is pitch black. Hate to say it is so refractor like. People idolize lenses but quality mirrors are every bit as good.

    Starlease (Rocky Mountains, USA); from an online thread entitled, Long Slow Newtonians.

    I ve got a 6 inch f 8 mirror I bought in the late 90s…is probably an Edmund one as well (says ES and few other things on the back).

    That thing REALLY performs. And this is only so so main mirror collimation, a slightly twitchy focuser made of plastic plumbing parts….the diagonal is just some run of the mill thing that I have no idea of the specs on but it was something cheap I also bought back then (or in other words not some fancy 1/30 wave thing). The spider is made of something like 1/8 RODS (or bigger!) rather than thin metal vanes. The secondary can’t even be adjusted. My high power eyepieces are a oooolllld University Optics 6.8 ortho and a 10 mm 3 element Vite $10 eyepiece (with a plastic lens!).

    I’ve been watching the Mars observation reports here. I’m seeing more detail than most people are reporting here (even when a fair number of them are seeing nothing more than the polar cap). Some photographs with signifcantly large scopes are about the only thing besting my observations. Even during the height of the dust storm I was getting large scale stuff (low contrast to be sure but definitely there).

    Been doing public star gazes. Random John Q publics can often even see the large scale details with the $10 Vite !

    Imagine if I did this thing up right !

    I would prefer it to be more like f10 or a bit more….its too short most of the time.

    I drool to think what a good 8 inch f9 ish could do.

    Gawd I need to finish my 10 inch f8 1/50 wave rms scope !

    Starcanoe, from an online thread entitled,Long Slow Newtonians.

    I’ve made several 6″ f/9 and f/10 scopes (and even more mirrors). They can provide incredible images if the optics are well figured. I mostly use larger scopes but occasionally pull out 6.1″ f/10 when I need a quality ‘fix’.

    Mike Spooner, from an online thread entitled,Long Slow Newtonians.

    Mike, I can fully attest to some of the most incredible planetary views and double stars with one of your 6″ f/9 mirrors in a custom made telescope. IIRC, the secondary was only .75″ and the views of Saturn were simply breathtaking. Thanks for having made some of the finest long focal length mirrors on the planet.

    Bob S.from an online thread entitled, Long Slow Newtonians.

     

    Hi Bob!

    The 6″ seems like a humble scope size but under the most stable skies it becomes apparent how limiting the atmosphere really is for high definition viewing. I’m more convinced than ever how important accurate figure is for the finest and detailed images. Those breathtaking nights are rare enough that most folks may never get to appreciate what can be achieved. Indeed, there are areas where seeing always limits even small scopes and I feel blessed to live where the veil is often lifted.

    Best,
    Mike

    Mike Spooner, from an online thread entitled, Long Slow Newtonians.

     

    Snip: Is there a best scope/mount for most of us?

    Absolutely not!

    I am a big fan of the AWB OneSky, and I do think that it is the ideal telescope for at least 10% of all beginners. But there are far too many variables for any single scope — or even a selection of 10 different scopes — to be ideal for all beginners.

    It’s pretty clear that an 8-inch f/6 Dob for $400 offers more than twice the value of the OneSky for $200. Not only is it much more capable, but it is also much easier to use. The AWB OneSky has good ergonomics, all things considered. But the simple fact is that the Dob design works better for bigger scopes than for smaller ones. Moreover, any off-the-shelf Dob will have a focuser far superior to the OneSky’s helical focuser. And you don’t need to make a light shroud for a solid-tube Dob, as any urban observer must do for the OneSky. And an 8-inch Dob is entirely self-contained, needing no supplemental support.

    The extra aperture of an 8-inch Dob is especially important for urban and suburban observers. A 130-mm scope is very capable under dark skies, but extra aperture is a big help in combating light pollution. And there’s a fairly compelling argument that 10-inch Dobs are even better than 8-inchers.

    Now some people flat-out can’t afford $400, and others cannot store or transport an 8-inch Dob. For them, a OneSky may be a reasonable compromise. But make no mistake, the OneSky has compromise written all over it.

    Many other people may be happier with a small refractor, which is compact, simple, and maintenance-free.

    Yet others really need or want Go To. Some who are eager to get started on astrophotography really require motor drive. And so on.

    Tony Flanders( Cambridge MA, USA), from an online thread entitled; Is AWB Scope the Best Entry Level Scope for Most Beginners?

    The parabolic 130mm f/5s are decent scopes, ones like the Z130 with rings and dovetail are more versatile than the AWB, imo.

    https://www.amazon.c…e/dp/B07BRLSVWM

    A 6in f/8 used newtonian ota with metal rack and pinion focuser on a dob mount should be about 150-200 usd. A more capable all around scope imo, albeit larger and heavier. At f=1200mm and f/8, relatively inexpensive plossls and a 2x or 3x barlow can provide high power magnification.

    dmgriff, from an online thread entitled; Is AWB Scope the Best Entry Level Scope for Most Beginners?

    I’m still enjoying and using mine, and I do recommend this as a good starter scope. One provision is that the purchaser will need to construct a light baffle for the open truss. I’ve had no issues with the focuser, and mine has held collimation for at least 2 years. The optics are very good, showing detailed and crisp planetary views.

    The table top mount on mine was useable, but because I have a Porta II it rides on that most of the time.

    SteveG (Seattle, Washington, USA); from an online thread entitled; Is AWB Scope the Best Entry Level Scope for Most Beginners?

    It’s not handling a “heavy” eyepiece that I found problematic, it’s getting sharp focus at high magnifications. I have owned more 130 mm F/5s than I can remember. They can be good performers at high (>200x) but generally the focuser is an issue, it contributes to scope jiggle. The plastic upper cages of the doesn’t help. Imagine an 130 mm F/5 with a really good focuser mounted on the Portamount:

    This thread is about this scope being the ideal beginners scope. For $200, it’s about as good a good scope as one can find.

    But for many beginners $450 is well within reach and an 8 inch GSO Dob not only has the benefits of the greater aperture but the mount is solid and doesn’t require a table and the focuser sets a high standard for affordable scopes.

    Bottom line: At the $200 price point, the focuser is a liability. Spend enough to buy an 8 inch with a 2 inch Crayford and you’re getting a more more capable all around scope with a nice focuser that’s a pleasure to use. It sets a high standard mechanically that $200 scopes can’t match.

    Jon Isaac (San Diego, California, USA), from an online thread entitled; Is AWB Scope the Best Entry Level Scope for Most Beginners?

     

    Hey, Guys. F/8 is NOT slow. F/8 is normal for a Newt. F/6 is fast. It wasn’t until this plywood-and-pipes-pushalong revolution came about that F/4’s were even considered as a normal telescope (other than the odd 4-1/4″ RFT). The hand-grenade eyepiece market developed only because of the big F/4’s. I have a 10″ F/6 but my 8″ F/8 gets used more.

    NinePlanets, from an online thread entitled; Long Slow Newtonians.

    In the days of home or domestic mirror making, before the far eastern products swamped the market, F6 was considered fast, F8 normal. Before the SCTs took over F10, only slow Newts were there (and achro refractors). But Moon and planets, + bright stars and objects were the usual viewing menu. However small cats give small FOV as restricted mainly to 1.25 eyepiece views. Newts can have huge focusers and eyepieces by comparison. Big fast mirrors gave the amateur views only observatories once had. But for me the appeal of long FL is using longer FL eyepieces, with longer eye relief and comfort.

    25585, from an online thread entitled; Long Slow Newtonians.

    My 6″ F8 continues to be my most used scope. If I were stranded on a desert island and could only have one scope, it would be a 6″F8 Newtonian.

    Barbie, from an online thread entitled; Long Slow Newtonians.

    Frequently the longer slower newt will have a smaller secondary.

    Planetary contrast will be improved.

    The long slow newt will have significantly less coma. More improvement.

    It will also focus sharp much easier. More improvement.

    Although a fine adjusting focuser will help this in a fast newt.

    You can get to the same magnification in both scopes.

    With a barlow(s) or ep’s with built-in barlow, you will reach equal magnification.

    Plus the barlow or ep’s with built-in barrows will clean up off axis astigmatism.

    Correcting maybe half of the fast newts inherent aberrations in the ep.

    If you use a coma corrector, and multi-element astigmatism correcting ep’s, in a fast newt, then you can get really, really close to a long slow newt, on planets.

    But the fast newts larger secondary robs some contrast.

    Many folks maintain that the multi-element ep’s that work best in fast newts, those rob some contrast too.

    The long slow newt, with modest design ep’s, delivers a great planet.

    A fast newt of the same size, at the same magnification, needs better ep’s and coma correction to even come close to equaling it. IME

    On deep sky targets, at equal aperture and magnification… they’re [e]qual.

    Izar187, from an online thread entitled; Long Slow Newtonians.

    I have the Orion StarBlast 6…

    Under darker skies, it’s great for observing deep-sky objects. Also, given a Newtonian’s total apochromaticism, it’s good for brighter objects, too.

    The Orion 120mm f/5 achromat would also be very good for deep-sky observing, but not so much for brighter objects due to the excessive false-colour produced by short achromats when viewing same. Also, there would be no need to collimate the telescope; as there would be with a Newtonian, initially, and on occasion thereafter.

    In either event, most DSOs are rather small, so plan on getting at least a 2x barlow, and perhaps even a 3x barlow. For example, I once saw the Trapezium of Orion that made my jaw drop, and with my 6″ f/5 Newtonian. I had used a 12mm 60° eyepiece with a 2.8x barlow, and for a simulated 4.3mm(174x), at the time.

    As you can see within my image, above, I quickly abandoned the original Dobson-type mount, and for a tripod-type alt-azimuth.

    SkyMuse (Mid-South, USA); from an online thread entitled; 120mm f/5 Refractor or 150mm f/5 Reflector for DSOs?

    My 120 f/5 pushed to 120X is a little soft. I don’t think I’ve seen anyone stating that their pulling apo like magnification out of it. That being said, it’s not made for higher mags. It excels at lower power. I never found myself pushing magnication in a fast instrument. I did find it cooled quicker than a 6” f/5, so it was kept and the reflector was sold. Have you considered a 8” Dob? The greater light gathering really helps with DSO’s! Fairly light and portable for what it does. Usually has a good mirror that can take some power.

    Deepwoods1  (Connecticut, USA); from an online thread entitled; 120mm f/5 Refractor or 150mm f/5 Reflector for DSOs?

    Chicken or the Egg?  The Chicken!  

    Jon Isaacs:  I worked in telescope retail in the late 1970’s – early 1980’s. At that time there were no commercially-produced F/4 Newtonians other than Edmund’s Astroscan and Coulter’s little collapsible 4-1/4″ CT-100. (You might come across the odd Cave Astrola or Telescopics Newt/Cass convertible but those were not common.) One exception: Edmund’s big red 8″ F/5 on the fork mount that showed up about 1982.)

    At that time, the best eyepieces available for these shorties were orthoscopics and the odd surplus Erfle. Meade supplied a 2″ Erfle too. There were also the Clave Plossl’s from France but they cost a lot of money to import and the best choices were the Meade R.G. Erfles and Orthos and the Brandon Orthoscopics. Even Edmund only supplied their 28mm RKE with the A-scan.

    Then along came Coulter with their big blue 13.1″ plywood push-along. I believe that was the first large-ish F/short produced in any numbers. It was about that time that Al Nagler came on the scene with his 1-1/4″ Plossls which were the first of that design affordable by the average telescope user. Then he followed up with his 13mm Nagler design. We called it the “coffee can”. Few could afford one and the kidney bean effect and its weight made it a very hard sell.

    At least that’s how my memory has it. Almost all Newtonians commercially produced at that time were F/6 – F/10. F8 was typical. Plossl’s were new and all the rage. (I still use mine, but my Meade R.G’s get the most use.  

    NinePlanets; from an online thread entitled: Long Slow Newtonians.

    I think it’s true that fast Newtonians are pretty much a modern luxury that has made large apertures portable and practical. Back in the day, a 12.5 inch F/6 was quite rare and few Scopes were larger. Today, beginners consider a 12 inch Dob as a possibility.

    But the question here is whether the Scopes came about because of availability of the Naglers or vice versa. The eyepieces did become popular with people using all types of Scopes and since the first quality truss Dobs did not appear until nearly 10 years after the introduction of the Naglers, it would seem the eyepieces enabled the development of Premium quality Dobs.

    I don’t think the Coulter crew was a big force in popularizing the Naglers. Some years ago I purchased a 13.1 inch Blue Tube and it came with or this and Kellners.

    In the last 10 years, something similar has happened. The Ethos eyepieces and the Paracorr 2 have resulted in a move to even faster Dobs . F/3 is the new F/4. The Ethos eyepieces came about as a new design and became popular with owners of all scope types but the Paracorr 2 was designed after Al looked through one of Mike Lockwoods sub F/4 mirrors and decided it deserved a better coma corrector .

    From what I know and I have seen , it has been the existence of high quality eyepieces and then the coma correctors that have made high quality, fast Newtonians possible. Obviously TeleVue has benefitted from this shift but they do OK without the Big Dob market .

    Jon Isaac( San Diego, California, USA); from an online thread entitled: Long Slow Newtonians.

    You know what? Now that my memory is jogged a bit, there were some other sawed-off Newtonians available in ~1980: Meade sold a 6″F/5 on an equatorial mount (their model 645) and there was also an outfit (Star Instruments?) in California that produced a 6″ F/4 tube assembly with Meade accoutrements. Both of these were considered to be “wide field” telescopes but, naturally, coma was terrible and there were no parracor’s around then.

    I think it was 1980 that the TV Plossls  hit the market. (Coma still sucked.)

    These fancy new hand grenade eyepieces truly do make all the difference. They DO allow F/short (under f/8) telescopes to work and big ones to be portable. Al Nagler revolutionized the telescope industry. You’re right. The egg enabled the chicken!  

    NinePlanets; from an online thread entitled: Long Slow Newtonians.

     

    I owned a Jaegers 6″ f/5 refractor. On DSO’s it was formidable.

    But the weakness was magnification. It was great – sensational – using a 35 Panoptic at 21x. But when I put in the 22 Panoptic at 34x – the color and other aberrations were very noticeable, and it only got worse from there. Could have been that particular objective – could be the breed.

    The reflector would be a more versatile performer.

    Jeff Morgan (Prescott, Arizona, USA), from an online thread entitled; 120mm f/5 Refractor or 150mm f/5 Reflector for DSOs?

     

    I agree with both Starcanoe AND Jon Isaacs.  If one has the patience, time, and mechanical ability to set up a 12″ F/5 scope, it’s definitely going to be the better instrument in terms of performance at the eyepiece.  However, it will never have the grab ‘n go feel of a 6″ F/10 instrument — which is more likely to be 6″ F/8 these days, but that would shift Jon’s position down to a 10″ F/5, and essentially the same argument.

    A 6″ F/8 or higher is a wonderful instrument.  In a dobsonian mount, they are truely grab ‘n go as anyone’s 110mm refractor, and much more wind resistant than just about any refractor, period.  The coma, tho there, is very, very small, and, I find, genuinely tolerable, unlike F/6, and especially at F/5, where, if you’re using a Newtonian and care about a flat field, you’ve got to introduce a coma corrector, with its inherent weight on the focuser, and unique configuration issue-per-eyepiece, to say nothing of the extra stress on exacting collimation one concurrently moves up to.

    For a more refractor-like viewing experience with less fuss, faster cooling, often better performance, the 6″ F/8 newt is an unsung hero in the telescope world.  Not the stunning galaxy viewer a 10″ F/5 is, for sure, but more likely to easily split tight doubles than most 10″ F/5 owners can muster.  The 10″ F/5 could produce every bit of star splitting capacity a 6″ F/8 could, theoretically, only saying that the average 10″ F/5 owner does not possess the patience, time, or mechanical prowess to make it happen, to say nothing of the extra thermal issues involved with a 10″ mirror compared to a 6″.  And the weight of a 6″ F/8 dobsonian is about the easiest “large-sized” telescope to set up a person can find, being amazingly wind resistant, but throwing up consistently good images.

    CollinofAlabama (Lubbock, Texas, USA): from an online thread entitled; Long Slow Newtonians.

    Forgot one – collimation tolerance. Not a big deal on the Faint Fuzzies, but for planetary detail and close double stars – critical.

    Longer focal ratios have a much larger “tolerance envelope” to work with than shorter focal ratios do.

    Unless the scope has very well-engineered and beefy construction, the collimation will (not may, will) shift as the scope is moved. There are many mechanical connections where positional shift flexure can manifest themselves, particularly in a truss scope. It takes a lot of attention to detail to get the sources of play under control. And then there is flexure to consider, not just tubes, but focuser boards loaded with three or four pounds of equipment.

    Of course, this can be done. My Takahashi Epsilon e-180 is f/2.8 and stays collimated for half a dozen sessions or more. And the 24″long tube weighs 28 pounds without the tube rings.

    Jeff Morgan ( Prescott, Arizona, USA); from an online thread entitled: Long Slow Newtonians.

    I don’t know about other owners of 10 inch F/5s but I regularly split doubles not possible with a perfect 6 inch . It’s not that much effort . Collimation, a good fan and stable seeing.

    As far as collimation shift: I will just say, it is possible to build a fast Dob that does not shift collimation. It might take some time running down the various gremlins…

    I often think of Jeff’s 16 inch F/7 with its 112 inch focal length amd his various attempts at making it more user friendly. I’m more than happy with a ladderless 16 inch F/4.4. Ease of use equals more frequent use..

    Jon Isaac( San Diego, California, USA); from an online thread entitled; Long Slow Newtonians.

    Agree. From my location. Antares skims along the tree tops when at the meridian. Yet I was able to split it with an Orion 10″ f/4.7 in mediocre (5-6) seeing. I couldn’t do it with my 6″ f/9 Starfire which was set up at the same time until the 10″ Newt showed me where to look. IOW I saw it easily with the 10″ f/5 Newt and with difficulty with the 6″ f/9 APO. I’m sure that if the APO were a 6″ f/8 Newt the story would be the same.

    Daquad, from an online thread entitled; Long Slow Newtonians.

    Hello hawkinsky and welcome to the forums!

    I have had a very similar 5″ f5 tabletop reflector and found it to be very useful, particularly for widefield observations of DSO’s. The view of M31/32/110 all in the field is still a favorite.

    The problems with entry level refractors usually include a poor mount/tripod combo that make them hard to use and, as above, limited capability for higher magnification.

    Neither of these scopes really needs a large eyepiece kit. The value of a 2″ focuser over a 1.25″ focuser is lost on these scopes. The higher weight of a 2″ ep will just exacerbate the shaking of the lightweight mount carrying the refractor.

    If it was my $$, I’d get the little Dob and consider adding only 2 eyepieces: an Explore Scientific 68o 24mm and either a Meade Series 5000 825.5mm or an Explore Scientific 82o 4.7mm. (Those can relatively often be found in the classifieds here and at AstroMart for significant savings.) Then find you some dark skies and that gear will give you years of high class observing.

    Havasman (Dallas, Texas, USA); form an online thread entitled; 120mm f/5 Refractor or 150mm f/5 Reflector for DSOs?

     

    ​I had the primary in my Orion XT10i tested and it is actually quite good enough. In my experience, none of the mass market secondaries are much worth a tinker’s **** and the best bang for the buck mod optically is replacing the secondary. A friend of mine replaced his 12″ Orion primary with a Zambuto and later replaced his secondary with an Antares and the verdict was that the secondary made more difference.

    Since you asked, my opinion is that of the 4 your listed, go with the Orion or Apertura. A past club president downsized to an Orion XX12g that I have observed with a few times and it is very good, completely stock and breaks down into a handy package.

    Havasman (Dallas Texas, USA), from an online thread entitled: Mass Produced Dobsonian Optics.

    I think my synta 10″ views are quite good like havasman. I’ve looked at Antares secondaries as well, just haven’t felt the need yet to make the replacement as I’ve only had it a little over 2 months.

    Jond, (Detroit USA), from an online thread entitled, Mass Produced Dobsonian Optics.

    I don’t think modern mass produced optics tend to have a massive variation these days. At the very least quality control has gotten better in the past few years. I tend to favour Synta (skywatcher) because all of their scopes (4 at this point) I have owned have performed well optically. My issues with them are the manual dob base which is awful for high powered tracking, and the cheap standard focusers. The GOTO dobs are good though.

    Smug, from an online thread entitled, Mass Produced Dobsonian Optics.

    I can’t speak for the other brands, but I purchased an Orion 12″ scope about 5 years ago. I had budgeted enough to have the mirror re-figured because I wanted it to be capable of really excellent planetary performace.

    Much to my delight, the mirror that came in the scope was far better than I had expected. I do a lot of star testing using Suiter’s methods, and here is what I found: No turned edge, no zones, and while not premium level of smoothness, still surprisingly good. A 33% obstruction test for spherical aberration was almost perfect. At 10 waves of defocus, it was almost impossible to see any size difference in the secondary shadow size and the breakout was to close on either side to be easy to see. I was very impressed with the quality and decided that there would be little practical improvement to be made by sending it to someone for re-figuring.

    Planetary views with this scope are spectacular. Side by side, my 6″ Apo really could not keep pace, and in fact, I had better Jupiter views in this scope than in my C14 (which was not a bad C14, but not of the same quality as the Orion).

    This is not a premium quality mirror, but it is quite excellent. I don’t know if this is typical or if I got lucky, but this telescope gives the best planetary views I have ever had.

    Ed Moreno(Eddgie), from an online thread entitled, Mass Produced Dobsonian Optics.

    The primary on my 10 inch Zhumell (aka Apertura) is very good as far as I can tell through a star test. I’m sending it off to Steve Swayze soon for legit testing but I think it will fair just fine. I will also be replacing my secondary with a 1/20 wave Antares, not even going to bother testing it, just replace it.

    Muddman97(NE Oklahoma, USA), from an online thread entitled, Mass Produced Dobsonian Optics.

    That pretty much sums up what I’m looking for (good assessment). Best bang for the buck – I’m not looking to spend three times the money for only a 5% improvement.

    10001110101 (SE Ohio), from an online thread entitled, Mass Produced Dobsonian Optics.

    I had the mirror from my Apertura 12AD tested when i converted it to a three strut. I was pleasantly surprised to find out it was an excellent mirror that didn’t need any work period.

    Old Rookie (North Central Ohio, USA), from an online thread entitled, Mass Produced Dobsonian Optics.

    Meade mirrors are GSO.

    You forgot SkyWatcher, which is another Synta brand.

    The focusers on the Meades, Aperturas, and Explore Scientifics are better than the Orions and Sky-Watchers, IMO.

    Smoother and more easily adjusted and easier to use.

    The mirror cells on all of the scopes are decent in 10″ and larger.

    As for movement on the axes, I favor the Explore Scientifics, since they have borrowed from high end scopes.

    And this is true whether you get a tubed or truss version.

    The Explore Scientifics also allow placement of the focuser on either side, whatever your preference.

    As far as performance, goes, all are made in a bell-shaped curve. Your odds are good to get a halfway decent mirror, but your odds are low that you will get either a complete dog or a superb mirror.

    (the best 16″ mirror I’ve ever seen was a GSO, BTW).

    Starman1( LA, USA), from an online thread entitled, Mass Produced Dobsonian Optics.

    It’s no longer the 80’s and 90’s where mass produced mirrors were hit or miss. Now days and it has been like this for the past 15 years, Synta and GSO mirrors are of good quality. They have high tech factories that can pump out consistent quality mirrors. The mirrors are fantastic optically and anyone would be proud to own one. These two companies have revolutionized amateur astronomy. Now you can buy an affordable telescope with optics you can trust.

    Are they as good as premium optics. No, but you will have to know your stuff and look hard to tell the difference. The mechanics and motions of premium scopes are larger advantages than optics verse mass produced.

    Now in our hobby we have a choice between great and excellent. Junk and risk has largely been eliminated from the market.

    dongallo (KnoxvilleTN, USA), from an online thread entitled, Mass Produced Dobsonian Optics.

    I had a Cave Astrola 10″ F8 and a GSO 10 ” F5 side by side and they both stood up well to high magnification on the planets.  No serendipity here, just extensive testing.  Perhaps your predjudice towards premium scopes has clouded your vision!!  I also had a chance to directly compare an Orion 10″ XT to a Zambuto of similar aperture and they BOTH showed the same amount of detail in Jupiter’s cloud bands at similar magnifications.  Both were properly cooled and collimated and both seemed to have good mechanical construction that didn’t interfere with high magnification planetary performance so Yes, I would say the mass produced scopes have gotten a lot better. You and others on this forum have the  attitude that a scope has to be premium to deliver outstanding image quality and that simply isn’t the case!!

    Now we can consider this horse sufficiently beaten to death!!

    Barbie, from an online thread entitled, Mass Produced Dobsonian Optics.

     

    I had an Orion XT10 in the past and a 8 inch dob now. Both provide amazing planetary views. A 10 incher is a great all around scope.

    Steve D.(Woodstock, Georgia,USA); from an online thread entitled; A 10 inch Dob- good enough?

     

    I’m personally not a fan of the typical commercial 10″ Dobsonians. The amount of aberration is just too much for me unless you plug in a coma corrector or use premium eyepieces.

    I find the 8″ Dobsonians much more pleasing due to the somewhat slower optics.

    Olecuss, from an online thread entitled; A 10 inch Dob- good enough?

    The most important factor is the seeing, the stability of the atmosphere. But in my experience , given good seeing, my 15 year old 10 inch Taiwanese Dob outperformed my 120 mm Orion ED refractor . For a 120 mm , the 120mm Eon did a very good job but the increased resolution and contrast transfer of the 10 inch was too much for it. Comparing a 5 inch reflector with a 10 inch will be even more dramatic.

    Jon Isaac(San Diego, California, USA), from an online thread entitled; A 10 inch Dob- good enough?

     

    Actual view thru an 8″ Reflector …

    https://www.youtube….h?v=ProOhknvS3o

    mvas( Eastern Ohio, USA), from an online thread entitled; A 10 inch Dob- good enough?

    Yes. A 10″ is plenty of aperture. IMO. Planets will show plenty of detail to keep you busy including the GRS, Martian polar caps and maria, Saturn and it’s rings are stunning, and much more. Your local seeing conditions will determine how much is seen on a given night.

    Get the Dob, even if it means using your 130 for a while. Spend the time training yourself to get the most from a smaller aperture. The experience will pay dividends when you get the 10″.

    Asbytec(Pampanga, Phillipines); form an online thread entitled; A 10 inch Dob- good enough?

    10 inch Dobs will be a lot heavier than a 5 inch. Negociate for an 8 sooner, + some eyepieces. An 8 inch F6 would be fine for Moon and planets. Then you can save for a 12″ wink.gif

    Actually, I tend to agree, except I’d go for an 8″ F7 as it’s much lighter and easier to set up and collimate than a 10″ F6.  A quality 8″ aperture can provide devastatingly good planetary views.  The trouble is that F7 focal ratio is not very common and would more than likely be custom.

    Jeff B, from an online thread entitled; A 10 inch Dob-good enough?

     

    Careful! You’re asking for advice from many of those who have been infected with aperture fever!

    I think the best 6″ f/8 is an 8″ f/6, and of course a 10″ has 56% more light grasp than that… and a 12″ might be enough for the fainter DSO’s….

    Actually 10″ is a very capable scope and still quite portable for the reasonably fit. A tube for a 10″ f 4.7 fits neatly across most automobile rear seats too.

    jtsenghas (Northwest Ohio, USA); from an online thread entitled; A 10 inch Dob-good enough?

    A 10-inch Dob is a great instrument, but I think the advice on seeing conditions and bringing your Dob to thermal equilibrium mentioned earlier in this thread cannot be stressed enough.

    I live in southern New England where the skies are unsteady much of the time. On those few nights a year when skies are dry, clear and steady (and the moon is not present), you can get very good planetary views with even an 8-inch Dob and a quality 6mm EP. We’re talking cloud belt swirls and transit shadows on Jupiter, an easy Cassini split on Saturn, and the polar cap and some surface features on Mars. On nights with unsteady seeing, I like to say it’s like looking through a pot of boiling water.

    You will have to determine if the added weight, collimation, and cool-down of a 10-inch is worth the effort vs. a smaller aperture given the typical seeing under your skies. If your skies are relatively dark and steady, I’m sure the views will be tremendous.

    tmichaelbanks(New England, USA); from an online thread entitled; A 10 inch Dob-good enough?

    I had my 10” Skywatcher solid tube Dob out this morning and the Orion Nebula was outstanding. So was M41 on Canis Majorum. Last week Mars showed a ton of detail at 170X.

    You’ll love the 10” Dob.

    Sandy Houtex( Houston, Texas, USA); A 10 inch Dob-good enough?

     

    When seeing is only mediocre, a 6″ does have an advantage that conditions are more stable due to the smaller “tube of light” being used. 6″ is also a decent aperture for the brighter objects.

    Still, 10″ is a lot better for resolution and light grasp when conditions permit. Oh, so many DSO can’t be appreciated until you make at least that step up.

    Aperture fever can peter out though for the work involved with managing the really big scopes, and I now some older folks step down to 8″in their later years to reduce the physical work involved with setup and teardown. For anyone reasonably fit I think 10″is just right!

    jtsenghas, (Northwest Ohio, USA); from an online thread entitled; A 10 inch Dob-good enough?

     

    I concur with most people here, 10″ is indeed a great size!

    I consider 10″ as the “compromise size” in dobs, being the perfect compromise of portability and aperture. If you go much smaller you too often feel the limits of your light gathering/resolution power (usually on DSOs), but if you go bigger transport/potability/setup start to become significant considerations. 10″ is the happy medium.

    JoeBlow(Australia); from an online thread entitled; A 10 inch Dob-good enough?

    Realistically how easy is it to track say Mars at 200x with a Dobsonian?

    Are there many people here who are able to use a Dob for planets while making planetary drawings?

    I find it very hard to make sketches of planets with my alt-az mount (Vixen Mini Porta) and slow motion controls. I would even find it harder with a Dob.**

    Magnetic Field (UK), from an online thread entitled;A 10 inch Dob-good enough?

    It depends on the scope as well as the operator. I have no trouble tracking Mars at 400x manually with my GSO 10 inch Dob.

    On the other hand, if Mars were the on the table in front me, I couldn’t make a sketch of it.

    Jon Isaac (San Diego, California, USA); from an online thread entitled; a 10 inch Dob-good enough?

    Get the 10″! It is a good aperture for all objects and is at the limit for reasonable portability.Under dark skies, it will reveal quite a bit. Prior to the dobsonian revolution a 10″ was considered a monster fantasy scope by most enthusiasts. It will not disappoint-that is until you get the strange affliction called aperture fever. That being said, a 10″ will serve you well even if you go bigger in the future and if you dodge the fever, it will provide a lifetime of satisfying viewing.I know I still use my 6″ even with a larger scope on hand.

    aat (Connecticut, USA); from an online thread entitled; a 10 inch Dob-good enough?

     

    I have now tested quite a few Chinese mirrors using Bath interferometer. About half a dozen 12″, many 8″ and two 16″. Not a single one was below 0.8 Strehl (well one 8″ was just marginal), with a few above 0.9 (including a 12″ and a 16″), one well above 0.9 and a vast majority between 0.8 and 0.85 .

    From this admittedly limited sample I’d say that whatever method Chinese are using (manual labor or CNC polisher) they very consistently turn out diffraction limited optic. At prices they sell them, I would say a small miracle actually. I have also tested a few flats, and there you actually can find a true lemon (I bought two 70mm flats and they are both bad (not catastrophic but obviously astigmatic). This is also tested properly, by interferometer (Twyman-Green). Most flats that end up in an OTA seem decent.

    What I have also found is that they consistently put best optic into best/most expensive line (BlackDiamond or whatever), and worst optic seem to be reserved for ATMing (sold as optics parts, no OTAs). So they KNOW what each optics is like, which tells us they must use reliable metric (that Zygo shown in GSO video is not a fake!).

    PS this is all relatively recent stuff, GSO/Synta made with various branding. A few years back some of the Chinese telescopes were true abominations. One 8″ f/4 set (I still have it) has nearly spherical mirror (with about one wave of astigmatism thrown in), and secondary was so bad that I think they simply used window glass, cut an ellipse and aluminized it. This is “no brand” scope with plastic focuser and a hammertone-like green tube. If you see one of those, stay well away!!!! 

    PPS I have also tested a Zambuto 8″ f/6 using Bath IF; it came out with a 0.98+ Strehl !

    But keep it in perspective. This image was done by my friend Mark with a run-of-the-mill 12″ GSO – solid but not exceptional (I think it tested about 0.87 Strehl (*)). Yes, that is detail on Ganymede !!!

    (*) just found a report on Mark’s 12″ GSO; it measured 0.86

    Attached Thumbnails

    bratislav (Melbourne, Australia); from an online thread entitled: Zambuto/Royce vs Synta/GSO.

    << This image was done by my friend Mark with a run-of-the-mill 12″ GSO – solid but not exceptional (I think it tested about 0.87 Strehl (*)). Yes, that is detail on Ganymede !!! >>

    Incredible. Very impressive indeed !

    Chucky, from an online thread entitled: Zambuto/Royce vs Synta/GSO.

     

    In my mind, the ideal planet telescope is a 10 or 12″ EQ Newt (split ring?) in a permanent location with a clear view of the south and overhead. Add a good binoviewer, pairs of long ZAOs, and an easy way to reach the EP, and I’d be all set. In reality, it would be too expensive and I have no place to set it up permanently. So-o-o-o, I’ve arranged to buy a used 8″ f/8 EQ-mounted Newt. I’ll need to have some servicing done on the mirrors. I’m thinking that within the realm of likely possibility, this may very well be my ideal set-up. Right now it has no fan and a tall R&P focuser, so I may change those things. And I’ll built a cart for the Meade RG mount. I already have a tall adjustable chair and a Denk II with pairs of TV Plossls.

    Deep 13(NE Ohio, USA), from an online thread entitled, Ideal Planet Scope

    Actually, I had had the good fortune to view through 2 separate 8-inch f/8 reflectors. Each one had optics ground and polished by the owner. Unbelievable! These guys did an amazing on their respective mirrors. Jupiter at the Mount Kobau Star Party in Aug. 1985 I will never forget!

    Neither will I forget the Oct. 1988 opposition of Mars through Lance Oklevic’s 8-inch f/8 self fabricated newtonian reflector. It was a Sat. night, I believe, and Terence Dickinson gave a Mars lecture in the auditorium at the H.R. MacMillan planetarium. Afterwards many amateurs set up their scopes on the large concrete entrance to the Gordon Southam Observatory. A member’s AP 6-inch f/8 Apo was also pointed towards Mars.

    So yes, an 8-inch f/8 can make an ideal planet killer!

    RalphMeisterTigerman, from an online thread entitled, Ideal Planet Scope

    My ideal planetary scope would be the biggest, longest newtonian I could afford – biggest aperture, smallest central obstruction.

    In practice I have a 12″ F/5 on an NEQ6 which I occasionally use for visual, it’s great but also a giant pain in the **** – the EP is 2′ above my head in most positions and I don’t like standing on wobbly ladders in the dark, and it’s a bit awkward to mount solo. Once it’s set up I prefer it to my 14″ dobsonian since I think it gives better views and the computerized mount is a million times better than tracking by hand, but the dob gets more use because it’s much less hassle.

    Smug, from an online thread entitled, Ideal Planet Scope

    I owned a Meade 12.5 inch F/6 RG for a number of years. Honestly, for large Newtonians, GEMs are a pain in the rear.

    My thinking:

    – In getting good planetary views, seeing is the number one priority. It all starts with the seeing. One wants a scope of sufficient aperture than on a good night, it is not limited by it’s aperture.

    – In terms of planetary contrast and detail, aperture is more important than focal ratio. This is particularly true for scope on a tracking mount. Pick a focal length that is ergonomically acceptable, pick the largest aperture that is affordable.

    – Important are high quality optics.

    – Thermal management is critical.

    – The mechanical structure must be stable and free from vibration.

    – A small secondary is of some consideration but a little bigger than the minimum means alignment is easier, the illuminated circle is larger and any edge issues with the secondary are of less significance.

    My solutions:

    My best views of Jupiter and Saturn were with “Junior”, my 25 inch F/5 Obsession. The seeing in the high desert where Junior lived was rarely more than average so such views were few and far between. Our home in San Diego is often blessed with very good seeing and at time excellent seeing, under an arc-second is relatively common. A scope that big is not practical. For my backyard, this is what I consider my best planetary scope.

    – 13.1 inch F/5.5 Starsplitter with a Robert Royce mirror. It is a robust scope for a 13.1 inch, it’s heavy but stable, the secondary is right at 20% and it has Feathertouch focuser. It has enough aperture for the really good nights while still being ergonomically comfortable.

    – Tracking: I parted ways with 12.5 inch Meade RG when I acquired the Starsplitter. The Starsplitter was a package deal which included a Tom O, dual axis aluminum Equatorial platform. For visual observation, I think EQ platforms are superior to GEMs. A good one is rock solid and retains the superior ergonomics of the Dobsonian. The mount is rated for a 16-18 inch and yet weighs less than 30 pounds and can be carried in one hand. Truthfully though, I actually prefer manual tracking, I like the intimacy and the issues with nudging don’t arise until well past 400x.

    My backup planetary scope is my 10 inch GSO Dob. I’ve had it for 15 years, it has good optics and it’s a quicker setup. I had an Orion 120mm Eon ED/apo for a couple of years but I found the 10 inch Dob was enough better on the planets and double stars that the Eon just sat in it’s case so I sold it. The 10 inch on the dual axis EQ platform.

    I think that matching the scope to your local conditions is important. I am about 4 miles from the Pacific Ocean and generally south of the jet streams. The flow off the ocean can mean very good seeing and so in general, I have good seeing enough of the time that I do not need to fight it because there will soon be another night.

    Jon Isaac(San Diego, California, USA); from an online thread entitled, Ideal Planet Scope

    First, I would not go with a split ring Newt for exactly the reason Jon mentioned.   If you wanted that option for tracking, just get a Go2 Dob or a tracking platform.   Split ring Newt can put eyepiece in just horrible location.  

    A 10″ f/6 sounds great, but to get the small secondary (5mm fully illuminated field) it will be no better than a 12″ f/5 with the same size fully illuminated field.  In other words, you get a scope in the 10″ f/6 that is as good for planets, but not as good for just about any other use (mirror quality being equal).   The 10″ though would be lighter and easier to manage.  I have a 12″ with a fine mirror that delivers outstanding planetary views, but it takes a hand truck to move it (though it is easier to move than my 6″ Apo on a GEM mount was by many orders of magnitude!)

    The major issue with either of these is that depending on your location, seeing may limit both of these to working at less than their full capability on both nights, and the 12″ will suffer a bit more than the 10″.

    Adding boundary layer fans will up the weight of both, but since the weight of the 12″ OTA is already pushing 50 lbs, adding fans is just that much more to handle.   The 10″ could be kept under 40 lbs with fans and will be easier to boundary layer scrub (and with with boundary layer fans, cool down is going to be far less of an issue because boundary layer scrubbing means you don’t need to cool the mirror.

    I think there would be fewer occasions where the 12″ would outperform the 10″ if you live somewhere with poor seeing, but if you live somewhere with lots of excellent seeing, 12″ will just be a better all around scope and unless the only use for the instrument is planetary, then the 12″ to me seems to be the way to go.  While the OTA will be 50 lbs, this is still manageable by many people, and if it is not manageable by you, then I would think that we would not be having this conversation.   

    A highly optimized 10″ though would probably keep up, but only at the cost of loosing some of the all around capability of the 12″.   Again, if only use is planetary, a highly optimized 10″ would be hard to beat on a night of typical seeing for many.   But only hard.  Not impossible.  

    Eddgie, from an online thread entitled; Ideal planetary Scope

    The Newtonian has some inherent advantages that make it the prime candidate for a planetary scope. It is very simple, there are only two optical surfaces. Those two components can be made essentially perfect . Large apertures are very doable so they do not suffer the limited resolution and fine scale contrast of smaller aperture scopes . Very small central obstructions are possible.

    The potential is there. As with any instrument , the challenge is in the execution and in the operation .

    Jon Isaac (San Diego, California, USA), form an online thread entitled; Ideal planetary Scope

    This is my planetary telescope.It is a Mikage 210 mm F/7.7 Newtonian on a Pentax MS-5 GEM. It gives great images of the planets through my 7mm Pentax XW EP

    Stephen Kennedy( California, USA), from an online thread entitled; Ideal planetary Scope

     

    Stephen:

    I’m glad you posted the photo of your scope. When I wrote:

    “The potential is there. As with any instrument , the challenge is in the execution and in the operation .”

    I had your scope in mind.

    Jon

    Jon Isaac(San Diego, California, USA), from an online thread entitled: Ideal planetary Scope

     

    I agree with the view that aperture is key, but the cooling is a biggie too.

    About a year ago I acquired the parts for a 8″ F7 Newtonian. The mirror is a 20mm thick quartz made by Zambuto, and the secondary is tiny. I forget the dimension, but this scope is optimized for high powers/planets.

    The first time I got a good view of Saturn with this scope I was seriously impressed. Compared to a nearby 18″ Obsession, the little 8″ was showing a much sharper and more stable view (this was after several hours in the field).

    The quartz primary is the key with this thing (well, apart from the fact that the quality is superb). This scope actually produces stable images more rapidly than my 80mm triplet refractor.

    The only thing holding this scope back is that it is only 8″.

    areyoukiddingme, from an online thread entitled; Ideal Planetary Scope

     

    My best planetary view was many years ago looking at Jupiter through someone’s 18″ Zambuto mirror dob with a Televue binoviewer. Tak LE eyepieces of unknown focal length. At the time I didn’t have a lot of experience to ask more questions or to know if the seeing was unusually good. I don’t recall the magnification, but I would now estimate 350x or higher going by memory. A lot higher than I normally use now. It was driven. Cooling fans I don’t know. It was in Joshua Tree National Park, an area not known for great seeing, but it must have been pretty good that night. That evening I went back to my own un-optimized 16″ scope and realized I had a lot to do to catch up!

    A club member has an 8″ f/8 ATM dob, and it works well. Trapezium and the E and F stars were very sharp one night with better than average seeing night here in the inland area of S. California. I think the 8″ f/8 dob would be a great scope for you.

    MikeRatcliff (California, USA); from an online thread entitled; Ideal Planetary Scope

     

    My best planetary views have been through my 20″ f/5 Obsession with a Galaxy mirror. Mars was best with the scope further south in frequent stable seeing (500 to 750x). I have had some of my best views of Jupiter and Saturn through it here, despite seeing that has not been as good for planets and has topped out around 357 to 417x on the best nights…but it is just idling because of the seeing. I would like to get the scope back south again to do some of the things I planned, like an albedo map of Ganymede.

    I made an off axis mask that gives me 8″ of unobstructed aperture in the least thermally disrupted part of the mirror, but I find the full 20″ aperture provides more detail on nights that are worth observing planets at 250x or above.

    A very large Dob in excellent seeing would be very difficult to top…particularly in the southern hemisphere with the planets high overhead.

    Redbetter(Central Valley, California); from an online thread entitled; Ideal Planetary Scope

    I have an 8″ F/8 home-made Newt (traditional Parks tube, mirror by me, smallish secondary, etc). I’ve used it a few times side-by-side with an Astro Physics 6″ F/12 triplet and an old Cave 8″ F/6. Several of us could see no difference in the views of moon and planets in the 3 scopes.

    Goerge N ( New York, USA); from an online thread entitled: Ideal Planetary Scope

     

    Late to the thread with my $0.02, but I’m with Redbetter in post #63. I typically experience exceptional seeing only a few times a year here in southern New England, but when the good skies do arrive my pedestrian XT8 provides some great planetary views: swirls in the belts and crisp transit shadows on Jupiter; clear, dark Cassini Division on Saturn, polar cap and reasonable surface markings on Mars. I suppose more powerful scope configurations would do better, but I find the old saw about “no substitute for good seeing” usually rules the night.

    tmichaelbanks; from an online thread entitled: Ideal Planetary Scope

     

    Check out this graph of Modulation transfer:  (from Suiter….)

    10 inch vs 12 inch MTF.jpg

    Now, it is for comparing a 10-inch unobstructed optic to a 12-inch 20% obstructed optic.  But the curves look exactly the same for a 5 inch unobstructed vs a 6 inch 20%. ( The cycles per arc second numbers at the bottom will have to be reduced by 1/2 as well…)  You can scale the diagram for any two apertures where one is 1.2 times bigger than the other….. (3″ vs. 3.6″, 4″ vs. 4.8″, 5″ vs 6″, 6″ vs. 7.2″, 7″ vs 8.4″, 8″ vs 9.6″…….) Scale the numbers at the bottom as well…

    What does it say?   It says that a an unobstructed scope of aperture X cannot keep up with a 20% obstructed scope of aperture 1.2X at any spatial frequency you care to name.  The bigger, obstructed scope will have better resolution and transfer more contrast to the eye.

    The ‘one-inch-bigger’ rule of thumb is not really true if the central obstruction of the larger scope is 20% or less.

    Enjoy your popcorn!

    Cotts( Madoc, Ontario, Canada): from an online thread entitled: Mak-Newt vs. Apo Refractor?

    In my own search for the “best planetary scope” I bought and sold over 100 telescopes of most every design. As I would pick a winner, I would find a new challenger and do yet another side-by-side comp. Having the scopes under identical seeing conditions and owning dual sets of Pentax SMC orthos, and now Zeiss Abbe Orthos (4-34mm) helped keep the comps as fair as possible. While I read the theoretical differences I personally prefer seeing the images.

    Many of my best views have been through Newtonians. To me the 8” Newtonian is the unsung hero of backyard astronomy. To this day my most memorable view of Mars was through a 10” Portaball. As Jon said, seeing is the key and I happened to hit a night of near perfect seeing with the Portaball. After that experience I bought a larger Portaball because I agree there is no substitute for aperture IF the optics are very good to excellent and supported by seeing. At the same time I was climbing the aperture ladder with refractors which topped out at a D&G 8” f/12 for achromats, and my current TEC200ED though I did get a chance to view through Al George’s 15” D&G along the way.

    Over the years I found I prefer refractors. Please do not read that as stating they are better because I have had simply stunning views through Newtonians, Dall-Kirkhams and Maks. But ergonomics factor into my preference too and I prefer being seated with a binoviewer to standing on a ladder. For the last two months I have been comparing the TEC to a a 1960s Cave 12 3/4” Newtonian with arguably the finest mirror Cave ever produced, and Quartz to boot. When the seeing permits, and the big Newt is cooled to near ambient it clearly beats the TEC. Deeper color saturation and finer detail on Jupiter and Saturn. But I am up a ladder three steps at zenith and have forgotten that fact once or twice….

    While aperture – with supporting seeing – wins, people who have never used big scopes do not see the downside. Big scopes are heavy, at some point exceed one-person set up, and demand correspondingly large mounts and, preferably, permanent installation.

    My most used scope this last year has been a Takahashi FC-125. Why? Superb images, easy set up, and it matches seeing consistently. At the moment I do not have a 8” Newtonian, but if I did it would be right in there too, especially one of f/7 – f/8 focal length. I am going to build an observatory this year and will permanently mount the TEC with a smaller refractor piggybacked so I can cover all seeing. And the 18” Starmaster will be the deep sky partner.

    Itha(Bend, Oregon, USA); from an online thread entitled: Ideal Planetary Scope.

    Let us consider seeing, optics, mount stability, eye relief and exit pupil, and comfort:

    (1) seeing. Seeing is too often the limiting factor. The “best” planetary scope will have an Airy disk small enough that the view is dominated by seeing. In mathematical terms, the system (optics+seeing) Airy disk FWHM (“full width at half maximum for the central peak) will be ~ < 110% of the optics Airy disk, or the Airy disk FWHM s/b about x0.45 your best-case seeing or less. Now when we talk seeing in visual terms, we talk about seeing over the time scale of the persistence of the eye, about 1/15th of a second. If the best seeing you generally encounter is about 1 arcsec, you need an Airy disk FWHM ~ lambda/D ~0.4 arcsec (8″ aperture), and so on, where lambda is the wavelength (0.55um is about right) and D is the mirror (yes, mirror!) diameter. This will set the optimum size for your optics. In general, for the vast majority of us, this would be an aperture of about 8″-16”,

    (2) the way to think about optics quality for the planets is by examining the optics system modulation transfer function, or MTF. The MTF is the Fourier transform of the optics point spread function. Graphed, the abscissa is spatial frequency (the inverse of resolution). That is, zero spatial frequency, 0 lines/mm, is a resolution of infinity while high spatial frequency represents very fine resolution. The ordinate is contrast, which is always a value of between 1 and zero. At zero spatial frequency, the contrast is unity for any optical system, so the curve starts at unity in the upper-left hand corner. At very high spatial frequency, the contrast asymptotically approaches zero. Contrast of features for extended sources such as planets (as opposed to point sources like stars) can then be determined by examining the equivalent spatial frequency for that feature.

    Now for a perfect, unobstructed Airy disk, there is a curve descending from unity at zero spatial frequency to zero as you move to the right along the abscissa. All optical systems are imperfect to some degree, however, and thus the curve for your system will lie slightly below the “perfect” MTF curve for most spatial frequencies. Now to get more quantitative: the MTF decrease for a circular central obstruction of 15% is hardly noticeable, at 20% it is noticeable but small, and decreases rapidly from there with increasing central obscuration. Few observers would notice much difference between the 15% and the 20% obscuration but, for a planet killer, that should be the limit. Note that this is slightly larger than the secondary size due to the slightly larger diameter secondary holder. For example, my 10″ f/6/6 telescope utilizes a 1.83″ minor axis (which installed at a 45 deg angle corresponds to a circular obscuration of the primary) but the secondary holder is in fact 0.193″ in diameter. Thus, my telescope meets the 20% criterion. Could I instead install the next smaller 1.52″ “standard” size secondary for even smaller obscuration? Sure, but I would be vignetting significantly at the field edge for powers lower than about x180. I also like to look at DSOs, so this is would not be a good trade for me.

    What about geometrical aberrations, such as spherical aberration and coma? These can rapidly drop the MTF curve. This is why it is important to have very good optics, and I mean a total system peak-to-valley wavefront error of less than 1/4 lambda (again, 0.55 um is a good visual wavelength average). The secondary mirror will contribute too, of course, as would any corrector plate. Note that, due to the tilt, the secondary mirror aberrations of a Newtonian can be reduced by 1/SQRT(2). To get the total system peak-to-valley wavefront error, RSS the optical component errors. For example, suppose the primary is 1/8 wave at the (HeNe laser) interferometric wavelength of 0.63um, and the secondary is similarly 1/10 wave. We then have a total peak-to-valley wavefront error of 0.63um/0.55un * [SQRT ( 1/8^2 + (1/SQRT(2) * 1/10)^2 ] = 1/7 wave. “Diffraction limited” is often considered to be 1/4 wave for the total system, so the system in this example is diffraction limited. However, 1/7 wave of aberration will drop the MTF curve noticeably, so it is not ideal. What is ideal? A total system wavefront error of better than 1/10 wave comes very close, and is probably indistinguishable from perfect. My personal 10″ Newt has a total system peak-to-valley wavefront error at 0.55 um of 1/16 wave, making the deviation due to geometrical aberrations from the diffraction-only MTF curve indiscernible. Incidentally, I am assuming you know how to properly collimate your scope.

    (3) mounts and comfort: a poor mount is a PITA, right? A good mount for planets will do the following:

    –hold the image steady at high power (x50 the aperture size in inches),

    –place the eyepiece in a comfortable viewing position,

    –not break your back to set it up,

    –for those of us who hate “nudge-nudge-nudge,” track well enough to keep the planet in the field of view, and

    –for those of us who hate ladders, not place the eyepiece position above standing.

    A GEM with a decent drive (like those equipped with Byers or Opti-Craft machining gears) can satisfy all these needs provided the telescope focal length is short enough to keep the eyepiece position at or below eye level. As luck would have it, most of us cannot reach the eyepiece at telescope focal lengths of about 65″ (GEM) or 70″ (Dobsonian). For the latter, subtract the d’Artume tracking table height, so you also end up with about 65″. Now it is very difficult to obtain and properly secure a mirror while maintaining system optical quality of 1/10 wave P-V (peak-to-valley) or better at f/ratio < f/4.5. Dividing 65″ by f/4.5 yields a maximum mirror diameter of about 14″. Happily, this happens to about match the largest telescope we can use even in “ideal” seeing conditions.

    Thus, for those who wish to manhandle a 14″ telescope (or mount it permanently), who have occasional excellent seeing at their primary observing site, pay up for excellent optics (or make your own), and who also take great care with their mirror cell and system collimation, a 14″ Dob telescope with a tracking table (d’Artume table) is about the maximum aperture for the best planetary viewing experience.

    A GEM with 2″ and above axes will also work for such a telescope but, really, it needs to be permanently mounted. I’ve found a 10″ is about the maximum one can mount on a GEM with 1.5″ axes (the maximum mount size that can be rolled and is transportable) w/o stability problems, and an electric focuser helps, too. I am easily able to roll mine out on casters from my garage to my backyard concrete patio.

    So there you have it: for those of us with pretty good but not great seeing, a high quality 10″ telescope on a GEM with rotating rings (mandatory for comfort) would be ideal. A 12.5″-to-14″ tracking Dob would be even slightly better if seeing permits.

    OK, why not a 14″ Cass or a SCT? Both have larger central obstructions that diminish MTF, and the commercially readily available SCTs rarely have good enough optics. What about a refractor? Aperture-for-aperture, a high-quality APO (almost no lateral color) refractor will be the best of all BUT the Airy disk of a 12″ scope is HALF the width of a 6″ refractor and trounces the 6″ perfect refractor MTF curve. Go larger and refractors have problems: with lateral color correction, with mechanical distortion of the heavy lens elements, and should I mention … cost?

    (4) let us not forget our eyes. For those of us who are a bit older, we’ve probably accumulated a number of floaters in our eyeball fluid over many years. The result: these can become really annoying when the system exit pupil (= focal length of eyepiece/focal ratio of telescope) decreases below about 0.5 mm. Choose your magnification accordingly. Also, good eye relief is wonderful. For these reasons, my favorite high power eyepiece for my f/6.6 telescope is the 20mm eye relief 3.5mm Pentax XW.

    Happy observing always.

    dhferguson, from an online thread entitled: Ideal Planetary Scope.

     

    I have a 10 inch F10 Newtonion that I made many years ago , I made everything myself bar the Antare’s 1 1/4 inch low profile helical focuser and 3/4 inch secondary on its curved spider (no diffraction spikes ), its a beast as the OTA is over 2500mm long and weighs 30kg + ! but I have yet to look through any telescope at this size that best’s it on the Moon and Planets !! it shows the same detail on Jupiter as our club’s C14 easily and sharper and kills a friends Meade LX200 10 inch SCT that ain’t no slouch .

    But again the Newt is a LARGE telescope ! .. Like a 10 inch F10 APO with awesome views from the top of a 5 foot set of stairs when viewing above 70* .

    Beanerds(Darwin, Australia); from an online thread entitled: 6″ Newt vs. 8″ SCT.

    I have a good 6″ F6 Newtonian and a good Celestron C8, other than general better star images and potentially wider FOV in the 6″, overall the 8″ is superior. A comparison with a good 8″ Newtonian I would expect to be a different matter.

    Peter Drew (England, UK), from an online thread entitled: 6″ Newt vs. 8″ SCT.

    I made the jump from a Orion 8″ to a Skywatcher 14″. It provided vast improvements in planets/moons, faint reflection nebula, and distant little galaxies. But mainly just increased the amount of objects I could identify…

    I was a little disappointed in the little improvement in galaxy detail. Objects like Bodes Galaxy went from a fuzzy ball in my 8″, to a fuzzy ball with a hint of arms in my 14″.

    I would say forget about the 10″, you wouldn’t notice the difference.

    The 12″ would improve Jupiter, Saturn and allow you to chase the fainter moons. If you have a very dark site, the 12″ will bring more objects into view and provide a some improvement on large galaxies.

    You can never really upgrade from an 8″, it is the perfect blend of size and power. If you want a second scope go for a wider field (nice pair of binoculars and a mount) or save up and get the biggest beast you can fit in your car.

    Luca Brasi; from an online thread entitled: Aperture Fever? 8″vs 10″ or 12″

    +1 on moving to at least a 12″ from an 8″ That’s a 125% gain or about 1/2 to 2/3rds magnitude gain.That will give you more detail on the brighter objects you can already see with the 8″ and you’ll see faint fuzzes in the 12″ that are invisible in the 8″. Lunar and planet detail / color will increase substantially as well.

    Cosmophil(So. California, USA); from an online thread entitled: Aperture Fever? 8″vs 10″ or 12″

    In all seriousness though, I think Jim Waters and Astro-Master have the right idea. I also enjoy DSOs and Lunar. While my 11″ Teeter is extremely good, and certainly shows more than my TEC180, it was my Teeter 16″ that really opened up the sky for me in a way that the other scopes couldn’t.

    As others have said though, weight and manageability become much more of a consideration at the 16″ size than say a 12″.

    And why isn’t my Teeter 16″ in my signature? I sold it! I have given my allegiance to The Dark Lord and am awaiting completion of my SpicaEye 24″. Yes, I am a zombie.

    Codbear(Novato, California, USA); from an online thread entitled: Aperture Fever? 8″vs 10″ or 12″

    The difference in views going from 8 to 12 will generate a “wow,” so will the difference in weight. A few pounds that might seem insignificant when reading about them in the catalogue become much more significant in use, so I’d wouldn’t recommend replacing the 12 with the 8 unless you find the 12 EASY to manage because telescopes seem to get much heavier to me after the new wears off. Over time, the visual WOW becomes wow, and the weight wow become WOW!

    gwlee, from an online thread entitled: Aperture Fever? 8″vs 10″ or 12″

    I think 1 object where a 10″ shines over an 8 is breaking open the larger globulars. A 10 keeps up pretty well with a 12 on globulars, but a 12 is noticeably better on everything else(except maybe the moon). Glad you mentioned Jupiter and Saturn. People tend to think that more aperture is just for fainter stuff, but that extra resolving power is very noticeable on planets. My friends 12 always showed more detail on Jupiter than my 10. Even with my 16, seeing details like spiral arms in galaxies is tough – takes dark skies and good transparency along with averted vision/dark adapted eyes. It is possible in a 12 and even a 10 under great conditions.

    spaceoddity, from an online thread entitled: Aperture Fever? 8″vs 10″ or 12″

    There was a time I owned an 8 inch and a 12.5 inch.  Then a 10 inch F/5 was offered on Astromart at a very good price and bought it . 

     

    6035960-3bears2.jpg
    Soon I parted ways with the 8 inch because I never found a reason to use the 8 inch when the 10 was around. That was more than 15:years ago.  I still have the 10 inch and the 12.5 inch. 
    I believe ergonomic differences are more important that magnitude gained.  If a scope is too big or too awkward,  it’s unlikely to get much use.
    Jon Isaac(San Diego, California, USA); from an online thread entitled: Aperture Fever? 8″vs 10″ or 12″
    Sigh, I digress and talk too much…get the largest aperture you can afford and use easily enough, I say the 12″ (over twice the surface area) is a nice almost 1 magnitude boost over the 8″. Most importantly, get it for the right reasons and enjoy whatever aperture you decide on. There are cosmic challenges to be had in every aperture.
    Asbytec (Pampanga, PI); from an online thread entitled: Aperture Fever? 8″vs 10″ or
     

    I went from 8 to 12 and it’s a big, big difference. While I got a lot of use out of my 8″, the 12″ opened up a new world of high power planetary nebulae observing, and revealing more detail and structure in galaxies.

    Crazypanda, from an online thread entitled: Aperture Fever? 8″ vs 10″ or 12″

    Going from 8 to 12 is a good jump.   My CFO reluctantly okayed my purchase of a 12 inch dob (I had an 8 inch).  She likes globs.  After seeing M13 (and other globs) in the 12 inch, she said it was a good purchase!  

    jnmastro (Minnesota, USA), from an online thread entitled; Aperture Fever? 8″ vs 10″ or 12″

    If you are looking for a dramatic improvement on most but not all objects that would be visible in both, get the 12-inch. Yes you can see a difference in the views between an 8 and a 10-inch, and yet again between a 10 and a 12-inch. It won’t be dramatic however, but the difference between an 8 and a 12-inch is much greater. You’ll get more than twice as much light gathering power, and that will improve the views of many objects you can see through an 8-inch, and show others that won’t be seen through an 8-inch. However, if you are going to transport it in a car, the truss-tube or collapsible Dob is the option you want. If you have a bigger vehicle, or do not need to transport it to use it under at least reasonably dark skies, a solid tube Dob might be a better, and a less expensive option too.

    Achernar(Alabama, USA), from an online thread entitled: Aperture Fever? 8″ vs 10″ or 12″

    Good luck with your new 12 when you get it. FWIW, I have an 8, 10 and 12.5 (plus 6, 4.5 and 66mm). The 10 gets used the most by far. While I did build all 3 to be lightweight, the 10 inch f/6.3 sits a few feet from the patio door and gets carried out most clear nights when the moon is not involved. You could always get a ten in the future too, after you have used the 8 and 12 for a while. The 10 never fails to pIease, although the 12.5 will always do a little better side by side. The 12.5 is f/5.9 and is a bit much to carry out fully assembled, so using it means taking the time to put it together, although that only takes a few minutes. Actually, I hope to keep them all for a long time…

    Don H(SW Desert, USA), from an online thread entitled: Aperture Fever? 8″ vs 10″ or 12″

    But no matter how you cut it, a good old school 8″ F/8 Newt is the best scope going. Just the 1.5″ shaft mounts from all the makers were just total garbage in my book. Slap that 8″ F/8 on a AP 1200 and you are as good as gold.

    CHASLX200( Tampa, Florida, USA), from an online thread entitled: Long Slow Newtonians

    I have the SkyWatcher 6.( f/8)…….It’s my favorite scope, and I just spent nearly a thousand bucks on a 110mm ED refactor I use less often frown.gif……….This baby’s a keeper. It has ease of use and portability written all over it, and although I can see coma in it, it’s really negligible at F/8. I see all kinds of coma in my 8” F/6, but it’s just not a big deal at F/8. The F/8 parabola throws up one nice image, and that’s a fact!

    ColinOfAlabma(Texas, USA), from an online thread entitled; Long Slow Newtonians

    I have an 8” F9 truss on a dob mount, and I have no problem tracking. I had a 10” F5.6 Discovery dob that put up great images, but in comparison to the 8”, it just couldn’t compete at high powers, so I sold it. For me, a GEM isn’t something that would be worth the trouble.

    Galicapernistein, from an online thread entitled; Long Slow Newtonians

    Yes, if planetary performance is the ultimate application of the telescope, 99.9% of CN members would not have enough money to buy an Apo that could beat a 10″ f/6 with high quality mirrors.

    What difference is the theory of the argument if you can’t actually be realized in practical application?

    My mass produced 12″ Newtonian has given me the best planetary views I have had in 30 years of observing and I have owned 6″ Astro-Physics and C14.   Now the mirrors on my sample came out of the box with a level of quality I was surprised to see, so I would not say the everyone would be fortunate enough to share this experience. 

    I have owned 5″ Apo and while it is very sharp and contrasty, at very high powers, the types you can use on nights of superb seeing, the view gets far too dim.  The colors lose saturation, and the image gets grainy due to the very small exit pupil.   People dismiss the role of luminance on the observer’s ability to resolve low contrast detail and to me, that is unfortunate.   The larger aperture produces a much brighter image (for a given power) and stimulates more cones in the observer’s eye, and this is the real key to seeing low contrast planetary detail.   You have to fire as many cones as possible. 

    Eddgie, from an online thread entitled: 5″ Apo versus Best 7″ MAK CASS

     

    Focal length does not really matter for planetary. Have an Antares 8 inch f5 with refigured mirror to 1\14 wave that beats the heck out of my old 8 inch f7 claimed 1\8 wave Optical Mechanics scope. Quality of the main mirror is everything.

    When Mars came by spring 2014 the 8 inch f5 was showing the exact same views as my recently acquired APM 6 inch f8 double. Did not keep the APM very long.

    Starlease(Rocky Mountains, USA), from an online thread entitled;Long Slow Newtonians

     

    CHASLX200, on 08 Feb 2019 – 11:18 AM, said:

    True. My best planet views came with F/5 or faster Zambuto and OMI optics in the 11 to 18″ range.

     

    And that’s my experience, too — that a well made newtonian will beat anyone’s refractor 2″ or less of aperture.  Heck, I had the same experience with far from “prime” optics.  About 13-odd years ago, a friend of mine, God rest his soul, had one of the original Orion 120mm ED scopes, the one that came with the single-speed Synta Crayford, and its image of Saturn simply couldn’t keep up with my Meade LightBridge 8″ dob (GSO).  So 4.7″ of unobstructed Chinese doublet lens couldn’t match the Taiwanese parabolic mirror’s 8″ optical capacity.  People who claim otherwise, I guess the dob owners either had particularly bad mirrors (possible) or simply didn’t know how to collimate them (likely), or the mechanicals in their scopes can’t hold collimation well (as likely).  I can’t explain refractor people with their APM’s and the like, when most reasonably well made 8″ dobs (and especially anything larger) will clean them up on the planets, or most anything else.  We’ve got a guy in town with an XT10i that has an exceptionally good mirror, keeping up with custom scopes, and that thing shows the planets, not to mention DSO’s, better than anyone’s sub observatory sized refractor.

    But it’s not just the figure of the mirror, it’s the mechanicals to maintain collimation, and the maintenance will and ability of the scope owner to keep and maintain his scope in top functioning order.  Reflectors do require all three of these things, excellent optics, good mechanicals, and will and skill of the owner.  Refractors only require good mounts – of course they require good lenses, too, but they seem to (mostly) come with pretty decent ones these days.  It’s goes without saying that achromats have other issues, but with ED scopes, it’s usually true that they function quite close to their capacity.  Given the three variables for reflectors, many out in the field are not up to par, giving people the impression of the superior refractor.

    CollinofAlabama(Lubbock, Texas, USA), from an online thread entitled: Long Slow Newtonians.

    ColinofAlabama makes some excellent points. A good Newtonian can perform as well or better than a refractor or any other type of telescope of the same aperture and since you normally get considerably more aperture with a Newtonian it is the optimal choice for a telescope. I have been using my Mikage 210 mm F/7.7 Newtonian since I purchased it in 1988 while stationed in Japan. Those of us who use Newtonians understand and accept that they require more effort than some other types of telescopes to keep them performing at their best. However, it pays of with excellent results whether it is being used for visual or astrophotography.

    Stephen Kennedy(California, USA), from an online thread entitled, Long Slow Newtonians.

    Even my mass market 12″ dob easily showed more on pretty much every target that would fit into the field than my 6″ Astro-Physics triplet would.

    I will say that if seeing perfect double star splits is high on one’s list, it is difficult to beat a large refractor, and of course you can get a slightly larger true field, but this comes at a huge costs both in terms of money and effort.  

    Here is my 6″ on a mount that I would say is a good compliment to a 6″ triplet:

     

    C8 and 152a.jpg

     

    Yeah, if you want to have your 6″ Apo be as solid at high power as a 12″ dob, you gotta put it on a hefty mount.   This mount could hold this scope reasonably still at 200x, but it was four trips out the door to get it into action.

    By comparison, my 12″ dob is kept outside in the corner of my covered patio, and goes out in one trip and I can be observing in less than 90 seconds. 

    To the OP, I would say the 14″ is going to be far more competent on a far greater range of targets.   I know this because my 12″ is far more competent on a wider range of targets than my 6″ triplet was. 

    Of course these days, I would rater use my Comet Catcher with my Mod 3 Night Vision eyepiece than most other scopes.  Way easier to move around and WOW! the stuff I can see!!!

    Eddgie, from an online thread entitled; Visual Only Triplet Apo vs 14″ Dobsonian.

    ……………………………………………………………………………………………………………………….

    Snip: Deep 13: By the forgoing logic, I should just stick with my 5″ f/12 refractor with D&G lenses. It’s a really nice DIY scope, but it’s aperture limited. I can really blow up Saturn, but it’s dim. I think 8″ (Newt) is just the right size.

    …………………………………………………………………………………………………………………………

    With the seeing, weather and temperatures in Ohio I think a 6 or 7-inch refractor would be the scope of choice on 99-percent of nights. Of course, an apo is expensive and an F15 achromat is long and unwieldy. So for ergonomic and budgetary considerations, I think an 8-inch Newtonian “optimized” for planetary observation is an excellent choice. Just don’t sell that 5” D & G!

    Bobhen, from an online thread entitled, Ideal planet scope

    Sorry, but I think I will. The justification for the 8″ f/8 is that it will replace the 5″ and the C9.25. The 5″ rides on an EQ6 that I don’t really need for anything else. I’ll get rid of the SCT first, since I’ve never really liked it. I’ll still have a TV101 if I really want a refractor view.

    Deep 13, from an online thread entitled, Ideal planet scope

    I know many astro people who have bought and sold dozens of scope and I doubt any of them see themselves as affluent. And I have run into extremely wealthy amateurs, but one need not be affluent to enjoy the hobby. A few visits to star parties will allow anyone interested the chance to look through a wide variety of scopes. And there are so many scopes today that offer high performance at very reasonable prices. To me the 8” Newtonian is the best of that group. Years back I bought a Cave 8” f/8 Model B and it was simply excellent optically. Paid something like $900 for it complete with the original mount. In many ways I wish I had never sold it!

    Itha, (Bend, Oregon, USA), from an online thread entited, Ideal planet scope

    An F/6 or longer focal ratio mirror of 8 or 10-inches aperture can be made to a very high standard of optical quality, and that matters a lot more than the focal ratio. I have seen incredible views of the planets during steady seeing through Dobs with focal ratios as low as F/4, but most telescopes where I got those memorable views were of F/6 or longer focal ratios. As long as you have high quality optics that are properly mounted, correctly collimated, and you have good seeing, hours of enjoyable observing of the planets await you.

    Acernar(Alabama, USA), from an online thread entitled Ideal planet scope

    DNA7744, on 02 Feb 2019 – 04:13 AM, said:

    Well after much lively discussion, and with consultation with my finance minister (spouse)…I have decided that the ES 12″ truss Dobson is in my future. Will be looking on CN and other dealers for a deal and hope to have finances in place within a couple of months! My 8″ Sky-Watcher will be my quick set up scope and the ES 12 will be my detail scope when good stable weather prevails! Thanks for all the comments!

    Good luck with your new 12 when you get it. FWIW, I have an 8, 10 and 12.5 (plus 6, 4.5 and 66mm). The 10 gets used the most by far. While I did build all 3 to be lightweight, the 10 inch f/6.3 sits a few feet from the patio door and gets carried out most clear nights when the moon is not involved. You could always get a ten in the future too, after you have used the 8 and 12 for a while. The 10 never fails to pIease, although the 12.5 will always do a little better side by side. The 12.5 is f/5.9 and is a bit much to carry out fully assembled, so using it means taking the time to put it together, although that only takes a few minutes. Actually, I hope to keep them all for a long time…

    Don H(SW Desert, USA) from an online thread entitled, Aperture Fever?, 8″ vs 10″ or 12″

     

    The Portaball is my all time favorite telescope. I love my refractors and the larger dobsonians that I have owned, but if I could have only one telescope the Portaball-8 would be it. I am a friend of the firm so-to-speak and have traveled with Dave Jukem to NEAF for several years displaying and evangelizing the benefits of a high quality sphere/ball telescope. I have owned every iteration of the 8″ version of the telescope.

    Peleuba(Baltimore, Maryland, USA), from an online thread entitled, Portaball Users- Sing their Praises.

    In the late 90s I read something about Portaball and asked for their brochure. At the time I was living in Long Beach, CA and for any chance at “dark skies” had to drive anywhere from two to four hours so the portability was a huge plus, as were the Zambuto optics. After a chat or two with Peter Smitka I ordered a 10″ Portaball and then waited for it to be built. From the moment I unpacked the scope and set it up for the first time I knew I had made a great decision. What a marvelous scope! My best ever view of Mars was through the 10″PB easily beating the 6″ refractor I had at the same time. I liked the scope so much I ordered a 12.5″ PB with a Roundtable tracking platform. Selling the 10″ was hard as it had been such a great scope, but the 12.5″ gave a bit better performance especially on globulars and deep sky. I still have the 12.5″ along with a Starmaster 18″, 5″ Takahashi FC-125, a unique Cave 12.75″ with Quartz primary, and TEC200ED. The PB holds its own against everything and bests them in terms of portability. Many years ago I had friends over to look at Saturn. At the time I had the 12.5″ PB, a Takahashi FS-152, a Cave 8″ F/8 and a couple of smaller APOs. One of my friends asked “If you could only have one telescope what would it be?” Without a seconds hesitation I said, “The Portaball!” That is still true today.

    Itha(Bend, Oregon, USA), from an online thread entitled, Portaball Users- Sing their Praises.

    In 1997, I made a mistake in purchasing a 20 inch Obsession classic–too much hassle in loading, setting up, and reloading in a vehicle. Peter Smitka’s concept–the largest possible telescope that was easily portable intrigued me. I sold my Obsession, and purchased a 12.5 inch Portaball. I have enjoyed it for more than 20 years. You can’t use DSC’s and you can run into balance issues with heavier eyepieces. I bought a Tom O Platform, which was designed specifically for my telescope. It worked great, but now I rarely use the Platform. Just find, and nudge to keep the object in view. The Portaball is fun, and easy to use. You can easily spin the telescope to place the eyepiece exactly where you want it. It is very easy to load and set up. I put the telescope on my front seat, secured with a seat belt. The accessories are then placed in empty spaces in the vehicle. The optics are excellent, and the 12.5 inch Portaball performs outstandingly on all objects. Planetary detail is sharp and detailed. Deep sky objects show up very well at dark sky sites. I had purchased an 18 inch Ultra Compact. My Portaball gave better planetary views than the UC, however the UC had twice the light gathering capacity and sucked in the deep sky objects much better. I don’t know of Mag 1 still exists and makes the excellent Portaball. If I were buying a new telescope, I don’t know if I wouldn’t buy a different model. However, I do not plan to buy a new telescope, and I believe my 12.5 inch, F5 Portaball is my last, and my ‘forever’ telescope.

    Gene T( South Texas, USA); from an online thread entitled, Portaball users- Sing their Praises.

    Last night we FINALLY had a nice clear night! I decided to use my daughter’s XT6. I did a quick collimation using an Orion Laser collimator deluxe (my Astrosystems barlowed laser is 2” and the XT6 has a 1.25” focuser) and double checked with a Cheshire, it was close enough. I put the scope on the porch during dinner so it cooled down for like 1.5hrs.

    First object we looked at was the moon. It was marvelous, razor sharp. I put in my ES 6.7mm 82 def eyepiece with an Orion Shorty Barlow (I have no idea where the heck I put my powermate!) and the view was still sharp at 358x. The dob motions were ok, a little jerky at this power (but better than my DSVM Mount). I didn’t miss tracking, I was fine with manually tracking. I literally stayed on the moon for an hour.

    Next was Orion, at 179x, the trapezium E and F stars were plainly visible (no averted vision needed), the stars we pin pricks! So much detail in the nebula. I also was checking out Meissa A and B (cute double). I also tried to see Sirius B, it was hard since there was a diffraction spike right where it was, I though I got a few glimpses (I kept at it for 30min). Rigel was cool too. I also checked it the cluster in the Rosette Nebula (looks good in my ES 68deg 24mm eyepiece) and Pleiades.

    These views rivaled the sharpness of my 120mm ED scope and easily is sharper than my 8inch Edge (I never get a chance to use that scope cooled down). I also discovered that I prefer the use a manual dob while sitting, no motor drives to fuss with, completely silent, much more intimate experience with the sky (my wife keeps saying it’s because I’m getting old). We use the Nexstar Evolution for outreach or when family is over, but by myself, I just want to take my time and get lost in space. I’m thinking a manual 12 inch dob (maybe 16 but 12 looks manageable) may be next on the wish list.

    Alien Ratdog (Ann Arbor, USA); from an online thread entitled, Ode to the XT6

    The only real answer to the 6″ F/8 regarding refractors is TFOV. Well, AP, of course, but I’m talking only visual. For visual astronomy, outside of a larger true field of view, refractors have so little over the 6″ F/8, it makes them hard to swallow. Now falling temperatures through the night can bedevil cooling for any mirror, making it nigh impossible to reach equilibrium, but that doesn’t happen commonly. Folks, I own four refractors, so I love them, too, but it’s always difficult to find a reason NOT to take out the 6″ F/8 vs any of my refractors. They’re simply the unsung hero of visual astronomy. If more refractor people owned them, they’d realize what Abe, the poor post-doc, has revealed to you, the telescope using public, this very March 12th, 2019. Hear ye, hear ye!

    ColinofAlabama(Lubbock, Texas, USA), Ode to the XT6.

    As a refractor weenie I must chime in. I’ve had an XT6 since 1997. Mine is a Guan Sheng scope with 19% CO, but performance sounds similar to yours. My TV85 and friend’s Tak 78 are really good small refractors and super sharp….but they lose/lost to the XT6 each and every night for astronomical targets. My friend with the Tak was so impressed with the performance of the Dob that he brought over his Tak FS102. Well, that lost too. So he brought it back several times and the result was always the same. I mean it was fairly close, a premium 4” APO is a nice scope, but fine lunar and planetary detail was easier in the 6”. And deep sky was not as close as lunar planetary. With a 7 Nagler at 171x in the Newt on M13, the eyepiece is literally filled with stars. His 102 showed 40 -60 at similar power, which surely ain’t bad, but the difference is apparent. And the Newt cost me 300 bucks! I got my TV85 a few years after the Newt…not because I thought the 85 would beat it..I knew it wouldn’t. And besides, Al Nagler told me it wouldn’t beat it the very first time I talked to him on the phone about scopes. I got the 85 for it’s versatility as a travel, solar, nature and astronomy scope. But as I’ve said for years, as a purely astronomical platform, a good 6” f/8 Dob is the best bang for the buck going. 300 bucks!

    Alnitak 22, from an online thread entitled, Ode to the XT6

     

    I had a 6″ f/8 for over ten years. Never realized how good I had it until I sold it.

    Ed D (South Florida, USA), from an online thread entitled, Ode to the XT6

    Can’t speak to the weight of the SW6 compared to the Orion XT8, but I own a GSO Zhumell 8″, and it’s a LOT heavier than the SW6. I absolutely love my Crayford dual speed, almost as much as I hated the 2″ r&p it came with. Sold it on CN Classifieds very quickly, however. I DID have to drill two small holes in the tube. The GSO dual speed Crayford’s four holes are a little farther apart left-to-right, but way too long top-to-bottom. I drilled two small holes just below the two bottom holes, and forced the screw through for the top two, which are tight but can be made to work without further drilling. I only put a plastic baggie over my secondary! But I removed my primary and then used a portivac to suck up all the metal shavings. The existing hole is more than enough for the dual speed Crayford focuser to go through, if you need that kind of infocus for a particular eyepiece. After I installed the GSO dual speed I put flocking opposite the focuser and around the primary area. I also checked the center spot (dead on, or dead on enough, awful close, and not enough off that I could easily detect it, but I used rulers and my eye, not an inferometer or anything scientific). I blackened the edges with a sharpie and measured the reflective diameter — 147.5mm for my SW6, so, really a 5.8″ objective, but close enough. Gives me a very forgiving F/R of 8.14. The SuperView 42mm provides a relatively comfortable 2º FOV, is under $75 shipped, and provides a nice 5.16mm exit pupil. That’s $420 for scope and 2″ dual speed Crayford upgrade, not bad. I ordered a $25 Orion 1 lb counterweight, cause I needed it, but again, even after flocking, you’re gonna have trouble spending more than $500 for this setup, and it’ll kick refractor derrière, pardonne-moi. And you can’t even get a 120mm achromat for this price, and even if you got one used for this price (which isn’t fair since these could be picked up used, too, of course) the mount and setup will always be about 3 times the hassle, not to mention what will happen to both scopes in any kind of wind. Dobsonians have it all over every other design in terms of wind. And I know. I live in West Texas.

    The 6″ dob is da bomb for relatively light weight, easy to use, power-packed astronomy — easy to collimate and maintain with excellent results at the eyepiece. They’re winners, and the 2″ Crayford focuser is icing on the cake for me. There is no better value in astronomy, and at F/8, you really don’t have to worry about a coma corrector. Although the entire field in NOT coma-free, it’s close enough, and noticeably better than F/6. Refractors can still produce those oh-my-god 2.5º-plus fields that aren’t possible in a 6″ F/8, but the moon? Jupiter? Most DSOs which are smaller than 2º? Refractors that can beat the very portable 6″ F/8 are mostly found in observatories.

    ColinofAlabama(Lubbock, Texas, USA), from an online thread entitled; Ode to the XT6.

    As for the ideal planetary scope, the 3 best ones I owned were a Discovery F/9 dob, the Orion 7″ Mak-Cass, and the 6″ F8 Dob. I no longer have the Discovery Dob or the 7 ” Mak but I will never part with my 6″ f/8 dob. It’s very portable, with a quick cool-down time, it’s easy to collimate and it provides sharp lunar/planetary views. I simply plunk it down in my back yard and it’s ready to go.

    Burgher, from an online thread entitled, Ideal planet scope

    RalphMeisterTigerMan, on 19 Mar 2019 – 5:08 PM, said:

    I have noticed that on the Moon and Jupiter both the contrast and resolving power is actually quite good

    That’s what you really want right there. My 10″ is an Orion but they’re equivalent in their potential for quality mirrors. I had mine tested some years ago by John Hall and he told me he could probably make the numbers better on a test report by refiguring the primary but I’d likely never see any difference. I believed him. I put a bit of $ into a new top end including 1/16th wave Astrosystems (Antares) secondary and that made an easily seen optical improvement. That scope repeatedly puts up better images than considerably larger aperture SCT’s at outreach events and star parties. A friend of mine put a Zambuto mirror in his XT12g and then replaced the secondary with an Antares. He said the optical impact of the secondary swap was far greater, not per dollar spent but in absolute terms. I’ve made many improvements to that scope but it still has the original primary. I expect to keep it around ’til the end and it will have the same primary. You can likely find someone to refigure your mirror and take your cash but if it ain’t broke…

    Havasman(Dallas, Texas, USA), from an online thread entitled, Testing SkyWatcher 10-inch Doby Primary Mirror.

    Always, always, always, get the largest aperture you can that won’t break your bank account or your back. Aperture fever isn’t just a state of mind. It matters. Just ask the folks at the European Southern Observatory (ESO), who are shelling out over a billion dollars for the new 39 meter Extremely Large Telescope (ELT). It will be the world’s largest optical scope when it sees first light in 2024. Why are they building a 39 meter scope? Because the 100 meter scope they wanted, the Overwhelmingly Large Telescope (OWL), isn’t entirely feasible yet. Yet.

    Why do I have a 12″? Because a 22″ or 24″ isn’t entirely feasible yet. Yet.

    HDavid(Pine Mountain, Georgia, USA), from an online thread entitled: Aperture Fever?, 8″ vs 10″ or 12″

    OneSky (3-11-2019)-1.jpg

     

    Meet the latest addition to our  telescope family! My OneSky arrived yesterday and I had it out under the stars as soon as it got dark. I found the built quality and optics to be excellent and the telescope is an absolute joy to use. It came almost fully assembled and took just a few minutes to complete. The collimation was pretty close out of the box and I only had to make a few minor adjustments to get it spot-on. I haven’t tried the eyepieces that it came with opting instead to use my trusty 20mm Meade RG wide field eyepiece for first-light (33x , 2 degree FOV). The moon looked fantastic showing a generous amount of detail complete with Earthshine. The Pleiades were beautiful and fit nicely within the field of view. I then swung over to Orion sweeping from Orion’s Belt down along the Sword to the Great Nebula. The Nebula showed a nice expanse and level of detail. All four members of the Trapezium were nicely split as were the 6 members of Sigma Orionis. I then swept over to Sirius and star-hopped southwards to M41 and then up the eastern side of Canis Major back up to Sirius. I then star-hopped eastwards over to M47 and 46, and continued northeast to M48. I ended my brief first light by swinging over to Mizar and Alcor, and Mizar was easily split.

    I usually star-hop using a 50mm finder, but the wide field of view of the OneSky with this particular eyepiece was sufficient to make star-hopping easy and comfortable. The motion of the OneSky was smooth and firm and it was very comfortable to move with my hands placed on the front ring and rear mirror cell. The OneSky fit very nicely on top of my standard Meade field tripod with the Peterson accessory tray as shown here. This work well while standing, but I may build a shorter tripod or table to make the telescope a little more comfortable to use while seated.

    One small note on the focuser; the OneSky uses a simple threaded helical focuser that can get a bit wobbly as it is screwed out. Some apply a layer of Teflon tape or a thick grease to help take of the slack in the threads. I was planning on using a thin layer of grease on mine; however I found a simple alternative that worked well with this eyepiece.  Briefly, I screwed the focuser almost all the way in where the motion is tight and firm and then set the rough focus by moving the eyepiece, locking it in place with the set screws, and then set the fine focus by turning the helical focuser just a tad. This made for a very solid focuser that was easy to adjust.

    I am planning on making a few simple mods including blacking the edge of the secondary and making a simple shroud to help control dew and frost, but I am delighted with the scope just as it is. This is going to make a fantastic star-hopping companion to my imaging gear. :)

    jgraham( Miami Valley, USA), from an online thread entitled; One Sky Newtonian, Astronomers without Borders

    Glad to hear your SW 10″ dob has a good primary mirror. I’ve been very impressed with them. Not so with their secondaries, though. If you know someone with a good reference flat, have them test it. All 5 of the GSO and SW 2ndaries I’ve tested have been about 1/4 wave or worse. Even the cheapest Antares would be a good upgrade.

    Precaud(New Mexico, USA), from an online thread entitled, Testing SkyWatcher 10-inch Doby Primary Mirror.

    Getting a 10” Sky-Watcher collapsible dob was one of the best moves I ever made. When I want to take pictures of the moon for friends and family it’s what I use. I feel the optics in mine should be quite good( never looking through any others) but to say that it’s been exceptional to view through last winter and fall would be an understatement. And the views now with a CC are even more magnificent. I have not nor will probably ever have optics checked though. But would probably change the secondary down the road based of more experienced dob observers conclusions.

    jond 105 (Detroit, USA), from an online thread entitled, Testing SkyWatcher 10-inch Doby Primary Mirror.

    For visual observing, focal ratio isn’t really all that important. A high-quality 300-mm f/4 Newtonian will deliver dazzling planetary views — far better than a 90-mm f/13.3 Mak-Cas, which has both slightly longer focal length and much longer focal ratio.

    Tony Flanders(Cambridge, MA, USA), from an online thread entitled, If a slow scope is for planets…

    As far as planetary viewing, it’s generally limited by the seeing. Under a stable atmosphere, it’s limited by the aperture and the optical quality. When the seeing is stable, larger reflectors provide the best planetary views, refractors are just not big enough.

    Jon Isaac(San Diego, California, USA), from an online thread entitled, If a slow scope is for planets…

    nyx, on 25 Mar 2019 – 09:53 AM, said:

    1) a 150/750 (f/5 – fast) or 2) a 150/1200 (f/8 – slower) 

     

    So, which of the two scopes is suitable for DSOs (visual only) and why?

    It’s all a matter of opinion.  In my opinion, both are suitable for visual, DSO use.

    My preference would be for the 6-inch f/8 — smaller obstruction, less serious coma, less sensitive collimation, less expensive eyepieces will perform well with it.

    But since you have the f/5, use it and enjoy it.  It’s a very capable visual, DSO telescope in it’s own right.  With the right  eyepiece, you can achieve a wider true FOV than you could with the f/8 — potentially more pleasing views of the Pleiades, M31-32-110, and other large objects.

    No telescope is ideal for everything!

    Sketcher, from an online thread entitled, If a slow scope is for planets…

     

    Your first telescope is never the wrong scope! Truth be told, all decent telescopes can be used for any kind of visual observing. Some may be tweaked a smidge toward one goal or another, but those differences are pretty small. In any case, the telescope’s optical and mechanical quality are far more important than the f/ratio or the size of the secondary mirror.

    Personally, I find f/5 to be the ideal focal ratio for deep-sky observing with a Newtonian, all other things being equal. Coma is visible but very modest, and it’s easy to achieve a 7-mm exit pupil with widely available eyepieces.

    In fact, I think that a 150-mm f/5 Newtonian with a 2-inch focuser hits a very particular sweet spot, achieving the best deep-sky views possible within its portability class. I am considering purchasing one to replace my current 130-mm f/5 Newtonian.

    I would prefer a 150-mm f/5 to a 150-mm f/8 on optical grounds alone, and the fact that the tube is much shorter is a significant side-benefit. But mind you, if somebody gave me a high-quality 150-mm f/8 Newtonian, I would be thrilled, and I would use it very happily for deep-sky observing as well as planetary observing.

    I would prefer a somewhat smaller secondary mirror. But the difference between a 63-mm secondary mirror and, say, a 45-mm secondary mirror is pretty subtle.

    In very large apertures, Newtonian owners almost always prefer faster focal ratios simply to keep the instrument more compact, and to allow them to look through the eyepiece without using a ladder.

    Tony Flanders(Cambridge, MA, USA), from an online thread entitled; If a slow scope is for planets…

     

    Finally had some steady skies, so I tested my new XT8 on some doubles in Orion. Clearly viewed all 6 stars in the trapezium. Nice view of 4 members of Sigma.

    Alnitak, Rigel, and Eta were easy and clear beautiful splits. Pretty happy with the XT8’s performance.

    Bonco2(Florida, USA), from an online thread entitled, XT8 test night

     

    I have an XT 8, great scope , easy to use , resolves Jupiter down to the white ovals, you would have to spend thousands more to get a significantly better scope, enjoy the planets this summer.
    Tommy10( Illinois, USA), from an online thread entitled, XT8 test night
    Nice! I used to have an XT10 back in the day (in the 2000, right before high school). Now my daughter’s XT6 is the scope I use the most…I routinely get the e and f stars at 92x (13mm Nagler), this scope is very comparable to my ED120, the price boggles my mind…
    Alienratdog(Ann Arbor, USA), from an online thread entitled, XT8 test night

    Good choice, after 3.x years I still think my 8″ Newtonian delivers an impressive amount of things to look at. XT8, not too expensive, not too heavy, not to long and bulky.

    The beginning of a nice journey for you.

    N3p, from an online thread entitled, XT8 test night

     

    I sold my Z10 and bought the XT8, thus I’ve been doing several tests. So far its met my expectations and is so much easier to transport. I must say tho the Z10 had equally good optics. It was just too heavy for me.

    Bonco2( Florida, USA), from an online thread entitled, XT8 test night

     

    I have OO UK 150mm F5 newt 1/10 PV it is a delightful scope and perfect for grab n go being lightweight and not too bulky, cooldown with the fan on about 15 minutes average. It depends on your idea of grab n go as well as this is different for many people. So mine goes on AYOII and a Berlebach UNI18 , all of which goes in the car neatly enough. Set up about 10 minutes then a few minutes more if using nexus or Argo.

    Lovely scope, very versatile and it replaced a 4 inch APO and have never regretted it.

    Kashmir(England, UK), from an online thread entitled: 150mmf/5 reflectors.

    I also have the Omni XLT150 and love it. Built like a tank but lightweight! Very pleasing to the eye and quite usable on Vixen’s Porta II. Easy to collimate and yes, of course there’s coma, big it sort of comes with territory… I don’t find it intrusive to the point of being a serious problem detrimental to its use. But we all differ… I bought it last Black Friday for a hair over $200! Strongly recommended.

    Belgrade(Texas, USA), from an online thread entitled: 150mmf/5 reflectors.

    I have a great 6″f5 made by a fine maker in in Minneapolis (anyone remember the name?} after college in 1957. it has had a very good mirror, reworked by Richard Wesling the famous maker in Cincinnati. It Is a superb scope and with a Parracorr shows no coma even with Televue ethos eyepieces, and is far superior to a 4.Astroblast or (and?) hey 72mm refractor from astronomic’s good as that is. The additional aperture really helps. The telescope is quite light, even with a 2 inch focuser. Highly recommended as a grab and go, if you adjust the tripod legs to a suitable height; mine is on a rolling cart for ease of getting in and out of the garage. In any event, good luck with your choice.

    Auriga(Bill Meyers), from an online thread entitled: 150mmf/5 reflectors.

    Picked up a Celestron omni XLT 6 inch F5 for $150( actually direct swap for a motorised focuser unit I was selling for that price). It came with the 1.25 inch focuser, so I replaced it and the diagonal mirror as well as installed a handle on it(much easier to carry). The coma doesn’t bother me, I do have a coma corrector, but don’t use it on this scope. Use mainly my Nagler & ethos eyepieces. Have larger scopes up to 18 inch, but like this one for the wide field views and ease and simplicity of use.As a side note, while testing it out in its new configuration, was able to spot quasar 3C 273(mag 12.9) and a 13.5 mag comparison star nearby, 2.4 billion light years with a 6 in scope, not bad.

    GusK.( New South Wales, Australia), from an online thread entitled: 150mmf/5 reflectors.

    Quote

    The large central obstruction in a 8 SCT moves energy out from the center part of the  Airy disk into the diffraction rings making them bright and larger.

    On the other hand, the larger aperture of the SCT means the Airy disk is smaller, the diffraction rings are smaller, the energy more concentrated.  In comparing a 4 inch apo to an 8 inch SCT, the first diffraction ring of the SCT fits inside the spurious disk of the 4 inch apo.

    For my money, the best double star scope depends on your seeing and climate.  It is important not to use the Dawes limit as a measure of resolution, a Dawes limit split is a very difficult split with the centers of the airy disks nearly touching.  Double the aperture, the Dawes limit split becomes much easier.  With a 4 inch, an equal magnitude 1.2 arc-second split is very difficult, with a 10 inch, it’s wide.

    Climate is important because it thermal stability is very important, is it actually possible for the scope to truly reach thermal equilibrium?

    I like Newtonians for double star work.

    Large apertures with good quality optics are affordable, active cooling is easy, central obstructions are relatively small.  I observe the planets and double stars from our home in San Diego, it’s about 4 miles from the ocean, nice light laminar flow breezes off the ocean. It’s typically south of the jet streams.  And the climate is very mild, indoor temperatures and outdoor temperatures are typically about the same.

    1 arc-second seeing is very common, half arc-second is not uncommon.  Set the Dob out, start the fan cooling and hope for good seeing.

    I like my 10 inch, it’s handy and quite capable.  The 13.1 inch F/5.5 has better optics, cools more slowly but will split tighter doubles if the seeing allows.

    Jon Isaac( San Diego, California, USA), from an online thread entitled: Best double star scope.

    aa6ww, on 25 Apr 2019 – 4:42 PM, said:

    Best Star splitter under $700, fudging the price just a little:

     

    https://www.apm-tele…ed-focuser.html

     

     

     

    Best star splitter scope under $2000:

     

    https://www.skywatch…0-apo-refractor

     

     

    Always a Refractor, Always!

     

    When  you use those two scopes, any quality eyepiece is going to give  you excellent performance. Aside from Televue and Explorer Scientific eyepieces, APM and Stellarvue also sell excellent high magnification, short FL eyepieces.

     

     

    …Ralph

     

    A couple of years ago, I was corresponding with a fellow with an 175mm Astro-Physics apo. I split some doubles he had tried without success.  My scope was a basic 10 inch Dob.

    Two factors were important, the greater aperture and the location of the scope.

    Refractors have several advantages as double star scopes but for folks like me, a Newtonian offers more performance in an affordable package.

    Right now, there are no planets well situated during most of the evening so doubles it has to be..

    Jon Isaac(San Diego, California, USA), from an online thread entitled, Best double star scope

     

    What can I say, this grab n go 130m reflector sure punches above its weight,

    ,Last night I was viewing Jupiter with the 9mm Delite + 2.5x Powermate for 180x, and well, it was a sensational view. Multiple festoons, the GRS was a rich red, the SEB was split into 3 parts, some white ovals were seen, the edges of the NEB and SEB were clearly uneven, and the Galliean Moons were all seen as different sized discs.

    Hells Kitchen( Renmark Australia), from an online thread entitled: Jupiter in the R130sF

    All other things – e.g., optical quality and cleanliness, collimation – being equal, it comes down to aperture and field of view. The dob has a larger aperture and smaller central obstruction than the SCT, corresponding to greater light-gathering power and greater resolution. I would expect better views from the dob than the SCT. How much better? Certainly noticeable as a brighter image and perhaps noticeable as greater resolution toward the center of M13.

    Of course, “all other things” are rarely equal. The difference we’re talking about could easily be overcome differences in collimation, temperature equilibration, cleanliness, or optics (e.g., is the dob’s mirror aluminized or silvered?) of the dob and the sct.

    Isfinn(Santa Fe, New Mexico, USA), from an online thread entitled; 10″ Dob vs 8″ SCT views of a Globular Cluster?

    I too certainly expect the 10″ Newt will outperform the 8″ SCT – fewer mirrors in the optical path, easier spot-on collimation, smaller CO, etc. Plus, in my experience globs are more benefited by > aperture than other objects.

    Havasman( Dallas, Texas, USA), from an online thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

    About 20 years ago I was thinking of downsizing from a 12.5″ Starliner reflector to a smaller scope because of back pain. I made aperture masks of 10″ and 8″ to see what I would like for my next scope.

    Their was a difference between the 12.5″ and the 10″, but most DSO’s still looked good in the 10″. When I went from 10″ to 8″ there was a big difference in all DSO’s. The biggest difference was on Globular Clusters, which are one of my favorite DSO’s.

    I ended up buying a Meade 10″ XL 200 that I used for 16 years till I bought a used 18″ Obsession Classic F 4.5 which is my main telescope today.

    To make a long story short, all things being equal. the 10″ should do a better job on M13, but I would bump the power up to 150x or more with a wide field eyepiece for a better comparison between the 8″ and the 10″, if the seeing will allow.

    Astro-Master, from an online thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

    The 8″ SCT will also have a much larger secondary than the 10″ Newtonian (about 35% compared to 25% in the 10% dob). The larger secondary causes additional diffraction and affects the MTF curves. This only applies to visual not imaging. A premium 10″ Newtonian will have a further smaller secondary than a 10″ mass produced dob. Usually a premium 10″/ ~F5 Newtonian will use a 1.83″ secondary for an 18% CO whereas the 10″/F5 Asian made dobs use about a 63mm secondary.

    The 10″ dob will give much better wide field low power views. You can still wind the power up with a 10″ dob by using shorter focal length eyepieces but you can’t widen the FOV and reduce the power in a SCT beyond a certain point due to the long focal length and slow F-ratio.

    While I have only ever owned newtonians and a couple of refractors over 47 years as a visual observer, I have spent a lot of time looking through colleagues SCT’s at every type of target available. Given equal aperture I am yet to come across any SCT that can come remotely close to the views through a decent well set up and tuned newtonian. Giving 2″ of aperture away is like taking a knife to a gun fight. The SCT will have a greater “depth of focus” but at F5 the depth of focus is reasonable on the Newtonian. The SCT will have a far greater tendency to “dew up” than the Newtonian. Corrector plates are renowned dew magnets.

    ausastronomer(New South Wales, Australia), from an online thread entitled; 10″ Dob vs 8″ SCT views of a Globular Cluster?

    Yes, you should see significantly more stars in the 10-inch Dob than in the 8-inch SCT if you compare the views carefully side by side.

    But this isn’t an altogether fair comparison. To take full advantage of the extra aperture of the Dob, you should increase the magnification proportionally, using 100X in the 8-incher and 125X in the 10-incher. At these fairly big exit pupils, magnification is more important than aperture in determining how many stars you can see.

    For instance, the 8-incher at 200X would resolve M13 vastly better than the 10-incher at 125X.

    Tony Flanders(Cambridge, MA, USA), from an online thread entitled; 10″ Dob vs 8″ SCT views of a Globular Cluster?

    All else being equal the 10 inch will show about a 56% brighter image. That is fairly significant. Put another way the aperture of the 8 inch lost to the 10 inch is equal to the light grasp of a 6 inch. So the light of an 8 plus a 6 would equal that of a 10..

    Darren Drake(Chicago, USA), from an online thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

    My 2080 resolves many stars in M13. My 1100 resolves even more, especially down there in the center. Your dob will at least as well as the 1100. Probably a smidgen or two better for as mentioned above, there is considerably less manipulation of the light and a smaller central obstruction.

    Migwan (Michigan, USA), form an onine thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

    Ironically, if you look at the MTF curves, high-frequency modulation actually increases with increasing central obstruction! And it is that anomalous high-freq modulation that determines limiting resolution.

    RELATED:

    Hubble planetary and star cluster imagery before the repair mission: Operations volitiously/intentionally defocused to the outer zone focus. In the presence of (the massive) spherical aberration, that gave anomalous bump in the MTF at high spatial freqs, and that allowed post-processed images of bright things (aka planets and star clusters) to give reasonably acceptable/presentable images, for that painful hiatus, during which the repair was being approved, designed and executed!

    Image-processing where (nearly all of us) use various ~digital sharpening filters~ When used in excess, these filters present telltale artifacts like that white ring around the edges of planets and moon and ~plate of spaghetti~ H-alpha solar images… where only the selected freq presents. In that sense, most experts can pretty well tell what processing we have done.

    [Most “scientific” images go entirely unprocessed. Only then, do the analysts and scientists start executing processing to extract the quantitative data… uncontaminated by prettiness. And those are the images the public rarely gets to see… because they generally aren’t pretty!    

    Attached Thumbnails

    • 91 central obstruction MTF.jpg
    • 92 central obstruction MTF.jpg

    Tom Dey( Retired Optical scientist, Springwater, New York, USA), from an online thread entitled, Secondary Mirror Obstruction?

    How much is too much depends on more than one factor, including object of observation, other optical errors present, and observer’s tolerance. The effect is transfer of energy from the central disk to the rings area, impairing image definition. But unlike aberrations, part of this transfer is followed by diminishing of the central maxima, which means that obstructed aperture can be compared with a larger aberrated one. If “c” denotes the relative size of a circular central obstruction in units of the aperture, drop in the central intensity of diffraction pattern normalized to 1 is given by (1-c^2)^2. But if we keep the flux unchanged, the drop is only 1-c^2, which means that the square of it represents the light loss due to obscuration. Still, the double square is a good approximation of the energy lost to the rings.

    The effects of CO on image quality are routinely exaggerated. Pic below shows how much the central maxima shrinks for 33% and 50% obstruction (top, OSLO output). Maxima diameter at 33% CO is about 10% smaller, while the FWHM, which matters more for the resolution limit, is about 5% smaller. So, the obstructed aperture has at least 5% higher cutoff frequency, which does not show in the MTF normalized formalism (bottom left). If we factor it in, and use the approximate contrast cutoff for bright low-contrast details (Rutten/Venrooij), we see that the dreadful 33% CO effectively reduces aperture by less than 10% here, and the wrecking 50% CO by little over 25% – much less than what the common knowledge suggests. It means that the rest of the damage from the empirical accounts comes from (a number of) other factors.

    Attached Thumbnails

    • co.png

    Vla(Vladimir Sacek), from an online thread entitled, Secondary Mirror Obstruction?

     

    Keep in mind that even a little more aperture makes up for a substantial central obstruction! That’s because the entire airy disc shrinks and brightens in proportion to aperture. All of those curves above that I and others are presenting… are normalized to unity aperture and wavelength.

    A six-inch scope with a 30% diameter obstruction resolves far better than an unobstructed five-incher. Just generate the non-normalized point-spreads and MTFs to see that in action!

    PS: This is why a (good) modest-sized Dobsonian will always blow the socks off a good smaller refractor (any smaller refractor!) for both light-gathering and resolution!

    But, gota admit… refractors make fine finder scopes on big Newtonian reflectors…

    Attached Thumbnails

    • 12 Mars showing canali and clover leaf.jpg

    Tom Dey(Retired Optical scientist, Springwater, New York, USA), from an online thread entitled, Secondary Mirror Obstruction?

    ngc7319_20, on 02 Apr 2019 – 10:54 PM, said:

    Well, this only works in a vacuum.  Under real conditions, seeing, etc.,  the 4″ refractor will reach its resolution limit much more often than the 6″ Dob.

     

    Could you show the plots?  My understanding / experience was the equivalent obstructed scope was roughly (refractor aperture) = (obstructed aperture) – (obstruction) so the equivalent to the six-inch with 30% obstruction is a four-inch refractor.  And that assumes perfect seeing.  If your six-inch always shows perfect solid Airy patterns, then great.  But if the six inch is showing an undulating mess of star light, then the four-inch scope refractor is the one to use.

    Yes, I do indeed agree that when the seeing is bad, a little refractor is worth hauling out; just leave the good scope inside for the good nights! And when the barometer drops to zero, haul out the monster scopes!

    Actually, here are the curves for 25% central obstruction at 5, 6 and 8-inch apertures. I cranked up the aperture until the obstructed scope exceeded MTF of the 5-inch at all spatial freqs. Note that the 8-inch far exceeds the 5-inch whenever the seeing is 3 arc-sec or better. Where I’m located, 1 arc-sec seeing is not unusual and half-sec is often enough to want to take advantage of. And, only aperture can avail that. And, as a bonus… way more light. Big aperture is a win-win!  

    Attached Thumbnails

    • 19 scaled 5 6 8 MTF working.jpg

    Tom Dey(Retired Optical scientist, Springwater, New York, USA), from an online thread entitled, Secondary Mirror Obstruction?

    TOMDEY, on 03 Apr 2019 – 02:01 AM, said:

    Yes, I do indeed agree that when the seeing is bad, a little refractor is worth hauling out; just leave the good scope inside for the good nights! And when the barometer drops to zero, haul out the monster scopes!

     

    Actually, here are the curves for 25% central obstruction at 5, 6 and 8-inch apertures….. Note that the 8-inch far exceeds the 5-inch whenever the seeing is 3 arc-sec or better.

    Perfect!  Thanks for plots!  Yes that’s consistent with what I expected.  An eight-inch with 25% obstruction would be roughly equivalent to a 6-inch refractor. So of course it will beat a five-inch refractor as you say.

    NGC 7319_20(Maryland, USA), from an online thread entitled, Secondary Mirror Obstruction?

    Maybe you can build a 3″ reflector and demonstrate equality to the 3″ refractor?

    One would only need to build a reflector under 6 inches and demonstrate it’s equality (superiority) to the 3 inch refractor.

    That does not seem like much of a challenge..

    Jon Isaac(San Diego, California, USA), from an online thread entitled, ALPO Venus section telescope recommendation: it hurts.

     

    This myth and lore of refractor aperture equals 2 times reflector aperture gets me going.

    If there were a “junk status” like what we often see for credit ratings or bonds on the global financial market the ALPO Venus guideline would qualify for it.

    Btw: I was so impressed by this fellas Venus drawings (post #85):

    https://www.cloudyni…ochromat/page-4

    One of the best Venus drawings I have ever seen (unbelievable what a 40cm Dall-Kirkham can deliver)

    So I started searching the internet for similar drawings and came across that nonsense ALPO Venus watch programe section guideline. You would think ALPO (Association of Lunar and Planetary Observers) is a respectable organisation of enthusiasts.

    Magnetic Field(UK), from an online thread entitled,  ALPO Venus section telescope recommendation: it hurts.

    I had an MN56 for a brief while. It was easily better for viewing pretty much anything ex[c]e[p]t very large targets than any 80mm refractor I have ever owned.

    Some people simply don’t upgrade their web pages. As a matter of fact, I still sometimes get questions from friends about the Mars close approach that occurred a decade ago. Articles saying it is coming are still out there on the web.

    It is just the nature of the beast. Some huge quantity of data on the web is out of date.

    Eddgie, from an online thread entitled,  ALPO Venus section telescope recommendation: it hurts.

     

      I have a 10″ f/4.7 dob and an 8″ SCT (f/10 or with a reducer, f/6.3, both collimated. The views in the dob are clearly brighter and with more detail, I prefer them any time. I use the SCT for EAA only these days.

      RazvanUnderStars(Toronto, Canada), from an online thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

       

      I went from a 10″ Skywatcher to a 15″ Obsession and have been very happy with the noticeable benefits on DSOs such as planetary nebs, reflection/emission nebs, galaxies and in particular globs are quite dramatically enhanced. I saw strong green in Orion in my 10″; I’ve seen tinges of pink in my 15″. I also find the extra aperture great for using an O-III and pushing power on PNs.

      The mirror has delivered best views ever of planets- and really importantly, the structure moves so nicely, precisely and without backlash or vibration, that it makes high power observing a pleasure. Ive seen hints of detail within the GRS, and Io as a little ‘3d’ ball.

      NiallK, from an online thread entitled, Should I jump from 10 inches to 15 or 18?
      In my experience, the glob. clusters resolve much deeper with 10″ vs 8″. In fact, this is the main type of object where the aperture increase made a big difference. M13 and M3 became incredible with the 10″ Dob.
      Coopman(South Louisiana, USA), from an online thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

      I just bid adieu to my C8 and now have 10″ dobs as my “big” scopes. I always thought the C8 was attractive because of the easy form factor, but the extra aperture and – for me – relative ease of cooling and collimation on the dob overcame the fact that the dob is definitely bigger and a bit more of a full-contact sport to use. It does seem to me that everything on the SCT has to be much closer to spot-on to get great optical performance, and then there is the aperture difference.

      I enjoyed this thread on translating reflectors to equivalent unobstructed/refractor aperture:  https://www.cloudyni…three-7s/page-2

      Using these ideas (and setting aside impact on contrast from obstructions), it looks to me like a C8 translates to roughly 6.6″ of equivalent unobstructed aperture, while the 10″ dob is about 8.9″ – that is around 2/3 magnitudes deeper which is significant. By the same approach, a C11 comes in at around 9″ – a virtual tie with the 10″ dob. 

      WyattDavis(New Hampshire, USA), from an online thread entitled, 10″ Dob vs 8″ SCT views of a Globular Cluster?

      Sidgwick (“Observational Astronomy for Amateurs” – 1955) seems to favour that refractor over reflector notion; as does Roth ( Handbook for Planet Observers“ – 1966).

      But see this link to page 33 (2nd paragraph) of Peek’s “The Planet Jupiter” – 1958….I still remember the delight of reading that when I got my copy in 1963 – the 10” f/8 Newt followed the year after……. https://archive.org/…upiter/page/n17

      David Gray(Durham, UK), from an online thread entitled, ALPO Venus section telescope recommendation: it hurts.

      My first Dob gave me first view of so much so fast, I was totally overwhelmed. 30 years later, I still am.

      In the recent past I glimpsed a super nova in a galaxy close to Coma Bernices (I think), with my current 12 inch (SW 300P DS).

      For a £600 OTA, that is incredible.

      25585(UK), from an online thread entitled: Why we love our light buckets.

      These days it’s easily possible to have a “light bucket” with a high strehl ratio, which makes them moon/planet killers extraordinaire. Just don’t gloat about it around the high-end refractor weenies or they’ll turn purple (that’s called chromatic aberration laugh.gif).

      Nirvanix(Medicine Hat, Alberta, Canada), from an online thread entitled: Why we love our light buckets.

      I have Tak or two & some EDs. But to see further & fainter my Dobs are unbeatable. I am at my size limit physically for Dobs (wanting to stay with solid tubes), and a wee bit over spendwise for refractors. But if I had to choose just one scope to keep, it would be my 10″ F6 Dob.

      25585(UK), from an online thread entitled; Why we love our light buckets.

      These days it’s easily possible to have a “light bucket” with a high strehl ratio, which makes them moon/planet killers extraordinaire. Just don’t gloat about it around the high-end refractor weenies or they’ll turn purple (that’s called chromatic aberration laugh.gif).

      Yep. My original Light Buckets were all Coulters 13.1 then 17.5 and finally 29-inchers. They had OK mirrors for low power. I was able to get decent Deep Sky performance with the 13.1 at 115x, 17.5 at 154x and 29 at 255x (2.9mm pupil – 9x/inch); occasionally able to push them to 13x/inch. For planets, I would use off-axis stops, and got magnificent performance… actually quite astounding.

      My 36-inch New Moon with Fullum Technofusion mirror gives perfect (only atmosphere-limited) performance, full-aperture. When the thermals are behaving, I go to 438x without the resolution losing it. At that mag, it’s all about having a good scope and good atmosphere… right from the telescope on up! It’s in a dome, so I blow the heck out of the interior for a couple of hours before sunset. That makes a huge difference.

      Tom Dey (Springwater, New York, USA), from an online thread entitled; Why we love our light buckets.

      I recall with great fondness my first dob – a 2000-ish Meade Starfinder 10. Sure, the alt/az bearings were sticky as a pine tree trunk on a hot summers day, and the plastic focuser gave me fits. But those were easy to fix and with a few more minor mods, it was a beautiful scope to sail the heavens with.

      I think of dobs like sailboats – quiet, simple, peaceful and very enjoyable.

      Refractors are like small speedboats – they perform very well for their size.

      Cats are like cruise boats – they do a lot of stuff (but maybe they aren’t the best at any one of them but they’re tons of fun!).

      bbqediguana(Canada), from an online thread entitled; Why we love our light buckets.

      ***

      I researched and then observed some challenging double stars with an 8 inch reflector; have you observed any of these?

      This report is the first installment of a series of observational investigations I have made using an 8 inch f/5.9 reflecting telescope.  The goals of this project are threefold:

      1) empirically develop a predictive resolution calculator for this instrument via construction of a Treanor plot built from observations of carefully selected binaries,

      2) investigate angular separation and delta magnitude discrepancies within the WDS through observational and/or photographic examination, and

      3) provide a vetted list of double star candidates for other observers wishing to perform their own investigations.

      Methods
      All observations were conducted with an 8 inch f/5.9 Orion XT8i reflecting telescope atop an equatorial tracking platform.  Most observations were made at moderate to high power with an optical train consisting of a Paracorr Type 1 lens (setting 4), a Televue 5x Powermate, and Televue plossl eyepieces (20mm:  345x, exit pupil = 0.6 mm; 15mm:  460x, exit pupil = 0.45 mm; or 11mm:  627x, exit pupil = 0.33 mm.)  A few binaries with larger delta magnitude values were observed at lower powers (173x or 230x) by swapping out the 5x Powermate for a 2.5x Powermate.

      Double star candidates were selected by visual examination of lists generated from the WDS database using the search engine Stelle Doppie.  Generally, systems containing stars brighter than visual magnitude 10 and a separation greater than 0.56 arcsesconds were screened and sorted by constellation.  For each system the following was also conducted:  a) examination of the speckle data contained within 4th Catalog of Interferometric data; b) examination of any data provided by the Gaia satellite through the DR2 release.

      Where necessary, independent measures will be obtained using a 15 inch reflecting telescope equipped with an ASI290MM CMOS camera operating at f/13.  Data will be processed using Speckle Tool Box (STB) to generate separation and position angle data.  The bispectrum feature of STB may allow a measure of delta magnitude in some instances.

      Observations were made on nights of seeing graded as good or better (≥ 3 out of 5; Danjon scale).  Observational descriptors mostly included:  single star, elongated (or pointy), resolved (meaning two discs visible), and split (dark space seen between discs.)  Particular interest was given to objects sitting on the border of elongated and resolved—these are termed ‘limit objects’ and will be the basis for construction of the resolution calculator if the separation value is deemed accurate.

      To be considered a vetted double star candidate, Tycho satellite green channel (530 nm) magnitude data must be available (and this is what is listed.)  For each system, the separation data was scrutinized and the most accurate value was inferred by assessing the following:  last precise, orbital data (if available), speckle interferometry historical record, the author’s own measures, and/or Gaia DR2 data (if available.)  When two or more sources of separation data converged and followed the historical trend, the information was considered ‘solid’.  In many instances, the separation data was scant, inconsistent, or old; in these cases, the objects require additional measures before the observational data can be used for construction of the resolution calculator.

      Canis Major

      Hu 1240 (06200-1741) mags 8.90/9.68; pa = 239°; sep = 0.632”, 2016 (scant data)
      345x:  elongated only; below resolution limit; separation re-measure desired

      I 765 (06592-2123) mags 9.15/9.72; pa = 317°; sep = 0.586”, 1993 (data is old)
      345x:  very faint pair; pushes past elongated to resolved 20% of time with secondary seen as smaller; suspect separation is greater than 0.586”—re-measure desired

      Hu 112 (07018-1118) mags 7.03/7.70; pa = 197°; sep = 0.62”, 2014 (solid data)
      345x:  pointy in correct pa;
      460x:  snowman shape, but not resolved; just below resolution limit; will get a re-measure of separation as this is an important data point

      SEE 79 (07263-2810) mags 8.75/8.87; pa = 305°; sep = 0.721”, 2015.5 (Gaia DR2, solid data)
      552x (Pentax XO 2.5/Paracorr Type 1, setting 1):  pushes past resolved to split 50% of time, stars are two even points of light

      Bu 568 (06238-1947) mags 6.85/8.18; pa = 185°; sep = 0.849”, 2017 (solid data)
      460x:  mostly pointy, but 20% of time small secondary disc seen touching primary; just above resolution limit; surprisingly difficult—will get a re-measure of separation

      Bu 324AB (06497-2405) mags 6.56/7.93; pa = 210°; sep = 1.797”, 2015.5 (Gaia DR2, solid data)
      345x:  easily split; secondary a bit whiter and smaller than primary

      Bu 328AB (07067-1118) mags 5.70/6.91; pa = 111°; sep = 0.58”, 2003 (data is old)
      345x:  single star;
      460x:  diffraction ring brightens to show distinct secondary as resolved 20% of time;
      627x:  persistent blur in correct pa sharpens to resolved secondary 40% of time; just above resolution limit; separation re-measure desired

      Bu 753 (06287-3222) mags 7.60/5.86; pa = 43°; sep = 1.177”, 2015.5 (Gaia DR2, solid data)
      345x:  easily split, secondary is much smaller; Gaia DR2 indicates the presence of a third star:  a mag 5.9 component separated from A by ~0.52” and possessing a similar proper motion as B; WDS note:  Bu 753 is variable; will get an image to see if there are indeed three stars

      Bu 18 (06167-12) mags 7.06/8.42; pa = 286°; sep = 1.872”, 2017 (solid data)
      345x:  split without difficulty, averted vision helps visualize fainter secondary

      Canis Minor

      A 2866 (07267+0424) mags 9.34/10.04; pa = 138°; sep = 0.671”, 2015.5 (Gaia DR2, solid data)
      preliminary evidence indicates this is a limit object; unfortunately, details of observing notes are lost; will need to re-examine next season

      Lepus

      Bu 884 (05030-1226) mags 8.98/9.44; pa = 12°; sep = 0.6”, 1991 (data is old)
      345x:  at most object is pointy or elongated past being a single star; definitely below the resolution limit (too faint and too tight); re-measure of separation needed

      B 1951 (05467-2101) mags 8.54/9.48; pa = 243°; sep = 0.62”, 1991 (data is old)
      as yet unobserved; requires separation re-measure

      A 3018 (05457-1447) mags 9.43/9.39; pa = 303°; sep = 0.707”, 2017 vs 0.909”, Gaia DR2 (significant separation discrepancy)
      as yet unobserved; requires separation re-measure

      Hu 106 (06093-1141) mags 9.44/9.98; pa = 332°; sep = 0.74”, 1991 (data is old)
      345x:  viewed for a long time; was an extended rod the vast majority of the time with possible resolution to two discs <10% of the time; right at resolution limit; requires re-measure of separation

      Bu 314AB (04590-1623) mags 5.92/7.50; pa = 315°; sep = 0.73”, 4th Int. Cat. estimate
      460x:  resolved to a dot from a blur of light about 20% of time;
      627x:  similar to 460x observation but separation a bit wider when seeing allows; this object is at the limit of resolution, requires a re-measure of separation

      Bu 320AB Nihal (05282-2046) mags 2.90/7.50; pa = 8°; sep = 2.670” (2015.5, Gaia DR2, data is solid)
      230x:  very difficult because low in sky, secondary flickers into view as a tiny dot in correct pa 25% of time; at resolution limit

      Monoceros

      Bu 98 (06327-0520) mags 8.37/8.31; pa = 152°; sep = 0.58”, 2002 (data is old, scant)
      460x:  elongated only, never resolved;
      627x:  10% of time moves past elongated to show two stars of uneven magnitude just touching and (possibly resolved?); at or just below resolution limit; requires re-measure of separation

      RST 3489 (07044-1027) mags 7.40/8.45; pa = 299°; sep = 0.65”, 4th Int. Cat. estimate (scant data)
      460x:  brightening of diffraction ring in correct pa;
      627x:  persistent brightening of diffraction ring that resolves to very small secondary 20% of time; at limit of resolution; requires re-measure of separation

      STF 1157 (07546-0248) mags 7.93/7.89; pa = 173°; sep = 0.647”, 2017 (scant data)
      460x:  elongated only, never resolved;
      627x:  resolves to two discs touching about 25% of time aided by averted vision; just above resolution limit; requires re-measure to solidify separation value

      Bu 327AB (06585-0301) mags 7.80/8.15; pa = 102°; sep = 0.7”, 1997 (data is old)
      345x:  just split to two even light yellow stars; requires re-measure of separation

      A 1062 (06596-0823) mags 8.42/9.24; pa = 140°; sep = 0.68”, 4th Int. Cat. estimate (scant data)
      340x:  seen as resolved 25% of time, secondary is much smaller;
      460x:  moves past resolved to split about 40% of time; a bit above resolution limit; requires re-measure of separation

      Ho 245AB (07387-0127) mags 7.92/8.70; pa = 186°; sep = 0.668”, 2015.5 (Gaia DR2; solid data)
      345x:  brightening of diffraction ring that sharpens to very small secondary just split from primary 50% of time; significant delta magnitude discrepancy between Tycho (0.78) and Gaia (0.18); observation suggests delta mag is greater than 0.18; requires re-measure of delta mag

      A 539 (08019-0333) mags 8.80/9.54; pa = 21°; sep = 0.746”, 2015.5 (Gaia DR2, solid data)
      460x:  pointy/snowman that possibly resolves to two discs <10% of time;
      627x:  elongated only; never resolved; just below resolution limit

      AC 3 (06117-0440) mags 6.34/8.15; pa = 9°; sep = 0.64”, 4th Int. Cat. estimate (scant data)
      460x:  just pointy;
      627x:  persistently elongated but never resolved; just below resolution limit; requires re-measure of separation

      **That is it for now for this installment.  I will update this thread with additional observations and separation re-measure data as I acquire it.

      I would be interested in hearing of other’s observations of these binaries using objectives in the 5 to 10 inch range.**

      Nucleophile(Austin Texas, USA), from an online thread entitled;

      Investigations With an 8 Inch Reflector. Part I: Canis Major, Canis Minor, Lepus, and Monoceros.

      ***

      My advice is to avoid these small cats completely.  They just are not very good at anything other than being very small.  A good 80mm ED doublet would be a far better scope for planets and everything else and would not be much bigger than the VMC 95 (and I would take it over the VMC 110 too).

      Now I have not owned either of these scopes, but I have owned cats of similar aperture and they were very underwhelming to use as compared to something like a 100mm f/9 ED refractor which would do a much better job for Mars but would be far from my top choice.

      If Mars is the target of your dreams, I would try for a bigger scope like an 8″ f/6 dob. 

      The main problem with these small scopes is that by the time you get the magnification up there so that Mars will be big enough to see the Polar Caps or any surface detail as something other than being hinted at, the view will be so dim that you will probably have problems with floaters or with a grainy image.   

      An 8″ f/6 dob is a very capable planetary scope.  A far better choice for seeing Mars because these others will just show you a small, blotchy ball.

      Not that you can’t do planetary observing with a small scope. Heck, you can see Jupiter’s moons in a pair of binoculars.  The difference is that one way, you see them, and the other way, you get to observe detail on them. 

      If it must be a small Cat, shoot for a C6. If you are lucky and it has excellent optics (not something I would count on) it might do a bit better than a 100mm f/9 ED.  A C8 would be better than that, and the 8″ f/6 Newt will be better still. 

      Eddgie, from an online thread entitled; Vixen VMC-110L for Planets

       

      14.5″ F4.3 Starmaster with Zambuto mirror or 18″ F5 with Stabilite mirror. Too close to call but incredible either way. Stabilite reaches thermal equilibrium immediately so it has the best view fastest.

      scooke, from an online thread entitled; Ideal planet scope

      8″ f/6 with a Lockwood or Zambuto.

      Or my 8″ F/6. Nuff said.

      Nah, A solid tube 10″ F/8 with a Lockwood or Zambuto. That, IMO, would be the ultimate planet killer.

      That being said, my custom 8″ F/6 eats planets for breakfast.

      Hells Kitchen (Renmark, Australia) from an online thread entitled; Ideal planet scope

      stargazer193857, on 20 Dec 2018 – 8:50 PM, said:

      Discovery 8″ f7 looks like a good planetary scope. Wooden base, 1.25″ between wall and mirror. Discovery fills the gap that Orion and Zhumel left open. They charge twice as much though.

      Did someone mention a Discovery 8″ F7 scope? This is my pea shooter 8″ F7 Discovery dob which does a pretty good job with planetary views (others have told me it is an excellent planet scope after viewing through it). It also serves me well for many brighter DSO’s too. 

      I usually use either a Televue 11 plossl or Televue Nagler 13 T6 for most of my planetary viewing since I seem to live under a perpetual atmospheric jet stream. Every once and awhile, I’ll use my Nagler 9 T6 when the viewing allows it. 

      HoundDog(Louisiana, USA), from an online thread entitled; Ideal planet scope

      Slightly off topic but owning Stabilite mirrors (the original 18″F3.75 and my current 18″F5) taught me that so much bad seeing is local to the mirror. In other words thermal issues. The Stabilite mirrors showed pinpoint stars from the first moment while the 14.5″ Zambuto is thin at 1.6″ but still takes 30 minutes to an hour to show pinpoints. The star test on the 14.5 is slightly better (1/16th vs. 1/10th) but at that point it is essentially perfect either way. Thermal management is so important.

      scooke, from an online thread entitled; Ideal planet scope

      This report is the second installment of a series of observational investigations I have made using an 8 inch f/5.9 reflecting telescope. 

      Check out this link for goals and methods used in this study:

      https://www.cloudyni…-and-monoceros/

      Gemini
      STT 149 (06364+2717) mags 7.14/8.97; pa = 277°; sep = 0.733”, orbital estimate for 2019.3 (grade 2 data not a great match to historical 4th Int. Cat. data or last precise)
      627x:  at times pointy but that’s it; below resolution limit; yearly separation change is significant (components are closing); requires independent (possibly annual) measure of separation

      COU 930 (07566+1954) mags 9.10/9.29; pa = 330°; sep = 0.583”, 2008 (data is old)
      345x:  single star
      460x:  at times slightly elongated, but that’s it; below resolution limit; requires re-measure of separation

      A 2726 (06293+1233) mags 9.03/9.27; pa = 123°; sep = 0.550” (2015.5, Gaia DR2) vs 0.65”, 2015 (last precise)
      345x:  elongated rod which resolves to two discs of slightly dissimilar magnitude 25% of time; appears to be at resolution limit which supports 0.65” value for separation; 4th Int. Cat. data does not help to clarify the situation; requires re-measure of separation to solidify this value

      A 2464 (07046+1550) mags 9.13/9.78; pa = 40°; sep = 0.73”, 2016 (scant data)
      345x:  persistently notched rod
      460x:  persistent as snowman shape with slightly dissimilar magnitudes that resolves to two discs 40% of time; just above resolution limit; separation re-measure needed

      A 2868 (07292+1253) mags 8.59/8.98; pa = 22°; sep = 0.677”, 2015.5 (Gaia DR2, solid data)
      552x (Pentax 2.5XO + Paracorr Type 1, setting 1):  definitely pointy but too faint for Airy discs to be seen as distinct points of light; never resolved—just below resolution limit (will revisit next year using powermate/plossl optical train)

      Bu 1008 Propus (06149+2230) mags 3.52/6.15; pa = 252°; sep = 1.78”, 2017 (solid data)
      345x:  just split, secondary is much smaller
      460x:  easier to see as split; above resolution limit

      Leo
      STF 1423 (10192+203) mags 9.40/10.03; pa = 300°; sep = 0.600”, 2019.3 (orbital estimate; scant data)
      as yet unobserved; requires a re-measure of separation to solidify value

      STF 1555AB (11363+2747) mags 6.41/6.78; pa = 151°; sep = 0.79”, 2017 vs 0.666”, 2019.3 orbital estimate
      460x:  vacillates between snowman shape and resolved with discs of slightly dissimilar magnitude
      627x:  pushes past resolved to split 10% of time; observation supports 0.66” value for separation; 4th Int. Cat. supports a value of less than 0.79”; requires re-measure of separation to solidify value

      STF 1356 (09285+0903) mags 5.69/7.28; pa = 114°; sep = 0.878”, 2019.3 (orbital estimate; solid data)
      345x:  just split to two yellow stars of even magnitude; above resolution limit

      A 2482 (09599+1610) mags 9.26/10.07; pa = 47°; sep = 0.85”, 4th Int. Cat. estimate (data is scant, divergent)
      345x:  seen as just split 40% of time; at edge of visibility due to faintness; secondary is much smaller and barely presents as a disc; just above resolution limit; requires re-measure of separation

      Bu 105AB (09247+2611) mags 4.60/9.70; pa = 209°; sep = 1.960”, 2015.5 (Gaia DR2; solid data)
      230x:  fairly challenging; seen as split about 50% of time with secondary as very small dot quite close to the primary; above resolution limit

      Orion
      Bu 885 (05110-0146) mags 8.31/9.01; pa = 198°; sep = 0.601”, 2017 (solid data)
      345x:  extremely difficult; at most slightly elongated
      460x:  moves past elongated to a snowman shape about 20% of time
      627x:  elongated only despite best effort; this object is a bit below the resolution limit

      Bu 318 (05162-0329) mags 8.81/8.28; pa = 264°; sep = 0.643”, 2017 (solid data)
      345x:  single star
      460x:  pointy at times
      627x:  moves past elongated to resolved using averted vision 25% of time; right at resolution limit

      A 321 (05568-0304) mags 9.02/10.03; pa = 134°; sep = 0.645”, 1995 (data is old)
      345x:  pair is very faint; elongated ~entire time; resolved to two tiny dots <5% of time; at resolution limit; requires re-measure of separation

      A 2717AB (06152+0631) mags 8.07/8.98; pa = 354°; sep = 0.60”, 4th Int. Cat. estimate (data is old)
      345x:  pointy only
      460x:  moves past elongated to resolved 50% of time; requires very good seeing because components are faint; just above resolution limit—separation likely greater than 0.60”; requires re-measure of separation

      STT 517AB (05135+0158) mags 6.79/6.99; pa = 240°; sep = 0.693”, 2017 (solid data)
      394x (Pentax 3.5XW, Paracorr Type 1, setting 1):  moves past snowman shape to resolved when seeing allows; above resolution limit

      DA 4Aa,B (05354-0450) mags 4.61/7.50; pa = 203°; sep = 1.207”, 2015.9 (data is solid)
      460x:  seen steadily as just split ~entire time627x:  secondary visible 100% of time as small white dot easily split from primary; above resolution limit;
      I have observed this object (aka 42 Ori) dozens of times over the past 8 years and this was the clearest view I had ever had of the secondary—this result spurred me to change up my preferred double star eyepieces to the currently used tandem of powermate/plossl and also to initiate a detailed study of similarly challenging binaries

      Bu 190AB (05204-0802) mags 8.12/8.45; pa = 328°; sep = 0.647”, 2015.5 (Gaia DR2, solid data)
      627x:  secondary pops into view as resolved 20% of time; at resolution limit

      STT 119 (05479+0758) mags 8.08/8.93; pa = 355°; sep = 0.706”, 2015.5 (Gaia DR2, needs a confirming measure)
      460x:  mostly seen as split to two stars of uneven magnitude; above resolution limit; while the Gaia separation value ‘seems right’, this binary requires a separation re-measure due to conflicting 4th Int. Cat. data

      STF 652 (05118+0102) mags 6.26/7.44; pa= 180°; sep = 1.667”, 2015.5 (Gaia DR2, solid data)
      460x:  brightening of first diffraction ring that sharpens 50% of time to a small secondary seen as split from the primary
      627x:  more easily seen as split when seeing allows; above resolution limit; something odd here:  this object is surprisingly difficult, possibly due to the proximity of the secondary to the first diffraction ring (?); will likely re-measure separation to get more info

      DA 3 (05359-0538) mags 7.33/8.54; pa = 173°; sep = 0.860”, 2015.5 (Gaia DR2, solid data)
      345x:  snowman
      460x:  just split to two stars of uneven magnitude 30% of time
      627x:  more easily seen as split when seeing allows; above resolution limit

      STF 728 (05308+0557) mags 4.44/5.75; pa = 44°; sep = 1.281”, 2015.5 (Gaia DR2, solid data)
      345x:  just split to two white stars of uneven magnitude; above resolution limit

      HEI 670 (05500+0952) mags 5.97/8.36; pa = 264°; sep = 1.093”, 2011 (solid data)
      345x:  brightening of first diffraction ring sharpens to a small secondary seen as just split 20% of time
      460x:  more easily seen as split when seeing allows; above resolution limit
      Gaia DR2 detects a star at pa = 268° but with a separation of only 0.438”.  Observations seem to confirm separation of 1.09” vs 0.44”—could this be a triple system?  Will image to get more information

      Bu1052 (05417-0254) mags 6.68/8.22; pa = 183°; sep = 0.649”, 2019.3 orbital estimate (solid data)
      345x:  pointy (snowman) shape
      460x:  vacillates between elongated and resolved to two discs
      627x:  moves past resolved to split 10% of time; above resolution limit; surprisingly easy considering the separation and delta mag; perhaps the binary is in a ‘sweet spot’ for this telescope (?)  Should probably re-measure separation to get more info

      STF 734AB (05331-0143) mags 6.67/8.22; pa = ; sep = 1.585”, 2015.5 (Gaia DR2, solid data)
      345x:  easily split; smaller secondary is perhaps ashen in color

      Puppis
      B 1074 (07451-2855) mags 9.44/9.79; pa = 357°; sep = 0.56”, 1991 (data is old)
      as yet unobserved; will need an independent measure

      STF 1104AB (07294-1500) mags 6.39/7.60; pa = 40°; sep = 1.790”, 2019.3 (orbital estimate; solid data)
      345x: easy, wide split to two somewhat dissimilar magnitude white stars

      Bu 454AB (08159-3056) mags 6.50/8.21; pa = 359°; sep = 1.847”, 2015.5 (Gaia DR2; solid data)
      345x:  split 100% of time; considerable magnitude contrast; primary is yellow while the secondary may be light orange

      STF 1146 (07479-1212) mags 5.73/7.32; pa = 336°; sep = 1.010”, 2019.4 (orbital estimate; solid data)
      345x:  easy split; fine magnitude contrast pair with both stars appearing yellowish-white

      Have you observed any of these objects recently?  Let me know.  Or, perhaps you have a suggestion for a double I should observe—I’m all ears!

      Nucleophile(Austin, Texas, USA), from an online thread entitled; 8 Inch Reflector Investigations. Part II: Gemini, Leo, Orion, and Puppis

         

          Quid est veritas?

          Iustitia!

          My astronomical world changed forever when I first took a modern SkyWatcher 8″ f/6 Newtonian for a serious spin under a dark sky. It was far less expensive than any of the other telescopes I had personally owned, including some fine refractors and Maksutovs, and it outclassed them all on every type of celestial target. It was the sweetest of revelations!  Modest and marvellous in equal measure, Newtonians are my instruments of choice, based solely on visual performance, when I want to pursue either serious or casual observing.

          Justice, truth, fairness.

          Mr. Hardglass.

           

          Neil English is author of Chronicling the Golden Age of Astronomy

           

          Continued in Part II

           

          Book Review: “Lucky Planet” by David Waltham.

          A refreshing look at a thorny ‘scientific’ question.

          Book Title: Lucky Planet

          Author: David Waltham

          Publisher: ICON Books

          ISBN: 978-1-84831-832-8

          Year of Publication: 2014

          Price: £9.99(UK) Paperback(225 pages)

          If you are a regular reader of the popular periodicals such as Sky & Telescope, Astronomy, Astronomy Now, BBC Sky at Night Magazine, Scientific American, etc you’re sure to notice that any articles discussing life on other worlds invariably paint a picture that life is commonplace in the Universe and will be found in many different exoplanetary environments. Very rarely(if ever), will they present articles arguing the opposite; that life in general, and intelligent life in particular, will be rare or even unique to the Earth. The reasons for this bias are many and varied but some of the most important reasons include; (1) the motivations of their authors to promote their own work in astrobiology,(2) to extend methodological naturalism to the Univese as a whole and (3) to dispell the notion that we might in any way be special.

          The problem with this approach is that it is not presented in the true spirit of scientific enquiry, which seeks to find truthful answers to big questions.Thus, more often than not, the inability of these periodicals to publish scientific findings that challenge or counter their philosophic positions simply reflects the ingrained prejudice of its editorial.

          I encountered this prejudice directly in a recent exchange with the editor of Astronomy Now, a magazine that I have faithfully written for for 25 years. When I wanted to write an article discussing the idea that extraterrestrial life could be rare, citing many up-to-date scientific articles on the subject, the editor turned sour and refused to publish the work. The reason: nothing to do with science, he just didn’t like what I was reporting! A classic case of bigotry methinks. Anyway, we forgive and forget, then move on. So I decided to take my work elsewhere, no sweat. I suspect however, that my story is not unique. Many science writers before me must have experienced something similar and no doubt, it will happen to someone again in the future.

          ………………………………………………………………………………………………………………………….

          A Related Aside: Check out the hostility I received here in a recent forum discussion entitled: How many Earths in our Galaxy?  I wonder if Waltham would experience the same hostility were he to post his ideas on that forum? Diagraceful? I’d say so!

          …………………………………………………………………………………………………………………………….

           

          That’s why I was very excited about this recent book, Lucky Planet, written by one of the UK’s most respected geophysicists, David Waltham, who heads a large research team in the Department of Geosciences, Royal Holloway, University of London.

          Waltham’s thesis is this; the Earth has enjoyed more or less 4 billion year of “good weather,” and that we owe our existence to an extraordinary sequence of “lucky” happenings that have come about to make and maintain a habitable planet.  Furthermore, this unmerited fortune is very unlikely to occur on the vast majority of worlds that inhabit the observable Universe. Being used to a world teeming over with life all around us, we suffer, Waltham argues, from a severe dose of “observational bias”, which leads many to naturally conclude that life must exist everywhere. He gives some very good examples of how observational bias can lead us to wrong conclusions. For example, Waltham notes that most of the stars visible to us in the night sky are actually larger and more luminous than the vast majority of stars that really exist. But with a telescope, this bias is transformed into something much closer to the truth; that the Universe is filled with innumerable red dawrf stars much fainter and less luminous than the Sun. Indeed, as Waltham reminds us, some 95 per cent of all stars that exist are smaller than the Sun! So looks can deceive!

          The principle of mediocrity; the idea that our predicament should not be viewed as special is grounded in the Copernican principle, which Waltham discusses in chapter 2. I was especially impressed with his research on the life and works of Giordano Bruno (1548-1600), who is often cited by science popularizers as a “martyr for science,” and erroneously pedelled by science celebrities such as the late Carl Sagan, and more recently, Neil deGrasse Tyson, not to mention a great many introductory astronomy texts. Waltham convincingly argues that this is largely a scientific myth used to push a certain philosophic agenda(anti-Christian) on an unsuspecting public.

          Calling on a great deal of new scientific evidence from astronomy, planetary science and paleoclimate studies, Waltham weaves a very sophisticated scientific picture of the key events in Earth’s deep history that have contributed to maintaining a viable biosphere ever since life took a hold on the young Earth near on 4 billion years ago. Some of the facts he presents are indeed profound:

          A warming trend as small as 1 degree C every 100 million years would have been enough to make our world uninhabitable by now, and it would not have been surprising had such a trend occurred.

          pp 47

          Much of the science in the book derives from Waltham’s own work in theoretical modelling of paleoclimates, as well as geology field work, with many amusing anecdotes along the way. When he was a boy, for example, he lived for a time on the west coast of Scotland, where his love of fossils and geology was nurtured. As a teenager, he became a keen amateur astronomer, with a particular love for the Moon, and even built a few reflecting telescopes, but like myself, drifted away from astronomy for a period to pursue his education in physics, only to return to important astronomical topics later in his career. And though he does not acknowledge the work of a Creator as the explanation for this extraordinary serendipity, he remains respectful of those who do hold religious beliefs.

          The book continues with excellent, well-informed chapters on Big Bang cosmology, a spectacularly successful scientific model for the origin and evolution of the Universe, the stabilising effects of the Earth’s Moon, the role of James Lovelock’s Gaia theory in attempting to explain the many inter-related factors that maintain a complex biosphere, and how it fares in comparison to his own ‘Goldilocks’ view of Earth, where luck was the pre-eminent factor in our planet’s success. He appeals to the anthropic principle quite a bit in the book and its usefulness in explaining why the Universe as a whole appears fine-tuned for life.

          That said, the book does display a few significant shortcomings. In a biological context, he uses the word “evolution” more like a magic wand than a proper scientific tool. Stars, planets and galaxies evolve because we can model their evolution with a fair degree of precision. But the same has not been demonstrated for the most complex things we know about; living systems. All we hear is ‘this evolved into that,’ with no explanation as to how it happened. And details are very important when trying to convey scientific truths. He rates Charles Darwin as a significant scientific figure, whereas I do not. There is little discussion on the details of how life arose except the usual handwaving about some mysterious ocean floor vent,  and a ‘just so’ story of how replicating RNA models were miraculously encapsulated into a fully viable lipid membrane and the like. I got the distinct impression that Waltham did so in a rather tongue in cheek manner, as if he were toying with his readers. Later in the book he alludes to this shortcoming in the context of computer modelling:

          It may seem surprising that the Moon could provide the best evidence of the Earth’s life-friendliness when other factors, such as biological evolution, have had a much more direct and significant impact on our planet’s developing environment. There are several reasons why the Moon tells a more convincing story of our good fortune than many other, apparently more promising, facets of our world. For a start, the behaviour of the Earth-Moon system is reasonably well understood one, controlled by the relatively simple equations of celestial mechanics. I say ‘relatively simple,’ because the details are still a bit of a nightmare. Isaac Newton himself complained that thinking about the motions of the Moon made his head ache! Nevertheless, unlike climate evolution or the evolution of animals and plants, the changing behaviour of our satellite through time can be mathematically modelled with reasonable precision.

          pp 184

          I applaud the intellectual honesty of Waltham in an age where many inflated scientific egos assert that we have nearly everything figured out. Science itself is evolving; it never ceases so long as inquisitive minds keep seeking answers. What may be true today may not be true tomorrow. He writes;

          I should in all honesty admit that experts would argue over almost every one of the details in the story I have just given…..

          pp 61

          I was also surprised by his avoidance of providing an in-depth discussion on the Cambrian Explosion, which occurred about 541 million years ago and which led to 80 per cent of extant animal body plans suddenly appearing within a short span of 10 million years, and with no credible evolutionary antecedents. Indeed, we now know the fossil record as a whole does not support an evolutionary narrative, with vast periods of stasis interspersed with mass extinctions followed by equally rapid appearances of new species and ecosystems. Waltham would have also benefitted from the work of the world-renowned synthetic organic chemist, Professor James Tour, who has recently weighed in to expose the shocking degree to which human intervention is needed to reproduce even the very first steps toward the simplest of lifeforms. Suddenly, Waltham would have to thank his lucky stars many times over again for all the other convenient happenings in Earth history!

          How I wish Waltham were as enthusiastic about the details of living systems as he clearly is about rocks!

          Having said all that, Waltham does concede that the origin of life will be a very unlikely event anywhere;

          I believe that the origin of life, like all the major steps leading to the emergence of intelligence, is a rare occurrence.

          pp 208

          I think that’s quite an understatement!

          In addition, Waltham hopes that future robotic or human explorers will one day uncover evidence that Mars has (or had) microbial life but offers this very sensible qualification:

          My hope is that we will soon find microscopic life living beneath the surface of Mars and my expectation is that its biochemistry will show it to be similar to Earth life. This will generate some interesting discussions as we debate whether the evidence that there is only one way to make life or evidence for cross-contamination between the worlds. I expect a consensus to eventually emerge that the similarities are too great to be explained by a separate origin…

          pp 208

          As you can see from the internet thread I linked to above, I got lampooned for asserting that the question of whether life is commonplace in the Universe is not really scientific in the sense that we should not expect it to be commonplace in the Cosmos. In other words, it is scientifically naive to assume so. Professor Waltham affirms the same general conclusion in stating that the scientific consensus will very likely fall on the side of extreme rarity rather than ubiquity. He writes;

          The scientifically conservative position should be that life is rare and intelligence even more so.

          pp 186.

          He even advises that others should have a similar frame of mind about the Earth:

          I certainly believe that the possibility that the Earth is special should be taken seriously by everyone and for all sorts of reasons, but in conclusion, I’d like to finish with the most important justification of all for considering this idea. It’s probably true.

          pp 212

          Waltham is a very engaging and likeable intellect; a deep thinker, who kicks back hard against the goads.

          Clearly, our Dave put lot of thought into this book. But I sense he is searching for something. He is deeply intrigued by the perfect solar eclipses we experience, whether it is merely a highly unlikely coincidence or whether it points to something far greater, and even describes his trip along with a few chums, to Germany to get a good view of the August 1999 apparition. He often gives thanks to the powers that be (let’s call it the goddess Fortuna) for how lucky he feels to have existed at all! He even ends with a surprising comment; and this from a man who cannot, by his own admission, believe in miracles:

          I will not finish on a negative note. Earth and countless other inhabited worlds scattered thinly throughout an unimaginably immense multiverse has given rise to a fragile wonder of life. On Earth we have laughed, loved and wondered at the beauty of the world and the Universe around us. We are part of an extraordinary miracle and I, for one, feel very lucky.

          pp 214.

          So although Waltham’s goddess – Fortuna – allows for life bearing planets but only so rarely that one or two might exist in each galaxy at the most, or galaxy cluster, he also plays mind games with himself. I was particularly intrigued by these comments:

          Acceptance that the Earth is a very odd planet, and that this was necessary for the emergence of humans, also has a very obvious impact on the search for extraterrestrial intelligence. Quite bluntly, if there is significant anthropic selection for Earth properties, then we are effectively alone in the Universe. As I discussed earlier, the nearest extraterrestrial civilization could easily lie beyond the edge of the visible Universe and so be uncontactable. This is quite a disappointing conclusion for many. Indeed, one prominent, well-informed critic of the anthropic ideas has admitted that his views may be coloured by having grown up watching the original ‘Star Trek’ series. Maybe my own views have been coloured by slightly more recent films. I’ve thought for a long time that ‘Alien’ was more plausible than ‘Mr. Spock’, so it’s quite possible that my subconscious doesn’t want aliens to exist.

          pp 211

          I can empathise with the author here, as my own position is that we are alone.

          And there’s a good reason for that!

          On my sojourn through this extraordinary labrynth we call life, I have lost my faith in Fortuna; for she acts blindly, with no foresight and cannot create; always fumbling in the dark.

          Neither does she care.

          But, 20 centuries ago, an extraordinary human being walked the dirt roads of the Galilee, bringing Light to the world, a manchild born in a manger, who grew in wisdom and stature, healed the sick and the infirmed, fed the masses with little more than a morsel of food and even commanded the winds to die down. By turning water into choice wine at a wedding, He gladdened the human heart. He raised the dead, walked on water, and after suffering a horrific execution on a Roman cross; rose triumphantly from the dead and appeared to more than 500 believers before ascending on the clouds to Heaven. In the Holy books written concerning Him we read:

          He is the image of the invisible God, the firstborn over all creation.  For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him. And He is before all things, and in Him all things consist.

          Colossians 1:16-17

          This Person chose to enter His own creation and cared Himself to death.

          His name is Yeshua of Nazareth, and He promised to return to this Earth, which He created, to bring an end to all evil, suffering and death. The same holy books say that every knee shall bow and every tongue confess that He is Lord.

          I joyfully await His return, and would encourage Dr. Waltham to research His truth claims. He brings joy and meaning to my life; Yeshua; the eternally Living God, who will not share His glory with another.

          So, to end this review, and despite the few reservations I have with it, I would heartily recommend this book to anyone wishing to get an up-to-date and scientifically accurate picture of how we got here. It is a very well written work, full of joy, wonder, humour and optimism; a book that will help you appreciate just how wonderful every human life is!

          Errata:

          pp 49 the author says the Orion Nebula is a few hundred light years away. It’s actually about 1,350 light years distant.

          pp 54 The author says that Banded Iron Formations(BIFs) cannot form in the presence of oxygen.

          BIFs are formed when aqueous iron ions combine with oxygen forming insoluble oxides which form precipitates known as BIFs.

           

           

          Neil English regularly kicks against the goads, and is author of a new historical work; Chronicling the Golden Age of Astronomy, published by Springer-Nature.

           

          De Fideli.

          Beginner Telescopes

           

          The ShortTube 80: ready to go to work.

          In this age we live in, choosing a good beginner telescope can be a daunting task, what with all the models that are flooding the market. In this article, I  would like to discuss the potential of several telescopes that offer good value for money and will allow their owners to grow in the hobby.

           

          Tune in soon for details…………………..

           

          De Fideli.

          A Brief Commentary on the Holy Scriptures; Tree of Life Version(TLV).

          Seeing Scripture through Jewish eyes.

          A song: a psalm of Asaph.
          God, do not keep silent.
          Do not hold Your peace, O God.
          Do not be still.
          For look, Your enemies make an uproar.
          Those who hate You lift up their head.
          They make a shrewd plot against Your people,
          conspiring against Your treasured ones.
          “Come,” they say, “let’s wipe them out as a nation!
          Let Israel’s name be remembered no more!”
          For with one mind they plot together.
          Against You do they make a covenant.

                                                                                                                                  Psalm 83: 1-5

           

          Are you looking for a brand-new Bible experience? Are you searching for a translation of the Bible that restores some of the Hebrew names and terminology found in the original manuscripts? Perhaps you are looking for a Bible that will help you rekindle an interest in the sacred words of Scripture seen from a Messianic Jewish perspective? If so, I have just the recommendation for you; enter the Tree of Life Vesion(TLV).

          The brain child of this ambitious project was Daniah Greenberg and her Rabbi husband, Mark Greenberg, who assembled a cadre of Messianic Jewish Bible scholars to create an all-new translation of the Holy Scriptures that gives the reader a solid flavour of the original Hebraic overtones of the Bible, with a decidely Jewish accent. But it was no small feat, given the proliferation of English Bible versions flooding the global market. Daniah had the courage and conviction to raise the funds to pay for soild scholarship within the Jewish cultural tradition, which culminated with the first edition of the TLV Bible in 2011. Daniah Greenberg now serves as President of the Messianic Jewish Family Bible Society. Greenberg is also CEO of the newly established TLV Bible Society.

          It pays to remember that all the Biblical writers, with the possible exception of the author of the Book of Job, were Jews. Jesus Christ was Jewish. The earliest Christian meetings took place in synagogues and despite the attendant evils of anti-semitism throughout history, and its giving rise to unbiblical ideas such as replacement theology,  it is undoubtedly the case that unique insights into much of the Biblical narrative has come from the Jewish mindset. Seen in this light, it is not at all surprising that a new Bible translation made by the original people to which the Lord of all Creation first appeared should find a place on the bookshelves of many Christians in the 21st century.

          The first thing you will notice about the TLV is the unfamiliar ordering of the books of the Bible, which have been re-presented in the order rendered in the Jewish tradition, which Christians refer to as the Old Testament. In Jewish parlance, these are the books of the Tanakh.

          As you can see from the table of contents below, the Tanakh is further divided into three sections; the Torah (Law of Moses or Pentateuch), the Neviim (The Prophets) and the Ketuvim (The Writings).

           

          The unique ordering of the books of the Old Testament(Tanakh), as experienced by Orthodox Jews.

          The books of the New Testament(Good News) are presented in their traditional order. The reader will note that the Book of James is titled ‘Jacob,’ and Jude is titled ‘Judah, which  represent their transliterated Jewish names.

          The New testament books are presented in their traditional order, with two transliterated names, Jacob(James) and Judah(Jude).

          A sizeable number of words are presented in the original Hebrew. For example, YHWH God’s covenant name, is often referred to as Adonai,  but also as Elohim (Creator). Jesus is denoted as Yeshua, Mary(the mother of Jesus) is given her original name, Miriam; Spirit is presented as Ruach, the Levitical priests, Kohanim, the children of Israel, B’nei-Israel and Sabbath is translated as Shabbat. All Hebrew terminology can be referenced at the back of the Bible in the form of a tidy glossary. There is even a section which helps the reader pronounce these Hebrew words correctly. That said, once you get into the TLV, most of the terms sink in very easily and naturally and so provide the reader with an education in basic Hebrew religious terminology. The addition of original Hebrew words also adds to the poetic beauty of the language of the Scriptures, which are readily appreciated while reading through.

          Each book of the Holy Scriptures is accompanied by a short introduction written by Messianic Jewish scholars, which provides a concise overview of the most important ideas developed in the texts. The translators intentionally chose to produce a translation that is at once respectful to more traditional translations of the Bible such as the Authorized King James Version (KJV), and more modern translations such as the English Standard Version (ESV) and New American Standard Bible (NASB), retaining some classic Biblical terminology such as “Behold“, “lovingkindness” and “Chaldeans.” For example, in the opening verses of the Book of Esther, the TLV refers to the Babylonian King as Ahasuerus and not Xerxes ,as you will find in looser translations such as the NIV and NLT.

          This is what happened in the days of Ahasuerus, the Ahasuerus who reigned over 127 provinces from India to Ethiopia.

          Esther 1:1

          In keeping with the original customs of the first Christians, the word ‘baptism‘ does not appear in the TLV, being replaced by the more appropriate term, ‘immersion.’ This is entirely justified as infant baptism was not practiced by the earliest followers of Yeshua. Consider this passage from Acts 2;

          Peter said to them, “Repent, and let each of you be immersed in the name of Messiah Yeshua for the removal of your sins, and you will receive the gift of the Ruach ha-Kodesh.

          Acts 2:38

          John the Baptist is likewise referred to as “John the Immerser”

          Unlike virtually all other Bibles in the English language, the Adversary’s name is presented in lower case, ‘the satan‘; a most appropriate demotion to honour the ‘father of lies.’ Consider, for example, the opening passages of the Book of Job:

          One day the sons of God came to present themselves before Adonai, and the satan also came with them.  Adonai said to the satan, “Where have you come from?”

          The satan responded to Adonai and said, “From roaming the earth and from walking on it.

          Adonai said to the satan, “Did you notice my servant Job? There is no one like him on the earth—a blameless and upright man, who fears God and spurns evil.”

          Job: 1:6-8

          Another interesting aspect of the TLV is that it quite often departs from the usual preterite, or imperfect tense one normally experiences in traditional translations. Consider this passage from the Gospel of Matthew Chapter 4 in the NASB:

          Again, the devil took Him to a very high mountain and *showed Him all the kingdoms of the world and their glory;

          Matthew 4:8

          Now consider the same passage in the TLV:

          Again, the devil takes Him to a very high mountain and shows Him all the kingdoms of the world and their glory.

          Matthew 4:8

          These occasional departures add to the immediacy of the situation as if it were happening right now! This is a powerful linguistic tool that the TLV scholars used to evince the poignancy of certain passages of Holy Scripture.

          The poetic books of the Holy Scriptures, such as the Psalms, are most beautifully rendered and retain traditional  terms like Selah (an uncertain word thought to refer to an interlude in a musical performance). Consider, for example, Psalm 24 in the TLV:

          A psalm of David.
          The earth is Adonai’s and all that fills it—
          the world, and those dwelling on it.
          For He founded it upon the seas,
          and established it upon the rivers.
          Who may go up on the mountain of Adonai?
          Who may stand in His holy place?
          One with clean hands and a pure heart,
          who has not lifted his soul in vain,
          nor sworn deceitfully.
          He will receive a blessing from Adonai,
          righteousness from God his salvation.
          Such is the generation seeking Him,
          seeking Your face, even Jacob! Selah
          Lift up your heads, O gates,
          and be lifted up, you everlasting doors:
          that the King of glory may come in.
          “Who is this King of glory?”
          Adonai strong and mighty,
          Adonai mighty in battle!
          Lift up your heads, O gates,
          and lift them up, you everlasting doors:
          that the King of glory may come in.
          “Who is this King of glory?”
          Adonai-Tzva’ot—He is the King of glory! Selah

          Psalm 24

           

          The reader of the TLV Holy Scriptures will note that the word “church” does not appear in this translation. Instead, the scholars chose to use the words “Messiah’s community.” This is an acceptable change, as the word they were probably translating was the Greek term ecclesia, which appears in the New Testament 115 times and was often associated with a civil body or council summoned for a particular purpose. The nearest the Greek language gets to “church” is kuriakos, which is best understood as “pertaining to the Lord,” which probably morphed into the Germanic “Kirche” or “Kirk,” which is still used in northern England and Scotland to this day.

          An amusing aside: Has anyone ever referred to Kirk Douglas as ‘Church Douglas’, who just happens to be an orthodox Jew?

          These translative nuances matter little in the scheme of things however. Acts 11 provides a good illustration of these translation choices:

          Then Barnabas left for Tarsus to look for Saul, and when he had found him, he brought him to Antioch. For a whole year they met together with Messiah’s community and taught a large number. Now it was in Antioch that the disciples were first called “Christianoi.”

          Acts 11:25-26

          Note also that the TLV translation team used the Greek term for Christians, ‘Christianoi‘. This is also perfectly acceptable, as there was no Hebrew word for ‘Christian’ in those early days.

          The scholars who created the TLV chose to use the latest manuscript evidence, which included much older texts found in the modern era compared with the King James or New King James, for example(which are based on the Textus Receptus). It thus follows a similar translation ethos to other popular Bibles in the English language such as the NIV and ESV.  On the spectrum of modern English Bible translations, which vary from the highly literal, so-called ‘word for word’ renderings, through the less literal ‘thought to thought’ translations, I would categorise the TLV as adopting a ‘middle of the road’ approach. Perhaps the best way to illustrate this is to look at the same passage of Scripture in a few translations. Consider, for example, the highly literal NASB rendition of Matthew 9, verses 1 through 8:

          Getting into a boat, Jesus crossed over the sea and came to His own city. And they brought to Him a paralytic lying on a bed. Seeing their faith, Jesus said to the paralytic, “Take courage, son; your sins are forgiven.” And some of the scribes said to themselves, “This fellow blasphemes.” And Jesus knowing their thoughts said, “Why are you thinking evil in your hearts? Which is easier, to say, ‘Your sins are forgiven,’ or to say, ‘Get up, and walk’? But so that you may know that the Son of Man has authority on earth to forgive sins”—then He said to the paralytic, “Get up, pick up your bed and go home.” And he got up and went home. But when the crowds saw this, they were awestruck, and glorified God, who had given such authority to men.

          Matthew 9:1-8(NASB)

           

          Next consider the TLV equivalent:

          After getting into a boat, Yeshua crossed over and came to His own town. Just then, some people brought to Him a paralyzed man lying on a cot. And seeing their faith, Yeshua said to the paralyzed man, “Take courage, son! Your sins are forgiven.” Then some of the Torah scholars said among themselves, “This fellow blasphemes!” And knowing their thoughts, Yeshua said, “Why are you entertaining evil in your hearts? For which is easier, to say, ‘Your sins are forgiven,’ or to say, ‘Get up and walk’? But so you may know that the Son of Man has authority on earth to pardon sins…” Then He tells the paralyzed man, “Get up, take your cot and go home.” And he got up and went home. When the crowd saw it, they were afraid and glorified God, who had given such authority to men.

          Matthew 9:1-8(TLV)

           

          Finally, consider the same passage from a thought for thought translation like the NIV:

          Jesus stepped into a boat, crossed over and came to his own town. Some men brought to him a paralyzed man, lying on a mat. When Jesus saw their faith, he said to the man, “Take heart, son; your sins are forgiven.” At this, some of the teachers of the law said to themselves, “This fellow is blaspheming!” Knowing their thoughts, Jesus said, “Why do you entertain evil thoughts in your hearts? Which is easier: to say, ‘Your sins are forgiven,’ or to say, ‘Get up and walk’?  But I want you to know that the Son of Man has authority on earth to forgive sins.” So he said to the paralyzed man, “Get up, take your mat and go home.” Then the man got up and went home.  When the crowd saw this, they were filled with awe; and they praised God, who had given such authority to man.

          Matthew 9:1-8(NIV)

          I think it is reasonable to conclude that the TLV is a good compromise between both translation philosophies, distinguishing itself by means of introducing some Hebrew words and names but also in the way that the translators have chosen to alter the tense of some passages, as discussed previosuly.

          The TLV  also follows many of the newer Bible versions in adopting a more gender neutral approach to terms such as ‘Brethern’ or ‘Brothers’. For example, the TLV renders Galatians 1:11 thus:

          Now I want you to know, brothers and sisters, that the Good News proclaimed by me is not man-made.

          Galatians 1:11 (TLV)

          Compare this to the more conservative ESV:

          For I would have you know, brothers, that the gospel that was preached by me is not man’s gospel.

          Galatians 1:11 (ESV)

          And the NIV:

          I want you to know, brothers and sisters, that the gospel I preached is not of human origin.

          Galatians 1:11(NIV)

          Some commentators have expressed concern that the Bible should never be altered so as to express political correctness, as in this case, where ‘brothers’ is altered for the sake of inclusiveness to read, ‘brothers and sisters.’ I understand their concerns but I have no strong opinion either way on this issue, so long as the context of the particular verse is not altered.

          The TLV does have a couple of errors which I picked up while reading through the translation. The first appears in Jeremiah 34:14

          At the end of seven years you are to set free every man his brother that is a Hebrew who has been sold to you and has served you six years; you are [to] let him go free from you.’ But your fathers did not obey Me, nor inclined their ear.

          I have inserted the missing word in bold brackets that makes the sentence comprehensible.

          In addition there is a printing error in my Large Print Personal Size TLV on page 902 and 903, the heading of which reads “Obadiah 9” and “Obadiah 1,” respectively. Since these headings are meant to illustrate the chapter numbers, they are clearly unecessary as the Book of Obadiah only has a single chapter.

          The typographical error niggled me at first (as an avid reader, I’m very tolerant of typos in general but view Holy Scripture in a more exalted light), but I understand that these things happen. I have written to the TLV Bible Society informing them of these issues which I hope they will be able to resolve in due course.

          Some comments on the physical presentation of the TLV Holy Scriptures

          The author’s TLV large print copy of the Holy Scriptures.

          I was very impressed with the quality of the giant print personal size TLV that I acquired back in January 2018. It has a beautiful leathertex cover, which is soft and durable. Indeed, the current selection of faux leather Bibles(in many translations)are amazing value for money, and are superior to the cheap, bonded leather found on premium Bibles just a decade ago. The TLV also has a smyth-sewn binding for greater durability even with prolonged use.

          The Personal Size Giant Print TLV is about 9 inches long and 2 inches thick.

          It has a paste-down liner, a highly readable 12.5 font size, beautiful gold gilded pages and comes with a single ribbon marker. I especially like the paper used by Baker Books(the publisher of the TLV), which is a more creamy white than the usual white pages seen n many other of my Bibles.As seen below, the text is presented in a double column format and has a generous number of cross-references. The text is line matched and shows minimal ghosting, which annoys some people more than others.

          The paper in the TLV is an off white(creamy), the text is double columned, shows little bleed-through, with clear 12.5 sized font.

          The back of the TLV has an extensive concordance, a short glossary explaining the Hebrew terms used in the translation, as well as a short section of prayers (including the Aaronic benediction and the Lord’s Prayer) and other  blessings for those who wish to learn a little more Hebrew. A couple of maps show Yeshua’s travels in the 1st century AD as well as a modern map of Israel. Best of all, you can acquire all of this for a very modest price: I paid about £25 for my copy but you can also get it at discounted prices from smaller retailers. See here for just one example.

          I would highly recommend the TLV to avid readers of the Bible. It will come in especially handy when witnessing to Jews but can be enjoyed by anyone who appreciates the deep Hebrew roots of the Christian faith.

           

          Dr Neil English shows how the Christain faith has inspired visual astronomers over the centuries in his new historical work; Chronicling the Golden Age of Astronomy.

           

          Post Scriptum: You can also read the TLV(or indeed any other Bible translation) online by visiting BibleGateway.com

           

          De Fideli.

          In Praise of Barlow Lenses.

          Three fine, low-cost shorty Barlows, ideal for use with my Newtonian reflectors. From left to right: the Meade 3x, the Orion shorty Barlow 2x and the Astroengineering 1.6x Barlow.

          In this day and age, where almost every item of equipment we use under the stars is taken for granted, it pays to remember that we have a lot to thank our astronomical forebears for. A case in point is the humble Barlow lens, which has enjoyed a very long and illustrious history with visual observers, where today it remains an indispensable tool as well as a cost-saving device for the amateur astronomer.

          Contrary to popular belief, the concept of the Barlow lens does not reside entirely with the musings of the English mathematician Peter Barlow (1776-1862), but actually had its origination in the fecund mind of the 18th century German philosopher and mathematician, Christian Wolff (1679-1724), who first conceived of the idea of adding a concave lens ahead of the eyepiece but behind the objective of a telescope  in order to provide greater magnification and with a slight increase in focal length. The result had mixed fortunes however, in that the resulting images in an achromatic telescope, while certainly enlarging the image, also deteriorated the achromatism achieved by the combination of the crown & flint object glass.

          Charistian Wolff(1679-1724) : the originator of the Barlow lens concept in the 18th century. Image credit; Wiki Commons.

          The problem was once again studied with renewed vigour in the first half of the 19th century, when Peter Barlow, then a Professor of mathematics at the Royal Military Academy, Woolwich, England, computed the design of an achromatic concave lens which was made by the optician, George Dollond, and mounted in a telescope where it showed very promising results. Some of the earliest ‘guinea pigs’ to experiment on the new device included the Reverend William Rutter Dawes and the Admiral William H. Smyth, who both commented favourably on the new contraption as early as the late 1830s and early 1840s, reporting that the image was left just as colour free as when the telescope was used without the contrivance, even allowing them to vary the magnification at will by moving the doublet lens either towards or away from the ocular lens.

          The device, now commonly known as the Barlow lens, enjoyed rapid success. This author is reminded of the work of the astronomers serving in the employ of the Victorian tycoon, George Bishop, who had set up a lavishly-equipped private observatory in 1836 at South Villa, Inner Circle, Regent’s Park, London, where the Barlow lens is vividly described:

          An achromatic lens( the macro-micro lens), which slides into the tube of the micrometer, was frequently used by Mr. Dawes in his observations of double stars. The effect of the interposition of this lens is to increase the magnifying power nearly in the ratio of two to one, without any very serious diminution of light. It is, therefore, of great service in the measurement of difficult objects which require increase in power with considerable light.

          xii-xiii Bishop, G., Astronomical Observations Taken at the Observatory , South Villa, Inner Circle, Regent’s Park, London, During the Years 1839-1851

          How does a Barlow work? Because it is a negative(diverging) lens consisting in its most basic form as either an air-spaced or cemented crown-flint doublet, it changes the angle of convergence, making it longer, as though the beam were coming from an objective lens or primary mirror with a longer focal length. What this means in effect is that a 2x Barlow will double the effective f ratio of your telescope, turning an f/5 system into an f/10. And though the Barlow lens can introduce some additional errors into the optical train, if well made, it will almost certainly remove more aberrations than it generates. This is easy to see when using an ordinary eyepiece, such as a 20mm Plossl or some such, in a fast optical system like my two Newtonian reflectors. Used without a Barlow lens, the 20mm Plossl will give very good on-axis performance but less so off-axis. Now insert a 2x Barlow lens ahead of the eyepiece and the off-axis performance is considerably improved! That’s because the cone the eyepiece ‘sees’ looks like an f/10 optical system and not an f/5 system.

          In the days before anti-reflection coatings, Barlow lenses caused a small but noticeable reduction in image brightness, as well as the odd ghost image due to internal reflections, especially on bright objects, but with modern multi-coatings appplied to all air-to-glass surfaces, this light loss is reduced to negligible levels(~3 per cent).

          Barlows come in all shapes and sizes, offering magnification boosts in the range of 1.6x right up to 5x. That said, by far the most commonly used Barlow lenses offer powers of either 2x or 3x. In general, longer Barlow lenses tend to give greater magnification boosts than shorter ones, but there are always exceptions.What is more, the power printed on the barrel may not be the power you get in field use, but it’s normally quite close. In addition, with refractors that employ 90-degree star diagonals, a 2x Barlow used in normal mode can also give a 3x boost if screwed into the front of the same diagonal. Bear in mind though that most modern Barlow lenses are intended for use at the power they show on the barrel and may not perform quite so well when moved to provide a different magnification. One should always avoid models offering a range of magnifications by moving the optics in a sliding tube, for example.

          The Barlow lens has the inherent property of increasing the eye relief of any eyepiece used in combination with it. This is of considerable advantage to those who enjoy very short focal length Plossl and orthoscopics, for example, which by nature offer amounts of eye relief broadly similar to the focal length of the ocular used and thereby improving the degree of viewing comfort experienced by the observer.

          With my fast (f/5) Newtonian telescopes, I have found through experience that shorty Barlows are better than their longer counterparts, because they always reach focus with them.That said, shorty Barlows also increase eyerelief more than longer Barlows. I have used this to great effect in my study of double stars with a 130mm f/5 and a much larger 305mm f/5 Newtonian. For example, when combined with one of my favourite eyepieces used to resolve close binary systems; a Parks Gold 7.5mm ocular, a 3x Meade shorty Barlow provides a supremely comfortable field of view at 260x in the 130mm telescope with wonderful, edge-to edge-sharpness.

          Another favourite with a Barlow lens is my old 4.8mm T1 Nagler. This high power eyepiece delivers a magnification of 135x in the 130mm f/5 by itself but the eye relief is quite tight. All that changes though when I use it in conjunction with my 2x or 3x Barlow lenses (yielding powers of 270x and 405x, respectively). Eye relief is much improved and the views that little bit more enjoyable!

          When Barlowing longer focal length eyepieces, care must be taken to ensure it does not strongly vignette the outer part of the eyepiece field. If the field stop of the eyepiece is greater than the clear aperture of the Barlow, then it will cut off some of the light coming from the outer sections of the eyepiece, resulting in significant light loss and a reduction in the true field presented. Look at the two Barlows shown in the image below, for example. The Barlow shown on the left is the Orion 2x shorty Barlow and the one on the right is the 3x Meade Barlow. Note the larger clear aperture of the former, which makes it better suited for magnifying low-power, long focal length oculars.

          The 2x Orion Shorty Barlow(left) is better suited to boosting the power in long focal length eyepieces.

          In recent years, a number of firms have brought to market so-called “apochromatic” Barlow lenses with some kind of low dispersion glass included in the prescription. These can often be sold at higher prices than regular, “achromatic” Barlow lenses with the implication that they will perform better. This is nonsense however, as a good achromatic doublet with properly applied anti-reflection coatings will give essentially the same performance. Indeed, one of the first ‘apo’ Barlows this author has experienced; the Meade # 140; performed significantly worse in field tests than a standard achromatic system costing half as much! The truth of course, is that the introduction of apochromatic Barlows is yet another clever marketing gimmick that has caught more than a few tyros off guard. As proof of concept, consider the excellent Barlow lenses long offered by well established firms such as TeleVue, who make some of the best long Barlows money can buy. You won’t have to look long to see that all of the Barlows Albert Nagler has brought to market are well-made achromatic doublets. If there were an advantage of including low dispersion glass in their prescription, don’t you think Uncle Al would have done it long ago?

          Nor will a Barlow lens improve the colour correction of an achromatic refractor, as some amateurs have claimed on the vulgar forums. The dispersion caused by the achromatic doublet is completely unchanged when using a Barlow lens. Neither will it increase the depth of focus of the telescope when used normally. That said, Barlows can certainly help achieve larger fields that are corrected for the Seidel aberrations such as coma, for example, which can be mildly annoying to those who use fast f/4 and f/5 relative apertures.

          Consider a case in point: the coma free field of a Newtonian system in millimetres, scales directly as the cube of focal ratio. Specifically;

          The coma free field = 0.022 x f^3.

          So, for my f/5 Newtonian we obtain a coma free field = 0.022 x 5^3 = 2.75mm.

          Next, consider how this translates into true field.

          True field in radians is given by; coma free field/ focal length.

          Thus, the true coma free field in the 650mm Newtonian will be:

          (2.75/650) = 0.0042 radians, and then converting to angular degrees gives 0.0042 x 360/2pi = 0.24 degrees.

          Consider next a typical high−power eyepiece used in double star divination. As mentioned above, one of my favourite combinations for close double star work is a 7.5mm Parks Gold coupled to a 3x Barlow lens, with an apparent filed of view of about 50 degrees. This yields a power of 260 diameters in the 130mm f/5, so the coma free field at this enlargement is: 260 x 0.24 = 62.6 degrees!

          This means that there is no coma to worry about across the entire field of view using this particular configuration. Barlows will similarly reduce the effects of other Seidel aberrations in similar fashion(though to a varying degree corresponding with how those said aberrations fall off with focal ratio). This helps keep the images of the stellar disks nice and crisp as they move from one side of the telescopic field to the other.

          Barlow lenses are cost-saving devices too. Indeed, a savvy telescopist can dispense with acquiring  a complete set of half a dozen eyepieces say, and instead choose just two or three oculars and a Barlow lens(or two) to achieve the range of magnifications one desires from the telescope. For example, if you have a 25mm and 8mm Plossl, as well as a 2x Barlow used with a telescope with a focal length of 800mm, you can get a nice range of powers;  32x, 64x, 100x and 200x.This is especially true since good Barlow lenses can be had for considerably less money than a fixed focal length eyepiece. My own Barlow lenses cost between £20 and £30 and perform handsomely with virtually all eyepieces I couple them to.

          For those folk who dislike the change in eye relief caused by a Barlow lens they should consider telecentric devices like those marketed by TeleVue( the Powermate) and Meade. These will not increase the eye relief you get with a given ocular and also maintain the same focus position one enjoys when the eyepiece is used alone. They are however, considerably more expensive than regular Barlows.

          Barlows also have a very important role to play in astro-imaging, particualrly high-resolution lunar and planetary photography, where they provide very effective focal length boosts and thus an appropriate image scale. They are also supremely useful in binoviewing, by decreasing the amount of in-focus travel necessary to achieve focus with many of these devices.

          So, in summary, Barlow lenses serve as very important tools for the modern visual observer and imager alike, and are thus very unlikely to go out of fashion any time soon. Good ones can be had fairly inexpensively and will provide the user with a lifetime of applications.

           

          Neil English is author of Choosing and Using a Dobsonian Telescope.

           

           

           

          De Fideli.

          For the Record: My Telescope & Binocular Collection.

          Duodecim:

          Duodecim: 12″ f/5 Newtonian.

          12″ f/5 Revelation Dobsonian with ultra-high reflectivity coatings on original mirrors, 23 per cent central obstruction. Used regularly.

           

          Octavius:

          Octavius; optimus.

          8″ f/6 Skywtacher Dobsonian wth ultra-high reflectivity coatings on both mirrors. Original Skywacher primary mirror, original secondary replaced by a 44mm semi-major diameter unit from Orion Optics, UK. 22 per cent central obstruction. Now retired to garden.

           

          Plotina:

          Plotina: 130mm f/5 Newtonian reflector.

          130mm f/5 Newtonian reflector, with ultra-high reflectivity coatings, secondary mirror replaced by a slightly smaller (26.9 per cent central obstruction) by Orion Optics UK. Most frequently used grab ‘n’ go telescope.

           

          Tiberius:

          Tiberius: 5″ f/12 neoclassical achromat refractor.

          5″ f/12 IStar sourced neo-classical refractor with R 30 objective. Subject of much former work. Now retired to garden.

           

          Gaius:

          Gaius, my 80mm f/5 short tube achromat.

          80mm f/5 ShortTube achromatic refractor. Skywatcher objective in Opticstar tube assembly. This is the subject telescope of a new book dedicated to the ShortTube 80.

           

          The Traveler:

          The AstroPhysics Traveler; 80mm f/11 doublet achromat.

          80mm f/11 Astrophysics labelled achromatic refractor. Orginally donated to local school but returned to me after it was found in a sad state of neglected use. School instrument replaced by a smaller, shockproof instrument. Now seeking a new home.

           

          Achromatic Binoculars:

          9 x 28mm roof prism Pentax DCF LV pocket binocular (2009 vintage).

          The Pentax DCF 9 x 28mm LV pocket binocular.

           

          8 x 42mm Barr & Stroud Savannah roof prism  super wide angle. Most used, general purpose binocular.

          The Barr & Stroud 8 x 42 wide-angle binocular

           

          10 x 50mm Barr & Stroud Sierra roof prism. General purpose, astronomy binocular.

          The Barr & Stroud 10 x 50 roof prism binocular.

           

          Pentax PCF 20 x 60 WP II: Large porro prism instrument, used on a monopod for specialised deep sky observing/solar viewing.

          Pentax 20 x 60 PCF WP II porro prism binocular.

           

          Future plans: converting my two Newtonian telescopes in active use to binoviewing mode. Currently investigating options.

           

          De Fideli.