New Book: “Upgrading a Budget Newtonian Reflector.”

Battle o’ the Specula; 180mm f/15 Maksutov versus 204mm f/6 Newtonian. The latter proved superior in field experience.

Preamble

Dear Readers,

I am now working on a new and exciting book for amateur astronomers everywhere. It’s entitled, Upgrading a Budget Newtonian Reflector, and, as its name implies, it will be aimed at empowering amateurs on restricted budgets to get the most out of their econo-Newtonian reflectors that are now available in a wide range of apertures from just 3 inches up to 20 inches and more.

The book has been a long time in coming. Though I’ve written a book surveying the Dobsonian telescope market some years ago now, it was written with little or no sustained interest in these particular instruments, and, as such, became more of a buyer’s guide than anything else. Some ten years ago, I was heavily committed to endorsing small refracting telescopes, having owned, used and written copious volumes on several dozen models personally tested in the field, and through many published reviews in magazines like Astronomy Now.

My book from 2012.

But as I learned more about the people who exclusively endorsed refractors (as I once did), I discovered a very nasty side to the hobby. More often than not, their owners were more interested in talking about their telescopes rather than looking through them! You don’t have to delve deep into the world of refractors before you discover this materialistic streak. Copious online threads designed to draw attention to large and very expensive refractor telescopes have led many unsuspecting individuals to believe that there is something altogether magical about them. And it took me quite some time to shatter this illusory perception.

Giving honest assessments of optical performance in the field; a CFF 160mm f/8 apochromat (left) versus a modified 204mm f/6 Newtonian. The results were surprisingly close!

You see, I’m a Newtonian convert. It wasn’t an overnight conversion though, but one reached after climbing a steep learning curve, as I slowly acquired the necessary skills to properly adjust, upgrade, acclimate and deploy various Newtonians in the field. That said, It’s neither a revolutionary or a heretical statement; I mean the ABCs of optics – or at least the optics I had learned at school – teach us that larger apertures collect more light to see fainter objects as well as delineating finer details. And the laws of economics show us that Newtonians provide the easiest route to getting the best of both worlds.  Indeed, as I now firmly believe, having amounted considerable evidence in defence of this hypothesis from both the archives and first-hand experience, refractors are predominantly beginners’ telescopes, chosen because they are just that; small and charming – requiring little or no maintenance, and owing to their restrictive apertures, quite often perform near their theoretical limits. Indeed, these are the main reasons I continue to recommend small refractors to newbies. But to see more of the Universe you must scale up; and that’s something refractors just ain’t good at. That’s one of the main reasons hardly anyone would consider a refracting telescope larger than six inches(150mm) in aperture just for visual use, owing to their considerable cost, the unwieldiness of their long tubes, not to mention their heavy(read expensive) mounting requirements and sheer impracticality(apart from showing off) for visual use.

Newtonian telescopes are a breath of fresh air in comparison, with plenty of charm to boot, and I saved enormous amounts of money as a consequence! I discovered that one of the main reasons amateurs don’t stick with them is their temperamental nature. Bad collimation, inadequate acclimation and considerable ignorance concerning how to assess local atmospheric conditions, have given far too many amateurs pause to assessing Newtonian reflectors fairly. Indeed, this is not merely a modern phenomenon; the rich archives of historical astronomy proved to me once and for all that Newtonians were used to great effect by some of the best visual astronomers in history, who realised, then as now, that they offer by far the best bang for buck of all telescope types and deliver the readies! And not only that, Newtonian reflectors proved excellent in fields of amateur astronomy traditionally associated far more with refactors and catadioptrics; take double star observing as a prime example!

This book will therefore begin by explaining, in some considerable detail, my reasons for switching to Newtonian reflectors, having previously enjoyed all manner of other types of telescopes, including refractors and catadioptrics over the years and decades. Part of the reason for this is the marked improvement of mass-market mirror quality in recent years, where Synta/GSO are now routinely churning out primary mirrors with 1/5 or 1/6 wave PV figures, which are well above the run-of-the-mill ¼ wave (diffraction limited) or worse standard once offered. Sadly, it is often the secondary mirrors that leave a lot to be desired in these economically priced telescopes, so I will discuss what the amateur on a budget can do to upgrade these fairly cheaply to get more or less instant improvements in image quality.

Structure of the Book

The book is to be divided into two parts. Part I will consist of about 60 per cent of the text and part II will cover the remaining 40 per cent. Total length: ~200-300 pages(US English). The book will feature three Newtonian telescopes in detail:

A 130mm F/5 Newtonian (SkyWatcher primary) on an alt-azimuth mount

A 204mm f/6 Dobsonian (SkyWatcher primary)

A 305mm f/5 Dobsonian(GSO primary & secondary)

 

Part I: Projects to Improve the Performance of Budget Newtonian Telescopes

Chapter 1: A Tale of Three Inexpensive Telescopes: In this introductory chapter, I describe the acquisition of three inexpensive Newtonian telescopes, manufactured by Sky Watcher and GSO. I discuss the traditional advantages and disadvantages of Newtonians over other telescope types, followed by my initial assessment of their performance(star tests etc), describing both the telescopes, their mounting arrangements and supplied accessories, as well as my initial thoughts on their potential to be improved and a plan of action for making those upgrades.

Chapter 2: Improving the Optics: This chapter will outline in considerable detail how the optics on the three Newtonians were improved. Looking at the primary and secondary mirrors, I describe how I had the mirrors re-aluminized using state-of-the-art coatings that improve reflectivity, reduce scatter, increase contrast and durability. I show fellow amateurs how to accurately center spot their primaries and look at the importance of optimizing the central obstruction of the secondary mirror for visual use, and upgrading the secondaries with smaller, flatter mirrors delivering noticeable improvements in the quality of the images. I also consider other options available to me, discussing what the market offers amateurs on a tight budget, showcasing companies/services offered in Europe and North America. Is it more prudent to buy-in higher quality primary mirrors or to proceed with the existing primaries if their figure is found to be ‘satisfactory’ or’ good’ but nothing especially notable to write home about? I argue in the negative, as the effects of an up-graded secondary mirror are taken into account

Spring cleaning.

Chapter 3: Aligning the Optical Train: Newtonian reflectors are capable of serving up very high-quality images of high-resolution targets only if the optics are properly aligned. Accordingly, this chapter will take a detailed look at how aligning the components of the optical train can be achieved using a variety of techniques including simple naked eye assessments with low-tech collimation caps etc, followed by a detailed look at the strengths and weaknesses of using a quality Cheshire collimation eyepiece. From there I proceed to looking at high-tech approaches to collimation using a variety of laser collimators, outlining their strengths and weaknesses(the inaccuracy of cheaper laser collimators, for example), as well as describing the operation of some of the best available gadgets( e.g. Howie Glatter, Barlowed laser methods and Hotech SCA laser collimators) to achieve highly accurate alignment of the optical train in a matter of seconds.

Chapter 4: Improving the Housing of the Telescopes: In this chapter, I describe how to improve the housing of the optical train using flocking material to minimize stray light, internal reflections and image contrast. I also describe how the thermal properties of the tubes can be improved using traditional materials like cork to reduce tube currents and other bugs normally encountered by Newtonian telescopes during their acclimation and during temperature fluctuations that occur in the field. I will also consider the advantages of upgrading the generic focusers on some of these telescopes in order to improve focusing smoothness and precision.I will also include a short discussion on telescope maintenance; including cleaning the optics and the best ways to store the instruments when not in use.

Chapter 5: Mounting Considerations: In this chapter, I consider ways to improve the mounts of three telescopes (5.1 inch, 8-inch and 12-inch), looking individually at each. The 5.1 inch was supplied with a simple, table-top lazy Suzan alt-azimuth but was re-mounted on a much more functional and stable Vixen Porta II mount. I describe low-tech upgrades to the existing plywood lazy Suzan Dob mounts using an inexpensive garden water butt,  which both elevates the instrument (in this case the 8 inch Dob) off the ground and improves the smoothness of tracking the telescope both in azimuth and altitude, especially for high-power ‘push-to’ work. This is followed by a description of how one can improve the smoothness of motions in a budget Dob mount(using nylon strips, soaping surfaces etc) as well as balancing and pivoting considerations to improve balance in routine field use.

Chapter 6: Upgrading Accessories with Newtonians: In this chapter, I wish to explore how to upgrade the basic accessories supplied with these budget telescope packages, including eyepiece selection(how to choose eyepieces based on the different f ratios of the instruments under consideration(f/5 and f/6) ), Barlow lenses, finderscope upgrades and the use of dew shields etc.

A few skilfully chosen eyepieces and a Barlow lens are all you need to enjoy fine Newtonian images.

Chapter 7: Acclimation Considerations: No matter how good the optics on a Newtonian telescope, it will not deliver its best possible views if it is not properly equilibrated to its environment. Accordingly, this chapter takes a close look at how best to acclimate these telescopes. I consider passive cooling, simple, air-blown fans to scrub the boundary layer from the primary mirrors, as well as considering natural ways to cool down Newtonian telescope optics, e.g. by using wind to act as a natural fan to cool down the primary mirror, tactics to minimize or even eliminate cool down time by housing the instruments in a dry-unheated outhouse, where it can be immediately employed for high power observing, as well as observing strategies that largely avoid acclimation issues altogether, e.g. by starting with low power, wide-field viewing, that is less critical to thermally-induced aberrations, before moving on to medium and finally high power applications later in an given observing session.

 

Part II: Assessing Performance

Chapter 8: Lunar, Solar & Planetary Performance: Properly collimated and acclimated Newtonian telescopes with good optics are capable of generating truly breathtaking views of the Moon and bright planets. I discuss the performance of the three telescopes discussed in part I, which will include details of magnification regimes employed, resolution tests(craterlet counting on the floor of the lunar crater, Plato), the importance of good seeing conditions to obtaining the best high power views, which instruments are better or less suited to work on a given subject, use of color, Tele Vue planetary filters, polarizing filters etc,  and making sketches of the Moon and planets as well as other projects like accurately measuring the CM II longitude of Jupiter’s Great Red Spot to monitor changes in its size and position as a function of time. The chapter will also survey the kinds of solar viewing possible with a small Newtonian, including home-made full-aperture solar filters, and using inexpensive Wratten and interference-based filters to enhance views of sunspot morphology on the solar photosphere.

Octavius, the author’s dream telescope; a modified 8 inch F/6 Newtonian.

Chapter 9: Exploring the Deep Sky: The tremendous light-gathering power of medium-sized and large Newtonian telescopes makes them ideal instruments for exploring the deep sky, so this chapter will be describe what can be realistically expected form using upgraded optics( light gathering, resolution etc) on a suite of celestial objects, including star clusters, galaxies and other types of nebulae and the advantages and disadvantages of using nebular filters in the pursuit of certain types of objects(emission and planetary nebulae etc).

Chapter 10: Exploring Double Stars: In this chapter I will be detailing my results with these telescopes on a wide variety of double and multiple stars of varying degrees of difficulty in relation to well-established resolution parameters, and, in particular, the Dawes Limit. The chapter will also explore beautiful color-contrast pairs as they appear season-by-season, as well as ferreting out sub-arcsecond pairs when conditions allow.

Duodecim: the author’s 12″ f/5 Newtonian, used to validate the Taylor Hypothesis.

Chapter 11: Using a Small Newtonian as a Terrestrial Spotting ‘Scope: Traditionally small refracting telescopes are used to view subjects during the day. In this chapter, I outline ways to use a small 130mm f/5 Newtonian on an alt-azimuth mount with slow motion controls to obtain correctly-orientated terrestrial views that are sharp, contrasty and free of chromatic aberration. I show the reader what optical accoutrements can now be purchased that flip the optics from up-side down and right-left-flipped to upright and correctly orientated left-right images. I also outline the considerable advantages of using a larger aperture instrument such as this in low light/ dusk, dawn viewing of wildlife, considering concepts such as the twilight factor etc.

Using a Newtonian in terrestrial mode.

Chapter 12: Travelling with a Newtonian Telescope: A detailed narrative of how I have used the small, 130mm instrument successfully all over the British Isles, choosing a travel case, equipment to bring on the road etc, where it has delivered excellent results on a wide variety of targets from the Moon and the planets to galaxies, double stars and a host of deep sky objects. The chapter will recount results from results all over Scotland, England, Wales and southern Ireland.

Recounting many tales of life on the road with my portable 130mm f/5 Newtonian. The instrument is shown here at a friend’s home overlooking Cobh, County Cork, Ireland.

Index & Bibliography

 

To be continued…………………

 

De Fideli.

 

What I’m Reading(and re-reading).

Why one should never formulate a theology based on junk science.

 

Title: Theistic Evolution: A Scientific, Philosophical and Theological Critique

General Editors: J.P Moreland, Stephen C. Meyer, Christopher Shaw, Ann K. Gauger and Wayne Grudem.

Publisher: Crossway (2017)

ISBN: 13-978-1-4335-5286-1

Hardback, 1007 pages

US Price: $42.99

UK Price: £32.49

 

Many prominent Christians insist that the church must yield to contemporary evolutionary theory and therefore modify traditional biblical ideas about the creation of life. They argue that God used―albeit in an undetectable way―evolutionary mechanisms to produce all forms of life. Featuring two dozen highly credentialed scientists, philosophers, and theologians from Europe and North America, this volume contests this proposal, documenting evidential, logical, and theological problems with theistic evolution―making it the most comprehensive critique of theistic evolution yet produced.

 

“This volume fills a wide and expanding gap for Christians who continue to struggle with the relationship of evangelical Christianity to the claims of science. Specifically, for those who have rightly rejected the claims of unguided evolution, this book takes on the similar challenge of the possibility of theistic evolution. Scholarly, informative, well-researched, and well-argued, this will be the best place to begin to ferret out reasons for conflict among Christians who take science seriously. I highly recommend this resource.”
―K. Scott Oliphint, Professor of Apologetics and Systematic Theology and Dean of Faculty, Westminster Theological Seminary

Theistic evolution means different things to different people. This book carefully identifies, and thoroughly debunks, an insidious, all-too-commonly accepted sense of the phrase even among Christians: that there is no physical reason to suspect life was designed, and that evolution proceeded in the unguided, unplanned manner Darwin himself championed.”
―Michael J. Behe, Professor of Biological Sciences, Lehigh University; author, Darwin’s Black Box and The Edge of Evolution

“Evangelicals are experiencing unprecedented pressure to make peace with the Darwinian theory of evolution, and increasing numbers are waving the white flag. The tragic irony is that evolutionary theory is more beleaguered than ever in the face of multiplying scientific challenges and growing dissent. Until now there has been no consolidated scholarly response to theistic evolution that combines scientific, philosophical, and theological critiques. I was excited to hear about this ambitious project, but the final book has exceeded my expectations. The editors have assembled an impressive cast of experts and the content is top-notch. Theistic evolutionists, and those swayed by their arguments, owe it to themselves to read and digest this compendium of essays. This book is timely and necessary―quite literally a godsend.”
―James N. Anderson, Professor of Theology and Philosophy, Reformed Theological Seminary, Charlotte

“Repeating the error of medieval Christianity, theistic evolution absolutizes the words of finite, fallible humans and relativizes the Word of an infinite, infallible God. As this tremendous and timely collection thoroughly demonstrates, scientific stagnation, circular philosophy, and heterodox theology are the inevitable results. This is simply the best critique of theistic evolution available.”
―Angus Menuge, Chair of Philosophy, Concordia University Wisconsin; President, Evangelical Philosophical Society; author, Agents Under Fire: Materialism and the Rationality of Science

“This significant book persuasively argues that theistic evolution fails as a theory―scientifically, philosophically, and biblically. And with its broad-ranging collection of essays, it mounts a very impressive case. Strongly recommended, both for those who seek to defend Christianity intelligently and for those who find Christianity implausible because of the claims of neo-Darwinism.”
―Michael Reeves, President and Professor of Theology, Union School of Theology, Oxford, United Kingdom

“The theistic evolution solution to the creation-evolution controversy herein encounters a substantial, sustained, and trenchant critique. The team of scientific, philosophical, and theological scholars assembled by the editors have joined to confront the venerable theory with a stinging challenge that its adherents will have to answer if they value their scholarly integrity. This is necessary reading for those who wrestle with the great questions surrounding the origins of life.”
―Peter A. Lillback, President, Westminster Theological Seminary

“This landmark achievement contains an amazing collection of chapters by a powerful group of fully qualified experts in molecular biology, mathematics, philosophy, and theology. The chapters are clear, detailed in addressing all aspects of theistic evolution, and of a tone in keeping with 1 Peter 3:15: ‘with gentleness and respect.’ I consider this a must-have book for any Christian who wants to be able to give compelling answers to others who believe in theistic evolution.”
―Richard A. Carhart, Professor Emeritus of Physics, University of Illinois at Chicago

“This book offers a much-needed, comprehensive critique of evolutionary creationism (theistic evolution), covering its scientific, philosophical, theological, and biblical deficiencies. It devotes much space in particular to the scientific side. This focus is needed because of the common, unwarranted assumption that Darwinism is doing well as measured by scientific evidence. Several articles, from different angles, show how much Darwinism depends on seeing all biological evidence through the lens of a prior commitment to faith in the philosophy of naturalism―particularly the ungrounded assumption that unguided natural forces must suffice as a complete account of origins.”
―Vern S. Poythress, Professor of New Testament Interpretation, Westminster Theological Seminary

“‘In wisdom you have made them all,’ says the psalmist of God’s activities in nature (Ps. 104:24). But believers today, often blinded by modern science, fail to see that divine wisdom. This valuable volume challenges the assumptions of much scientific endeavor and proposes a fresh paradigm that is open to God’s involvement in nature. It deserves a wide and thoughtful readership.”
―Gordon Wenham, Emeritus Professor of Old Testament, University of Gloucestershire, United Kingdom

“Few scholars even marginally knowledgeable regarding the nature of this debate could read objectively the lineup of scholars in this volume and not be impressed. Beyond the scholars’ academic credentials, the topics covered are both sophisticated and timely. For this reviewer, the experience caused me to respond time and again: ‘I want to start right there . . . or maybe there . . . wow―have to read that one first . . .’ The topic is not always an easy target, but after almost one thousand pages of critique across interdisciplinary lines, I do not think that it could be bettered. Kudos! Highly recommended.”
―Gary R. Habermas, Distinguished Research Professor and Chair, Department of Philosophy, Liberty University

“As the debate over the origins of the universe, earth, and humans continues, and Christians grapple to understand the relationship between science and Scripture, evolution and creation, the voices in this book need to be heard. Scientific data need not be in opposition to what the Bible teaches about God and his world. The big questions about life are simply beyond the reach of ‘objective’ analysis. This volume critiques theologically and philosophically the flaws of positions that marginalize God from the process.”
―James Hoffmeier, Professor of Old Testament and Ancient Near Eastern History and Archaeology, Trinity Evangelical Divinity School

Theistic Evolution is a carefully crafted, academically sophisticated interdisciplinary challenge to the attempt to wed Christian theism to any version of the Darwinian project. I am awed by its scope and by the magnificent success of its intentions. Whether your interest is in the scientific deficiencies, the philosophical failings, or the theological dangers of Darwinism hitched to theism, look no further than this thorough analysis. Theistic Evolution is simply the most comprehensive and convincing critique of the topic I’ve ever read―a singular resource for careful thinkers―replacing a dozen books on my shelf.”
―Gregory Koukl, President, Stand to Reason; author, The Story of Reality and Tactics

“An increasing number of evangelicals are advocating theistic evolution as the best explanation of human origins, thereby denying the special creation of a historical Adam. Without taking any specific view as to the age to the earth, this important new book demonstrates that theistic evolution fails to take proper account of Genesis 1–3 as a historical narrative. Leading scholars from a variety of academic disciplines argue that theistic evolution is exegetically ill-founded, theologically damaging, scientifically implausible, and philosophically unjustifiable. Written with an irenic tone toward those it critiques, this book will help guard against false teaching in the church that undermines the gospel and will also provide apologetic help for confident evangelism in a secular world.”
―John Stevens, National Director, The Fellowship of Independent Evangelical Churches

“With the ‘death of God’ and the ‘hermeneutics of suspicion’ having captured the academy decades ago, the apologetic discussion moved decisively to the nature and origin of human beings. With this volume, the editors and contributors to Theistic Evolution have given us an important and much-needed resource for the conversation currently taking place within evangelicalism. Comprehensive in its breadth, specific in its critique, and confidently nuanced in its tone, each chapter contributes to a thorough rebuttal of the idea that theistic evolution is compatible with either historic Christian faith, sound reasoning, or rigorous science. But while written by specialists, Theistic Evolution is remarkably approachable to the average reader. I highly recommend this volume to students, pastors, educators, and anyone else who cares deeply about the discussion of human origins. This is a major contribution to one of the most important debates of our time.”
―Michael Lawrence, Senior Pastor, Hinson Baptist Church, Portland, Oregon; author, Biblical Theology in the Life of the Church

“Under the banner of ‘theistic evolution,’ a growing number of Christians maintain that God used evolution as his method for creation. This I believe to be the worst of all possibilities. It is one thing to believe in evolution; it is quite another to blame God for it. Indeed, theistic evolution is a contradiction in terms―like the phrase “flaming snowflakes.” God can no more direct an undirected process than he can create a square circle. Yet this is precisely what theistic evolution presupposes. Modern Christians too often buy high and sell low―just as neo-Darwinian evolutionism is fighting for its very life, it is being propped up by an irrational hypothesis. Theistic Evolution is the most thorough and incisive refutation of this dangerous presupposition. I strongly recommend this volume!”
―Hank Hanegraaff, President, Christian Research Institute; Host, Bible Answer Man broadcast

“This volume is the most comprehensive study on the relation between evolution and Christian faith I have discovered so far. While opening up fascinating firsthand insights into cutting-edge scientific results, at the same time the book treats the reader to a bird’s-eye view, asking the fundamental philosophical and theological questions and delving into the underlying worldview assumptions. It provides a very substantial contribution to the ever-ongoing dispute between naturalism and Christian faith in the areas of philosophy, theology, and the sciences.”
―Alexander Fink, Director, Institute for Faith and Sciences, Marburg, Germany

“Essentially, theistic evolution says Charles Darwin and Richard Dawkins got the science right, but that God is still somehow involved. Putting this view into the crosshairs, this book argues convincingly that the science of evolution is in fact wrong, and that any theistic gloss one puts on it is thus doubly wrong.”
―William A. Dembski, Former Senior Fellow, Discovery Institute; author, Intelligent Design: The Bridge Between Science and TheologyThe Design Revolution; and Intelligent Design Uncensored

Theistic Evolution is a major contribution to the very lively debate of exactly how to understand the ‘data’ from God’s revelation of himself in his Word with the ‘data’ from his revelation of himself in his world. Previous contributions to this debate have generally focused on the data from either science or Scripture. Theistic Evolution benefits from its comprehensive analysis from theologians, philosophers, and scientists in the same book. Whatever are your current views, Theistic Evolution will provide analysis from some of the most prominent critics in this conversation that should be helpful to people on both sides of this debate.”
―Walter Bradley, Former Professor of Mechanical Engineering, Baylor University

“The question of origins rarely fails to attract interest, not least because it is overloaded with worldview implications. For too long the increasingly shaky modern ‘Darwinian’ synthesis has been accommodated into theological thinking. This remarkable book exposes how scientifically and philosophically preposterous the notion of theistic evolution really is. An authoritative and vital contribution to the topic!”
―David J. Galloway, President, Royal College of Physicians and Surgeons of Glasgow; Honorary Professor, College of Medical, Veterinary and Life Sciences, University of Glasgow

 

De Fideli

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

Octavius: when a ‘scope costing a few hundred pounds eats a £1500 refractor for breakfast, your telescopic worldview has to change……and it did!

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.

    I like using my 105mm APO on double stars over my larger scopes just because it gives nicer images even when the seeing is below average.  I still get nice round stars but the whole image kind of bounces almost like my clock drive is making it bump up and down a little.

    An 8″ scope will be affected 4 times as much as a 4″ on the same night, so in this case aperture doesn’t rule in below average seeing.

    If I am going specifically after doubles, I tend towards my 10 inch Dob rather than any of my refractors.  One reason is for it to perform it’s rock solid best, I need to set out up before sunset and run the fans for considerably more than an hour.

    If the seeing is on the good side and I started with a 4 or 5 inch, I’m stuck.  

    For closer doubles, maybe 1.4″ or closer, the 10 inch provides wider splits under most circumstances because it’s Airy disk is so much smaller. A 1.14″ double is a Dawes limit split in a 4 inch, in the 10 inch it’s a wide split and I’m not fighting both the large Airy disk and the seeing.

    I’m not sure about your factor of 4 in terms of the effect on the image. I am not looking so much for a pretty image, I’m looking for closer splits. Antares is usually a challenging split in a 4 or 5 inch but last year I made the split in my 22 inch with Antares quite low on the horizon, no way in a small scope.

    It wasn’t pretty but it was very wide, bright and apparent. It made me realize just how small the airy disks are in a scope that size.

    With any scope but a larger scope in particular, the outer seeing aberrated region can as an extended object while it surrounds the region where the airy disk is brighter. Cranking up the magnification can increase the contrast by dimming that outer region.

    Jon Isaac( San Diego, California, USA), from an online thread entitled Effects of Bad Seeing: Double Stars

    This was my second dark site session with my new telescope.

    A week before, I had to cut the session short as humidity became unbearable – spider and shroud started dripping.
    I want to share my impressions of this device now that I had a full session.

     

    Logistics first.
    This is not a small scope so I got a folding aluminum ramps for loading it. This way, I can load the scope alone and it is faster than loading my SW 12″ collapsible.
    just need to make sure that mirror box is tilted a bit so the bearing will not hit the car ceiling.

    FHh9hdim.jpg

    Truss and shroud are light and have plenty of room.
    For a 20″ monster, the process of loading is easy enough.
    If not totally lazy or must, the scope can be loaded/unloaded without ramps.

    The road to the dark site is about 2.5 hours drive. I have been making this trip every month for over a year now and love the drive.
    re4jgQFl.jpg jELqQBTl.jpg

    I was the first on site, about an hour before dark.
    Unloading was simple enough and once everything was out of the car, I went to assemble the scope

    Assembly is quick, Truss to mirror box, fasten the bolts, UTA on Truss, fasten the bolts and then the shroud.
    This takes few minutes and is easy, just as Ryan show in his Youtube channel.

    lIjKInHl.jpg 60bzIWYl.jpg

    For collimation I use the Farpoint 2″ collimation kit – laser and cheshire.
    Even after 2.5 hour drive, last part of it is off-road, collimation did not drifted by much.

    The entire process of assembly + collimation takes about ~20 minutes.
    With camp set – tent, table chairs, I still had time to dress for the cold before total darkness.

    I was lucky to see the gathering of Venus, Moon and Jupiter with Saturn watching from above.

    That was an amazing sight!
    wrqf0Bjl.jpg

     

    Observations:

    First I revisit the Vail nebula.
    Eyepiece – Nagler 31mm filtered with O-III
    Started with the Western part of the nebula from the tip through Cy52 to its bottom part. The amount of details was insane.
    The Eestern part as equally stunning.

    The central part of the nebula was nicely visible.

    Tonight’s plan was to go through objects in Cassiopeia, Perseus, Andromeda, Orion and Ursa Major.

    Double cluster fits nicely into the FOV of the Nagler 31mm. Very sharp image.
    Raising magnification a bit, still could see both clusters within view.
    Next came the Owl cluster, M103, NGC 663 and more.
    Pacman nebula was also nicely visible, I will have to revisit this object to figure out more details.

    I did a quick detour to view M15. This cluster is magnificent! raised magnification to 135 and the cluster could be resolved nicely.
    With magnification of over x200 which is reserved for such objects, I could easily distinguish stars almost to the core.

    Andromeda Galaxy showed two dust lanes, one very distinct and the other is fainter. I never saw so many details in the arms before.
    Both companions – M110 and M32 also fit the FOV.

    Pinwheel Galaxy, another showpiece object also provided much details.

    In Orion, I saw the bubble nebula for the first time.
    M42 is majestic as ever, all the details are just fantastic, the nebula is closing full circle, wings full of details. With filters, different details emerge.

    The 20″ collects so much light that even a cellphone camera could yield details (I had to try…)
    Eh3jJUPl.jpg

    Horsehead nebula was not visible when it was 30-40 degrees but when reaching over 50 degrees altitude, provided a lots of details.
    The nebulusity from Alnitak towards HD 37806 was visible with the horse interrupting it like a finger obscuring the view.

    Last area covered was Ursa Major – galaxy hunting.
    Finding galaxies with this huge field of view is fun and easy.

    This session yielded many objects, over 50 were documented, many were not viewed enough and will be revisited to get more details.

    My impressions so far:

    I am very happy with my new telescope.
    The difference in view from my 12″ is everything I expected and more, some objects are actually visible and others show so much more details.

    Views are wide, crisp and sharp, especially when conditions allows.
    Transportability and the ability to handle it by myself is exactly why I opted for NMT in the first place.
    Mechanically this is a wonderfully constructed device. Movement is smooth in both axis but firm enough not to shift when switching eyepieces.
    Balance is the same without eyepiece or with Paracorr-2 + Nagler 31mm. I guess Binoviewer will require some counterweight – Ryan provided rails for counterweight, just in case.
    Collimation lasts in full movement range and during the session – I did not check, but felt no view degradation – will test it on the next session.

    Scope Basking in the morning sun after a long night
    AL5Ge1Al.jpg

    ilan Shapira( Israel), from an online thread entitled; My NMT 20″ f/3.3

    Got back out for an hour or so and tried out my higher powered plossls. Seeing was not great and I’m under white zone skies with limited sky to point at from my driveway but I make it work. I can tell the scope is a bump up from my ST80 with the higher powered eyepieces. To my newb eyes collimation appears good. Stars weren’t exactly pinpricks at high power but they’re round and turn into nice round donuts in and out of focus.

    Took a look at a dimming beetleguese, Uranus with I think a hint at its moons. The Pleiades looked great back down with the 32 plossl.

    M42 looked better than I’d ever seen it at all powers. And it looks spectacular to my eyes with my $13 UHC filter.

    It’s definitely a different experience looking through the eyepiece on this reflector as opposed to my mak and my refractor. Just a bit higher at most views than is perfect viewing on my camp stool, but being able to rotate the tube in the rings brings it to an accessable height.

    (If this post would have been more appropriate in the beginner forum I apologize.)

    Tannhauser Gate, from an online thread entitled, First Light with a cheap 130/650/f/5

    I like 130 mm F/5 Newtonians. If the optics are decent, they’re the closest thing to a budget 4 inch apo you can buy.

    The focuser appears to be a Crayford, that’s a good thing. It looks like a 2 inch Orion focuser,, there’s no adapter?

    Have fun..

    Jon Isaac( San Diego, California, USA), from an online thread entitled, First Light with a cheap 130/650/f/5

    Actually it goes a little deeper than any 4 inch Apo and resolves significantly closer double stars(down to 0.9″) in the hands of experienced observers and good seeing conditiions.

    Mr Hardglass

    That’s a sharp looking scope.,I love my 130.,it’s my most used scope because it puts up great views and is easy to carry out and be viewing.,cheers.

    Clearwaterdave,(Western Maine, USA), from an online thread entitled, First Light with a cheap 130/650/f/5.

     

    Attached Thumbnails

    • 20190327_183143.jpg

     

    Because seeing was good at Christmas I observed Sirius. In 2012 I had great difficulty to see the Pup, but now it was rather easy. I tried to make my pencil sketch as realistic as possible. I added some color in GIMP but I’m not 100% satisfied with the result.

    Which version do you prefer?

    Attached Thumbnails

    • Sirius B afgewerkt grijs 600.png

     

    Attached Thumbnails

    • Sirius B afgewerkt kleur 600.png
    Jef De Wit(Hove, Belgium), from an online thread entitled Sirius B (the Pup)

    I hope to have a 20″SST/Ostahowski f/3.4 in about 12 mo(nths).

    This summer I should have a unique 10″ NMT/Pegasus f/3.4 DOB

    I’ve owned a 12″ Orion dob that has been in pieces as I tried to repair the dead goto system.

    Got an AT130 f/7 that sits too much because, as a DOB lover, I hate equatorial mounts. Has some nice planet views, a super value no question. Just not a KILLER at f/7.

    Been thinking about a Sky-Watcher Skymax 180 f/15 but not many reviews here on CN.

    I’ve reached out to Moonraker about his 150 Mak in development, turns out he’s recovering from some illnesses and the Mak is new for him-gonna be awhile. Just love his work though.

    SO-back to the purpose- what do you suggest for a Planet Killer?

    Stubeeef(North Carolina), from an online thread entitled: Want a Planet killer: suggest some

    Get a cheap 10″ dob.

    Pull the mirror and send it off to a professional mirror refinisher and have them bring it up to a high Strehl level.

    Put a high quality secondary mirror in it.

    Put boundary layer cooling fans on it.

    Even an 8″ f/6 will work well for this, but the 10″ will be better.

    Eddgie, from an online thread entitled: Want a Planet killer: suggest some

    Eddgie, on 17 Jan 2020 – 03:42 AM, said:

    Get a cheap 10″ dob.

     

    Pull the mirror and send it off to a professional mirror refinisher and have them bring it up to a high Strehl level.

     

    Put a high quality secondary mirror in it.

     

    Put boundary layer cooling fans on it.

     

    Even an 8″ f/6 will work well for this, but the 10″ will be better.

     

     

    This ^

    SteveG( Seattle, Washington, USA), from an online thread entitled: Want a Planet killer: suggest some

    The slower the scope, the better. I had a Discovery 10 F5.6 that gave great planetary views, but it couldn’t compete with my 8” F9 when it came to high power views. With 3.5 mm and 5mm eyepieces, I can comfortably view objects at high power all night long. And not once have I ever observed a planet with my 8” and thought, the image isn’t bright enough. Barlows are useful with fast scopes, but a 2x barlow will not perform nearly as well as a scope with twice the F ratio.

    Galicapernistein, from an online thread entitled: Want a Planet killer: suggest some

    bobhen, on 17 Jan 2020 – 1:40 PM, said:

    It’s all about the quality of the primary. Whether its F5 or F8 doesn’t matter. If the mirror is 1/10 wave it is 1/10 wave.

     

     

    I think closer to 1/8 limit

    But it has to be real. Regardless of the manufacturer and its advertising promotion.

    a  I, from an online thread entitled: Want a Planet killer: suggest some

    I would think a 20″ Ostahowski f/3.4 would be a fine instrument for planetary observation once cooled and well collimated… 20″ of well figured aperture would pretty much kill anything you throw at it.

    Volvonium(Long Beach, California, USA), from an online thread entitled: Want a Planet killer: suggest some

    Not really sure what to suggest but my 25″ kicks butt on the moon and planets. Barring going for such a big scope my 8″ f/9 Parks newt on a platform is a close second.

    Keith Rivich(Cypress, Texas, USA), from an online thread entitled: Want a Planet killer: suggest some

    I have an f/4.5 16” Ostahowski mirror, and also an 8” f/7 by Steve Lee. Both appear excellent mirrors but the 16” slam dunks the 8” on everything. As it should. Every time I think of building a planet killer…like, say, a 10” f/7 or whatever, I remind myself I already have one.

    Oberon(Hunter Valley, NSW, Australia), from an online thread entitled, Want a Planet killer: suggest some

    I have a 6-inch F/8 that is a planet killer for a small telescope, but the 8-inch SCT, 10-inch F/4.5 an 15-inch F/4.5 Dobs also do very well on the planets too when the seeing is good. I spent many hours looking at Mars, Jupiter and Saturn with my reflecting telescopes, and imaging them with the 8-inch SCT. The best views though came with my Dobs though, especially the 15-inch. That said, the 6-inch is no slouch and has excellent optics, the primary mirror was made by Meade back in the 70’s. The 10-inch also has a Terry Ostahowski mirror, and the 15-inch has a primary mirror made by Optic Wave Labs.

    Achernar(Alabama, USA), from an online thread entitled, Want a Planet killer: suggest some

    A well figured 10″ as has been mentioned. Some of my best views of Mars were with a 10 f/5.4. Saw dark volcanoes on Mars years ago with 8″ f/7. Mars was high up, seeing was spectacular and scope was working well at 600x. My eyes were a bit better, too.

    Mike Spooner

    Any well built Newt is a brute for planets in my super steady seeing. Fast or slow is fine. Old school 8″ F/8 Cave or other makes also make great planet scopes as well as used Starmaster Dobs at around F/4.3.

    CHASLX200(Tampa, Florida, USA), from an online thread entitled, Want a Planet killer: suggest some

    On nights of fair to average seeing, I will be relying on my TSA 120; on good to excellent nights it will be my new-to-me Teeter- Zambuto 10” f/5. It was damaged in shipping is still in limbo awaiting settlement from the shipper.

    Skyranger(Prescott, Arizona, USA), from an online thread entitled, Want a Planet killer: suggest some

    Custom designed Newton:

    Obstruction less than 20% = planet killer or APO killer

    Cameras for planets: ASI / QHY – 290 / 224 = 6 – 7 mm diagonal.

     

    Newton 12″ F/5.3  (300×1600)
    Primary Mirror: 303 mm
    Secondary Mirror: 50 mm
    Obstruction: 16.5% (Obstruction surface: 2.72%)
    Illuminated diagonal: approx 9-10 mm

     

    Newton 12″ F/5  (300×1500)
    Primary Mirror: 303 mm
    Secondary Mirror: 50 mm
    Obstruction: 16.5% (Obstruction surface: 2.72%)
    Illuminated diagonal: approx 7-8 mm

     

    Newton 10″ F/6.4 (250×1600)

    Primary Mirror: 254 mm
    Secondary Mirror: 40 mm
    Obstruction: 15.7% (Obstruction surface: 2.48%)
    Illuminated diagonal: approx 10-11 mm

     

    Newton 10″ F/6 (250×1500)
    Primary Mirror: 254 mm
    Secondary Mirror: 40 mm
    Obstruction: 15.7% (Obstruction surface: 2.48%)
    Illuminated diagonal: approx 8-9 mm

     

    Newton 10″ F/5 (250×1250)
    Primary Mirror: 254 mm
    Secondary Mirror: 45 mm
    Obstruction: 17.7% (Obstruction surface: 3.14%)
    Illuminated diagonal: approx 7-8 mm

     

    You can do the calculations on this website:

     

    https://stellafane.o…b/newt-web.html

    cabfl, from an online thread entitled, Want a Planet killer: suggest some

    My 8″ f/8. Royce primary, Protostar quartz secondary. After midnight, when the seeing settles and the scope temperature has fully equalized.

    K15CAW, from an online thread entitled, Want a Planet killer: suggest some

    I had a 6” F8 Discovery dob that had an excellent mirror. But my SW 100 ED was close enough that I sold the dob for the convenience of the refractor. But going from a 6” F8 to an 8” F8 or 9 dob puts you into an entirely different league. I would put my 8” F9 against any 5” APO refractor. That said, I still want a 5” APO refractor.

    Galicapernsitein, from an online thread entitled, Want a Planet killer: suggest some

    obhen, on 17 Jan 2020 – 7:38 PM, said:

    No place in the United Sates will a 20-inch telescope ever resolve to its full potential.

     

    On few nights and in the best locations like south FL. a 12 to 16-inch will have a chance but in most locations just getting sub arcsecond seeing is rare. And not only do you need that seeing but the planets need to be high or at zenith or the seeing will be compromised even more.

     

    For example…
    “At the William Herschel Telescope site in the Canary Islands, even this superb viewing location (second best in the northern Hemisphere) has many nights of relatively poor seeing: the distribution is positively skewed, and at this excellent site, a 10-inch telescope will be seeing limited on 9 out of 10 nights.”

     

    Bob

     

    That’s really not the question. A large scope maybe seeing limited but still outperform a smaller scope. 

     

    The Dawes limit and the Rayleigh criterion are not the appropriate measures to determine the resolution/ seeing limits. 

     

    In 1 arc-second seeing, a 10 inch will be seeing limited but dramatically out perform a 5 inch. 

     

    Think about airy disk diameters and overlapping disks.. 

     

    This my planet killer..

     

    IMG_18102019_213052_(1080_x_1080_pixel).jpg
    13.1 inch F/5.5 with a Royce mirror.  
    The 16 inch and the 22 inch could be but are permanently located in the high desert where the seeing is not as good as it is near the coast.
    Jon Isaac(SanDiego, California, USA), from an online thread entitled, Want a Planet killer: suggest some

    The best planet killer is the atmosphere.

    A scope also needs to be thermally stable and well collimated, as well. There are better scopes out there, of course, so get one. But prepping a scope for planet killing is probably the most important factor outside of seeing conditions and recognizing planetary detail when we see it.

    Asbytec(Pampanga, PI), from an online thread entitled, Want a Planet killer: suggest some

    I’d say something in the 10-12″ f/5.5 + range with good optics and proper cooling.

    jakecru(Nevada, USA), from an online thread entitled, Want a Planet killer: suggest some

    I have an 8″ f/8 dob that is GREAT on the planets. Plus, it’s a lot of fun to use, too. Really has the “OK, so it’s come to this!” feeling when you aim it at anything. Ha! Something to keep in mind is binoviewers are excellent for planetary work, and will the scope/mount handle it. The dob does great with this, too.

    JoshUrban(Indian Head, MD, USA), from an online thread entitled, Want a Planet killer: suggest some

    Bill Jensen, on 19 Jan 2020 – 6:31 PM, said:

    Zambuto has an in stock 8 inch f/7 that is listed on his website. Those don’t come up that often, and may be a nice solution to your planetary viewing desires.

    This 

     

    I have a quartz Zambuto 8″ F/7 on order that should be ready in about a year or so. I would like to find a lightweight scope to house the mirror and then possibly put it on an equatorial platform. 

    starzonesteve(Central Alabama, USA), from an online thread entitled, Want a Planet killer: suggest some

    I got lucky on used parts on AM that included a Zambuto 8″ F7 quartz. It’ll clobber any 6″ refractor on the planets, and is basically up and running in a few minutes as the substrate doesn’t have temperature equilibration issues.

    The 8″ is so good that I’ve decided to replace my 12.5″ F5 Zambuto pyrex with one of his quartz mirrors. I’m hoping it’ll be ready in the summer.

    areyoukiddingme, from an online thread entitled, Want a Planet killer: suggest some

    CHASLX200, on 18 Jan 2020 – 12:11 AM, said:

    Any well built Newt is a brute for planets in my super steady seeing.  Fast or slow is fine.  Old school 8″ F/8 Cave or other makes also make great planet scopes as well as used Starmaster Dobs at around F/4.3.

     

    Most mass made Newts the last 20 years just don’t do it for me.

    +1  I have a 12.5” and an 18” Starmaster, both with Zambuto mirrors, and on the best nights they are planet destroyers.

    turtle86, from an online thread entitled, Want a Planet killer: suggest some

    Galicapernistein, on 21 Jan 2020 – 4:12 PM, said:

    A high F ratio is inherently better for high power views. A slow scope with excellent optics will give better views of planets than a fast scope with equivalent optics. This is a fact that owners of fast scopes need to accept.

    No, it is not a fact, and it is quite wrong, so we will not accept it.  What Jon said above is correct.

    The laws of optics and physics don’t lie – they will give the same view, assuming similar quality eyepieces and equilibration and the the eyepiece is designed for the faster cone, not including some miniscule effects (which are almost always overblown) from a larger secondary in the faster scope.  This is easily overcome by adding a small amount of aperture if one wishes.  Then the slightly larger fast scope wins.

    Let’s not ban certain terms, (i.e. planet killer) let’s educate people about where they came from and why they are misleading or wrong.

    My planetary scope?  My 20″ f/3.0.

    Mike Lockwood,from an online thread entitled, Want a Planet killer; suggest some

    Galicapernistein, on 21 Jan 2020 – 4:45 PM, said:

    So someone starting out in astronomy who wants to see Saturn’s rings should buy a 6 inch F5 because they’re so much more convenient than an F8? I don’t think so.

    Think outside the box.. 

    A 6 inch F/8 is 48 inches long, an 8 inch F/6 is 48 inches long, a 10 inch F/5 is 50 inches long.  They’re the standard dob configurations.. 

     

    I can tell you which one provides the better planetary views… 

    P.S.:  A 6 inch Newtonian is not what I consider a planet killer.  A good scope but not enough aperture.

    Jon Isaac ( SanDiego, California, USA), from an online thread entitled, Want a Planet killer; suggest some

    A slow scope will give better high power views than a fast scope with equivalent optics. It would be nice if we could accept that fact without bringing in these other factors.

     

    I accept that a slow scope with equivalent optics will provide slightly better views than a fast scope.  

    But it would be good if you would accept that those other factors are far more important in providing killer planetary views than the focal ratio.  

    Today, a slow scope that provides the planetary views possible with a large aperture, fast scope is impractical.  

    It is about the views.. 

    Jon Isaac (SanDiego, California, USA), from an online thread entitled, Want a Planet killer; suggest some

    I’ve gotten many extraordinary views of the moon/planets with an optically excellent 10″ f/5 dob. The whole idea of some longish newt or hyper-expensive APO as the only planets killers has one foot in mythology and the other in the grave.

    Largish aperture of high quality is your best bet.

    Nirvanix(Medicine Hat, Canada),  from an online thread entitled, Want a Planet killer; suggest some

    I own a 12.75” F/6 Newtonian with quartz optics that has killer specs and was figured by one of the best mirror makers in the US. On nights of best seeing it kills my TEC200ED, even at f/5.8. But on average nights it is another story entirely.

    Itha(Bend, Oregon, USA), from an online thread entitled, Want a Planet killer; suggest some

    cooke, on 24 Jan 2020 – 3:16 PM, said:

    I’m in the camp of thinking that a planet killer is any scope, regardless of f-ratio, type, or configuration, that has the capability of delivering a killer view of the planets.  As others have said, realizing that view has more involved than just the telescope itself; managing thermal issues, seeing, collimation, viewer experience, etc. all factor into what is seen but reducing the variables to just the telescope itself, it could be anything of sufficient aperture.  I do think that while smaller scopes can give excellent images of the planets for their size, if you don’t have at least 6″ of aperture and preferably 10″ of aperture, you are unable to realize the resolution available on the best of the best seeing nights.  Having said all that, my best views of Jupiter and Saturn ever were with a 18″F3.75 Starmaster.  I think the additional aperture also helps a lot when using high magnification to see the smallest lowest contrast details.  The additional light just helps make the difference even if the larger aperture is seeing limited.

    When I say a high F ratio is better for high power views, I should specify (and I will from now on) that I’m talking about smaller newts. Bigger mirrors can obviously compensate for many issues by sheer resolving power. An 18” F8 might provide better views, but the atmosphere will only allow so much power, and an 18” F8 would require a ladder I wouldn’t want to climb. The bigger exit pupils they provide are a definite improvement over smaller scopes. There’s no arguing that a big, fast newt packs a lot of performance into a relatively small package, and for serious galaxy hunting they can’t be beat. 

    Galicapernistein, from an online thread entitled, Want a Planet killer; suggest some

    scooke, on 24 Jan 2020 – 3:16 PM, said:

    I’m in the camp of thinking that a planet killer is any scope, regardless of f-ratio, type, or configuration, that has the capability of delivering a killer view of the planets.  As others have said, realizing that view has more involved than just the telescope itself; managing thermal issues, seeing, collimation, viewer experience, etc. all factor into what is seen but reducing the variables to just the telescope itself, it could be anything of sufficient aperture.  I do think that while smaller scopes can give excellent images of the planets for their size, if you don’t have at least 6″ of aperture and preferably 10″ of aperture, you are unable to realize the resolution available on the best of the best seeing nights.  Having said all that, my best views of Jupiter and Saturn ever were with a 18″F3.75 Starmaster.  I think the additional aperture also helps a lot when using high magnification to see the smallest lowest contrast details.  The additional light just helps make the difference even if the larger aperture is seeing limited.

    I agree. I have an AP 130 GT, and it’s as good as a 5″ apo can get. It certainly gives great planetary views, but it simply can’t compete with my 18″ Starmaster in terms of resolution, at least where I observe.

    turtle86, from an online thread entitled, Want a Planet killer; suggest some

    If i had to have one last planet scope, it would be a 20″ F/6 Dob.

    CHASLX200(Florida, USA), from an online thread entitled, Want a Planet killer; suggest some

    Newtonians of 8-12.5″ aperture are the most cost effective. I agree with others that perhaps the easiest/cheapest way to a planet killer is to buy a mass-manufactured Dob and have the primary refigured. First, though, you may want to replace the secondary with a high quality mirror from the likes of, say, Antares and see if you are happy. The MTF of any obstructed scope degrades significantly when the diameter of the secondary minor axis exceeds 20% the primary diameter. Thus, you will want such a small secondary, which if you also want a 1 deg or so field with only minor vignetting for DSOs, means f/4.5 or greater. So a 12.5″ with f/4.5 or greater can yield fabulous planetary detail. However, the mirror must be supported properly (check with the freeware program PLOP), the mirror must be allowed to thermally equilibrate (I set mine up at dusk … a fan is a good idea too), and collimation needs to be spot on. Incidentally, mass manufacture SCTs have central obscurations of roughly 35% so planetary contrast aperture-for-aperture is less than with a Newtonian.

    dhfergusson(Pleasanton, California, USA), from an online thread entitled, Want a Planet killer; suggest some

    Personally I use a 200mm F6 Quartz newtonian. I’d love to go bigger, but I also don’t like the idea of ever moving something bigger outside of my observatory, so for non-obs scopes, I keep them portable enough. I also do not like dob-bases due to the materials, I’d want it to be all metal. I’m in Florida. Florida is not friendly to non-metal and I’m not about to baby some cheap particle/ply or whatever cheap dobs are made of, and I’m not spending top dollar on a custom dob. I’d rather have a beefy alt-az and keep it simple and fast with the 8″ for now. Maybe one day I’ll get a metal dob frame and go 16″. But that’s a big maybe.

    MalVeauX(Florida, USA), from an online thread entitled Want a Planet killer; suggest some

    For me the #1 priority is an accurate figure – I’ve been satisfied with Newtonian planetary views from 6″ up to whatever. The primary is the building block at the bottom of the wobbly stack, IMHO. The secondary is next (and often a problem for critical viewing) but smaller sizes can be replaced with less hassle and financial impact than the primary. Most of the remaining problems fall into what I would classify as mechanical/environmental effects, i.e. thermal, collimation, seeing, mounting, etc.

    So pick a size, get the primary right and work from there. My personal opinion concerning f/ratio and secondary size is they can be considered for 6 to 8″ scopes as they are comfortable at f/10 or f/7 (for my height when Dob mounted). For larger scopes I like more comfortable f/ratios. With Paracorrs, modern eyepieces and collimation knowledge available having mitigated some of the old concerns, then we’re back to the quality of the objective – still the base of the wobbly stack for me.

    Mike Spooner, from an online thread entitled Want a Planet killer; suggest some

    Late to the discussion but here are mine, a TEC 200ED and my Parallax/Zambuto 11″ F7.  Rather than compete, they compliment each other.  

    Around here, the seeing rarely supports an 11″ aperture, so the TEC gets used more often.  When the seeing does support a larger aperture, I can get the Newt unbagged, the mount sync’ed and observing in under 10 minutes.  

    For me, planetary viewing demands exceptional optics (and seeing!!) but also a “comfortable’ viewing experience, which, again, for me, means being seated or standing comfortably.  I can do both with both scopes, making long sessions at the eyepiece a pleasure.

    Also for me, I’m just addicted too my bino-viewers, especially for solar system objects.   I just see more and I find the viewing experience much more comfortable than mono-vision, and with my Denk power switch system, I can cycle through three different magnifications instantly.

    For me, an excellent planetary newt has to have the following:

    1. 8″ – 12″ aperture and I prefer F6 or slower focal ratios

    2. Exceptional optics (including the secondary) that are smoooooth, with good coatings.

    3. Central obstruction under 20% (pretty easy to do really, especially in slow scopes)

    4. Excellent build quality which includes easy, precise collimation with the ability to keep collimation when pointed anywhere in the sky over the entire night and an excellent focuser.

    5. An excellent thermal management system, which typically includes a BL fan.

    6. Easy use of bino-viewers

    7. A rotating tube if I use a GEM, for easy, comfortable eyepiece positioning and the ability to put my body down wind of the aperture.

    Can’t wait for Mars this year!

    JeffB, from an online thread entitled Want a Planet killer; suggest some

    First light on my UVenus filter tonight!

    Attached Thumbnails

    Very nice photo. That’s a pretty awesome outcome for first light on any device.Thanks for sharing.

    I hope I’m not out of line in asking: Who is the manufacturer of your 8″ Newt and is the 3100mm your OT focal length?

    jodemur(East Michigan, USA), from an online thread entitled, Venus in UV – 8″ Newt + ASI183MM

    jodemur, on 26 Jan 2020 – 1:16 PM, said:

    Who is the manufacturer of your 8″ Newt and is the 3100mm your OT focal length?

     

    It is a Celestron Starhopper, one of the newer metal tube ones so a standard Synta product. They make pretty solid f/4.9 mirrors all the time so I figure f/6 should be even better. It’s a 1,200mm stock focal length but I measured the pixel width of Venus to calculate that my 2x Orion Shorty Barlow is giving me about 2.6x magnification.

    jragsdale(Idaho, USA), from an online thread entitled, Venus in UV – 8″ Newt + ASI183MM

    I was going to post in “what did you see with your classic ” but its large enough to be alone

    1 both scopes are in great shape

    2) both scopes mounted on lxd55 mount for better track

    3) seeing was very very good and moon was high up near zenith

    rv6 had 2x barlow

    ed4 some shots with 2x barlow and some not

     

    highfnum(North East, USA), from an online thread entitled, redo classic shootout edmund 4inch vs criterion RV6

    Cool images eh? Like I says in part I, I dinnae trust an over zealous sketcher, ken.

    Mr. Hardglass.

    so both scopes did a great job

    however RV6 does show more detail

    IMHO it looks like I picked up some of rille with ED4 – if correct that’s a new record for me for scope size

    ed4 had more trouble with smaller circular features

    some folks in past have said that a 4 inch refractor has same capability as 6 inch reflector

    if its a good 6 inch – I say no

    highfnum(North East, USA), from an online thread entitled, redo classic shootout edmund 4inch vs criterion RV6

    I purchased the Skywatcher 130mm PDS a few days ago. Shipping took about 4 days from the U.K. and was about 50 bucks. The diffraction pattern star test showed essentially identical in and out of focus diffraction patterns, a very nice optic. Here is an LRGB image of the globular cluster M15 taken last night.

    L=R=G=B= 125 seconds. Taken with a SBIG ST-402MM CCD.

     

    m15GC.jpg

    grafton(Houston, Texas, USA), from an online thread entitled, Skywatcher 130 f/5 PDS – mini review

    I tried out my Skywatcher 130 PDS on the moon a few weeks ago. A 3x barlow and an ASI120mm video camera was used. When I first received the scope a few months ago I did a star test and noted that the optics were very good.

     

    The crater Copernicus

     

    copernicus.jpg

     

     

    The crater Clavius

     

    clavius.jpg

    grafton(Houston, Texas, USA), from an online thread entitled, Skywatcher 130 f/5 PDS – mini review

    From my experience, a fast 12″ dob can have very good planetary images.

    “Killer” planetary is subjective I guess but my inclination would be to go for aperture, even from an urban observing location.

    Right now I don’t have a scope but I’m considering either a 10″ or 12″ dob which would be used mostly for lunar/planetary under city skies.

    My main issue is that I don’t like the tiny exit pupil that comes from using a small refractor at high power … but a 12″ newtonian is just cruising at x200.

    John Anderson, from an online thread entitled: Want a Planet killer-suggest some

    Mike Spooner, on 17 Jan 2020 – 11:41 PM, said:

    A well figured 10″ as has been mentioned. Some of my best views of Mars were with a 10 f/5.4. Saw dark volcanoes on Mars years ago with 8″ f/7. Mars was high up, seeing was spectacular and scope was working well at 600x. My eyes were a bit better, too.

     

    Mike Spooner

    Ask Mike if he has any planet killers for sale. I looked through his 6″ F10 a few years ago…OMG! Also, he has good seeing in the SW.

    Acocran(Sonora, California, USA), from an online thread entitled: Want a Planet killer-suggest some

    My killer would be a reflector, made by Ed Grissom, like the one found in ‘Best of reflectors thread’, ‘refractor vs reflector ‘, by Daniel Mounsey. Any size would probably be fine, but his 13″ sounds to be just about right !

    Subaru45(central Wyoming, USA), from an online thread entitled: Want a Planet killer-suggest some

     

    My AWB OneSky arrived today, but I didn’t think I’d get to use it anytime soon. For one thing, it was cloudy and rainy all day. For another, a civic organization I belong to had a meeting tonight. 

    But on the drive home from my meeting I realized that I could see stars. Still, I thought that by the time I got the scope unboxed and collimated the clouds would have rolled back in. But unboxing and collimating is better than watching TV. So I took the box into the dining room and started unpacking. 

    It took very little time to get the everything unpacked. Assembly was just mounting the red-dot finder. I put the collimating eyepiece in and noticed I could only see two of the three clips that hold in the main mirror. Went out to the garage to get the Allen wrenches. Lucky for me, the first one I turned moved things in the right direction. Loosen one, tighten the other two, and soon all three clips were visible. Then it was very quick work to get the main mirror lined up. Within 15 minutes of opening the box, I was ready to go.

    I took the scope outside through the garage. I could have sworn I had an empty five-gallon bucket in the garage, but I couldn’t find it, so I just set the scope on the driveway and sat down next to it. (Luckily the concrete was only slightly damp from the earlier rain.) I wanted an easy target to start with, so I lined up the red dot on the center of the moon and then looked in the low-power eyepiece. A quick turn of the focuser and… OMG that’s bright! I’m going to need a moon filter for sure! I spent a couple of minutes admiring the view, then I pointed at the middle star in Orion’s belt. I figured that would be a good check on the finder alignment. With the star centered in the viewfinder, the red dot was a bit high. I ran out of adjustment before I got it right on. I know in the OneSky thread there’s a fix for this, but the 25mm eyepiece covers such a wide area that it’s close enough for right now.

    Next stop: The Pleiades. They were like sparkling jewels on a piece of black velvet, and the wide field of view was amazing! This is such a different experience from my old 3″ refractor that it’s hard to find the words to describe it.

    Then the Orion nebula. Yep, found it in the center of the FOV and again, it was completely not like what I had seen through the DS-80. Time to call the wife outside. 

    I pointed it back at the Pleiades and she was suitably impressed. Then the moon, and she agreed that it was too bright to look at it for very long. Then I told her “let me show you one more thing. It’s kind of hard to see, but let’s take a look.” I told her to look at the sword hanging from Orion’s belt, and that I was going to point the scope at the star in the middle. I did, and she bent over to take a look. “It’s fuzzy.” I explained that it was a nebula, a cloud of gas illuminated by the stars in its center. Then she said “It’s green!” Wow. Her eyes are so much better than mine! I would never have thought that a 5″ scope under my suburban sky with a quarter-moon lighting things up would show color in the Orion nebula.

    By then the clouds had started to roll back in, so we packed up and came inside. I just can’t believe how great this little telescope is.

    GeraldBenton(Wilton, NC, USA), form an online thread entitled, AWB OneSky first light.

    Well there is about 500 of us in the OS thread that will agree with you.,This little scope can do a lot.,Mine gets much more airtime than any of my other choices..

    I just had mine out moonin with a new 17.5mm Morfeus eyepiece and the OS showed more craterettes than my AT102ED., go figger.,cheers

    clearwaterdave(Western Maine, USA), form an online thread entitled, AWB OneSky first light.

    Seeing was fantastic this evening right around sundown so decided to see what Venus had to offer in UV. Maybe my best details in Venus upper cloud features yet! I also captured a near infrared (685nm) version as well. Using the IR as red, UV as blue, and a mix of the two for green, it makes an interesting albeit false color representation of the planet.

    Attached Thumbnails

    • compilation_regi_175453_AS_P10_lapl6_ap28_conv.jpg

     

    jragsdale(Idaho, USA), from an online thread entitled; Venus in UV – 8″ Newt + ASI290MM

    Unless the seeing is abysmal, a larger telescope will always show finer detail than a smaller one with equivalent optical correction. My driveway typically has seeing that’s on the order of 3 arcseconds, and my 15-inch shows better planetary detail set up right next to the 10-inch. And the 10-inch similarly does better than my 4-inch refractor.

    The quoted seeing is typically FWHM (full width half maximum) of a profile of a star’s brightness based on images with long exposures, so it’s not good at telling an observer what the instantaneous seeing is. Veteran lunar/planetary/double star observers know to wait for moments of good seeing. The FWHM value may be 3 arcseconds, but during those brief intervals, it’s sub-arcsecond.

    Tom Polakis(Tempe, Arizona, USA), from an online thread entitled: Arc second seeing

    Hi, guys! I used an excellent 12.5-inch Cave Astrola Newt for about a decade and stared at stars directly and with knife-edge to scrutinize wavefront and Airy Disc. Thousands of hours of imagery and hundreds of hours staring at guide stars or KE patterns. I’d enjoy reasonable Airy Disc (tight core and one pretty stable ring) maybe 10% of the time. On great nights that would hold in, sometimes for up to a half-hour straight  And that is indeed in the neighborhood of the half-arc-sec you mention. Keep in mind, that is a very squishy benchmark, depending on the behavior of both your telescope and the atmosphere. The BIG scope 0.2 arc-sec transitions into the realm of ~wishful thinking~ even for the professionals. They are just as prone to exaggeration as we amateurs are… possibly more so.

    We were testing/scrutinizing a 12-inch imager for professional use, out in the lot aimed at a distant cell tower. Crummy atmospherics, sunny summer day, terrible thermals occasionally calmed by passing benign breezes. I put a beamsplitter in there and watched real-time video, so I could snap the shutter, whenever the image looked sharper than average. (Technique I had learned for improved stats on lunar and solar imagery). We collected hundreds of “select” images, and then went inside, to sift thru for the best ones. And, something rather amazing happened — anticipated, but still surprising. A few of the select images manifested half-arc-sec “perfect” resolution. I already knew that the lens wavefront was crummy, but the explanation goes something like this: If the system’s Zernike wavefront is badly-aberrated but smoothly-so (aka continuously differentiable) then at times (rare times) the atmosphere will improve (rather than degrade) the wavefront presented to the image. So, with sufficient (large) # of short-exposure snapshots, a few will be “diffraction-limited”. 

    Most of my assigned metrologies were spaced-based imagers. So, it is indeed true that an e.g. “Hubble-Class” big scope will and must resolve ~1/20 arc-sec to be considered ready to launch. Anything less is deficient. And that’s because the atmosphere is no longer the limiter.  

    Attached Thumbnails

    • 69 Tiny Airy Disc 150.jpg

     

    Tom Dey( Springwater, New York, USA), from an online thread entitled: Arc second seeing

    JimP, on 27 Feb 2020 – 11:28 PM, said:

    In terms of telescope resolution and planetary detail, I may have this wrong but it seems somewhere I read that the very best seeing conditions would be something around 0.4 arc seconds. Is this about right? If a 12” inch telescope has the ability to resolve approximately 0.4 arc seconds does this mean anything larger than 12” inches will show a brighter image but one is not likely to have seen conditions that will allow any finer detail to be seen. I know there are those of you out there who understand this far better than me so I await your thoughts.

    Jim

    Theoretical limits aside my 25″ blows away my 12 1/2″ scope any time any conditions. 

    Keith Rivich( Cypress, Texas, USA), from an online thread entitled: Arc second seeing

    While larger scopes can resolve smaller perturbations in the atmosphere, which means they virtually never see a “still” atmosphere, nonetheless, the seeing varies on a scale of days, hours, minutes, and even seconds.

    When the seeing is appreciably “sub arc-second”, the larger scope will reveal the details visible with that kind of resolution, while the smaller scope will see a more stable, yet lower-resolution, image.

    So in a given hour of the night, seeing will vary and the larger scope will occasionally reveal an image resolution not obtainable by the smaller scope.

    And, in the event of truly spectacularly-good seeing conditions (which happens occasionally where I observe), the larger scope will simply make the smaller scopes seem like regular resolution broadcast TV versus a 4K Blu-Ray disc image.

    You may not like the image in a big scope under mediocre seeing conditions, relative to the small refractor, but you will always see more if you look for longer than a few seconds.

    That assumes equal optical quality, though, a condition I think may be rare.

    Starman1( LA, California, USA), from an online thread entitled: Arc second seeing

    But the larger scope doesn’t have to operate at its theoretical limit to exceed the resolution of a smaller scope.

    It does have to have good optics, collimated and cooled, something I don’t see all that often.

    Starman1( LA, California, USA), from an online thread entitled: Arc second seeing

    JimP, on 27 Feb 2020 – 11:28 PM, said:

    If a 12” inch telescope has the ability to resolve approximately 0.4 arc seconds does this mean anything larger than 12” inches will show a brighter image but one is not likely to have seen conditions that will allow any finer detail to be seen.

    Jim

    The way I see it, as Tom Polakis said above, this is a measure of width of the seeing induced in-focus diffraction pattern over time. At times seeing will be as good or better and easily diffraction limited, at other times it will be less and fall below the diffraction limit. Both over shorter intervals. During the better moments, a slightly larger aperture should be diffraction limited for short intervals at least some of the time for a “diffraction limited” scope that is not otherwise compromised by poor collimation or thermal instability. When the scope and the seeing are both diffraction limited, the view can be amazing. The diffraction limit for seeing is about Pickering 7/10 or better, which should easily be the case for a 12″ resolving to the Dawes limit. I’d think the 12″ would be relatively steady and the larger aperture less so, but the larger aperture still performing to it’s limit at least some of the time. 

    This may likely be the case for a slightly larger aperture, adequately prepped and thermally stable for observing, so long as seeing effects at that larger aperture do not fall below the diffraction limit, i.e., in seeing less than about Pickering 7/10 all of the time. But, even then, a larger aperture is packing those induced seeing effects into a slightly smaller seeing induced diffraction artifact due to it’s increased resolution, so a larger aperture continues to retain most of it’s resolution advantage until, as Don says “you may not like the image in a big scope under mediocre seeing conditions”, which means and as Mitch describes, the aperture is bloating or speckling it’s star images. At that point, all bets are off. For stars at 0.4″ arc, anyway. 

    For extended object resolution, I agree with Jon in that the Dawes limit (0.4″ arc in this case) is not a good indicator of lunar or planetary resolving power. Dawes applies to two relatively bright high contrast point source diffraction patterns, not extended objects. When seeing is cooperating, we can actually see higher contrast detail to some degree well below Dawes. Even in the best seeing there are even better moments. During the best moments of the best seeing conditions, I’ve seen craters, in full crater form with a bright rim and a dark pit, on Plato’s floor that subtended an angular diameter of ~ 0.70″ arc less that Dawes calculated at 0.77″ arc for a 150mm aperture. I saw it three times during the time I was observing Plato’s floor at high magnification around 0.5mm exit pupil (300x in a 6″ aperture). That crater was less than a mile in diameter (near apogee IIRC). It has nothing to do with Dawes, only of (high) object contrast “transferred” to the image on very small scales. 

    Bottom line, as I understand it and somewhat by anecdotal evidence, in seeing that good there are better moments, coupled by the higher resolution of the larger aperture packing energy into smaller diffraction patterns, and that Dawes has nothing to do with extended object resolution. So, in my view, a larger aperture will still hold some or much of its resolving power until the tiny image begins to speckle and bloat in lesser seeing being affected by the aperture itself. I recall the general rule of thumb is, in theory and maybe empirically so, bloating will begin at about 3 times the aperture in diffraction limited seeing conditions. 

    Asbytec(Pampanga, PI), from an online thread entitled: Arc second seeing

     

    Here is a way of looking at the flaw in using Dawes or Rayleigh limits to discuss the amount of detail/contrast transfer in telescopes.

    Regarding the in focus diffraction pattern of a star.  There’s a central disc of light, then a dark ‘ring’ – the first minimum – and then the first bright ring, a second minimum, a second (much fainter) maximum and so on…..

    The radius, in arc seconds, to that first minimum is 138/D where D is aperture in millimetres..

    To the first ring the radius is 163/D,  (telescopoptics.net)  These numbers are a few percent smaller for increasingly obstructed scopes but for this discussion we will stay with unobstructed….Also let’s assume a fairly ordinary star of around 6th magnitude where the second bright ring is too dim to see…

    Imagine your 150mm scope is showing a beautiful, motionless first ring on a night of good seeing at 300x or so.

    The first minimum is at a radius of 138/150 = 0.92″  and the first ring is at a radius of  163/150 = 1.09″.   These numbers differ by only 0.17″, the dark space (depends on the brightness of the star) is, at most about 0.3″ across.  Yet you can clearly see it….if seeing allows. 

    This must mean that the  ‘balls of confusion’ are only about o.3″ or a bit less in size,  allowing you to see the diffraction pattern in all its glory in your 150mm scope.  At lower magnifications views will be ‘sharper’ and the views will be ‘tighter’ or more ‘refractor-like’ or whatever non-empirical descriptors you care to use…  Your 6-inch scope will perform to its resolution capability and deliver its very best contrast transfer in this scenario…  

    Now crunch these same numbers for a 16-inch scope.  400mm of aperture, so, first minimum will be at 0.35″ and the first ring will be at 0.41″ which differ by only about 0.06″ now and the black space between the disc and the ring will be barely 0.1″.

    On the same night assuming the same approx ‘balls of confusion’ of about 0.3″ the diffraction pattern,disc, dark space and ring will be smeared by the atmosphere into speckles or a fuzzball. No diffraction pattern for you!   The scope will not perform to its resolution capability nor achieve its best contrast transfer…

    BUT….

    The radius of this fuzzball in the 16-inch will be approximately 0.7″ (radius to first ring of 0.41″ plus about 0.3″ of ‘confusion’).  

    The bigger scope will still out-resolve and out-contrast-transfer more detail than the 6-incher!!  Even when you cannot see the diffraction pattern of stars in the 16-incher…

    Now all of the above are for a night of decent seeing where a 6-incher can clearly see its diffraction ring.

    Imagine much bigger ‘balls of confusion’ such that the 6-incher cannot see its diffraction pattern.  Just a fuzz ball maybe 1.0″ or 1.5″ in size.  ‘Balls of confusion of 1.0″ or even larger….. In this situation the 16-inch  won’t out-resolve or out-contrast the 6-inch.  The bigger scope will just show more detail/speckles in the fuzzball. 

    The latter scenario plagues most of us on most nights. 

    The TL;DR of all the above:

    On nights of mediocre/poor seeing where the diffraction pattern is completely smeared out in a 6-inch, the 16-inch will have little or no advantage in resolution or contrast transfer.  These nights are all too common.

    On nights of good/excellent seeing where the diffraction pattern is clearly seen in the 6-inch the 16-inch will still out-resolve and have better contrast transfer than the 6-inch even though the diffraction pattern is not visible.  These nights are less common but, at least in my neck of the woods, happen a dozen or so nights a year….

    On nights when the diffraction pattern is discernable in a 16-inch there will be glorious viewing for its owner and the 16 will truly ‘blow away’ the 6 in all categories of viewing..  These nights are exceedingly rare even in the florida Keys and are unknown where I usually observe…

    Cotts(Madoc, Ontario, Canada), from an online thread entitled: Arc second seeing

    ***

    Having tried a 6″ apo (the Explore Scientific), I can say that while they are nice, you will see more in a 10″ reflector for sure, unless there are significant optical defects or the cooling/collimationg are bad (both fixable, at least).

    If an 8″ reflector is optimized, it’s going to be hard to find a 6″ refractor that will beat it on the planets. For 10″, no competition.

    areyoukiddingme, from an online thread entitled, A Newtonian , SW150mm ED Refractor or SW180mm Mak?

     

    If an 8″ reflector is optimized, it’s going to be hard to find a 6″ refractor that will beat it on the planets. For 10″, no competition.

    True words.

    At a star party I attended, two friends had their scopes set up side by side. Seeing was decent and both scopes were pointed almost straight up at Jupiter. One scope was a 6″ f/15 Jaegers achromat and the view was very nice and crisp. I saw nothing to fault the view. Nice! The other scope was an 8″ f/6 Starfinder Dob. This scope had been “tuned up” with a high spec replacement secondary, minor tweaks and the original primary. Case closed – no need to run back and forth – the view was better in the Dob. Better brightness (expected), but more detail too. Beautiful!

    From my own perspective, I once owned an 8″ F/12 achromat and it gave nice planetary views. Side by side with my 10″ f/5, plate glass primary Dob – no contest – 10″ wins over the 8″.

    All the scopes in these comparisons had good optics – there weren’t any dogs in the race.

    You want to kill Mars? Better hurry up, it’s coming! Build yourself a 10″ Dob with great optics.

    Here is one (if still available) from our own CN classifieds. Royce 10″ f6 with Moonlight focuser diagonal rings

    Bargain for what’s included.

    siriusandthepup(Central Texas, USA), from an online thread entitled, A Newtonian , SW150mm ED Refractor or SW180mm Mak?

    A well built 10″ Newt with good optics simply cannot be beat.

    SteveG(Seattle WA, USA), from an online thread entitled, A Newtonian , SW150mm ED Refractor or SW180mm Mak?

     

    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,  published by Springer-Nature.

     

    De Fideli.

     

    A Fine Evening of Spring Double Star Observing with Octavius.

    Octavius; the author’s high performance 8″ f/6 Newtonian reflector on a night of excellent seeing.

    When the seeing is excellent and the weather is set fair, it pays to take full advantage of large aperture in the pursuit of tight double stars. Such conditions occurred on the evening of April 6 2020, so out came my favourite telescope; Octavius, a modified 8″ f/6 Newtonian reflector.

     

    Tune in soon to find out more………………

     

    De Fideli

    A Magical Evening with Plotina.

    Plotina; the author’s 130mm f/5 Newtonian still strutting her stuff.

    It’s hard to believe that four long years have gone by since I first discovered the considerable virtues of a modest 130mm f/5 flextube Newonian reflector. Like the larger 8-inch f/6 Newtonian I switched to in 2015, this 5.1 inch instrument has proven to be an excellent all-round performer, doubling up as a high performance spotting ‘scope by day and a fantastic grab ‘n’ go telescope at night, where its very decent aperture, fine optics, light-weight portabiity and quick cool down time has yielded excellent views of the Moon, bright planets, deep sky fuzzies and a whole raft of double stars.

    Shortly after testing the basic SkyWatcher unit, I invested in some modest-costing upgrades to further enhance the performance of this telescope. The secondary mirror was upgraded to one of higher quality and slightly smaller size (26.9 per cent linear obstruction). In addition, I had both the original SkyWatcher primary and upgraded secondary re-aluminised with Orion Optics UK’s proprietary HiLux coatings with 97 per cent reflectivity, giving an overall transmission of 90 per cent at the eyepiece once the area of the central obstruction is also factored in. The original flextube was replaced by a solid aluminium tube from a SkyWatcher 130P, providing a more stable arrangement for the secondary mirror housing. The tube was lined with cork and overlaid with flocking material to minimise stray light and increase image contrast. Finally, both the primary and secondary mirrors were equipped with Bob’s knobs to facilitate easy and quick collimation of the optical train. The resulting instrument sits pretty on a light weight alt-azimuth mount – a Vixen Porta II – which can be used both terrestrially and for astronomical observations.

    The Vixen erector lens system used to obtain correctly oriented views with Newtonian reflectors.

    In previous blogs I investigated ways to use this small reflector as a terrestrial spotting ‘scope, discovering methods to enjoy correctly oriented terrestrial views using a Vixen erecting adapter.The device allows the use of any eyepiece, thereby creating a spotting ‘scope with a much larger range of magnifications than those offered by conventional spotting ‘scopes. Its much greater light grasp allows me to enjoy crisp and bright high-power images well into twilight.

    The 130mm f/5 Newtonian in terrestrial spotting ‘scope mode using the Vixen erector lens.

    My 130mm f/5(aka ‘Plotina’) has travelled all over the British Isles with me, safely packed away in its foam-lined aluminium carry case, where it has sampled great skies in southern Ireland, northern England, Scotland and south Wales. These observations strengthened my conviction that there are many places where conditions are good enough to push the resolving power of this Newtonian telescope. Indeed, I have been able to split sub arc second pairs(0.9″) at ultra-high powers (up to 405x) in many of these locations. During summer heat, cool autumn and spring nights and freezing winter evenings, the telescope has never disappointed. Indeed, it has greatly exceeded all my expectations for it!

    Portable powerhouse.

    Best of all, it has saved me an absolute fortune, allowing me to completely break free from using small, expensive refractors, which became somewhat of an obsession with me for the best part of a decade. And quite frankly, to go back there again would be bonkers!

    February 25 2020 Observations

    Time: 21:20 to 23:15

    Conditions; Cold (1-2 C), mostly clear and transparent skies with no Moon and with intermittent blustery west or northwesterly gusts. Seeing very good (Ant II).

    Although the telescope optics takes a good 30 to 40 minutes to obtain the best high power images when taken from a warm indoor environment, it most certainly can be used with immediate effect if you start with low power wide field targets. I’ve recorded quite a few instances in which antagonists claim that the same telescope takes too long to acclimate to be a real grab ‘n’ go contender, but this is based largely on ignorance, laziness or just plain old lack of resourcefulness. In addition, it’s important to stress that I do not employ cooling fans on this or any of my other telescopes.

    Accordingly, I initiated the session with low power (26x), larger deep sky objects, beginning with some showpiece open clusters such as the Double Cluster in Perseus, which was beautifully rendered in the wide, 2.3 degree true field served up by my Celestron X-Cel LX 25mm ocular.  From there, I ventured over to the large and bright open cluster M34 (also Perseus) enjoying several dozen stellar members, many of which are arranged in neat double or triples(mostly telescopic in nature), and then ventured southward into Gemini now sinking into the western sky, where I enjoyed a stunning view of the expansive M35, the excellent light grasp of the reflector showing up many fainter members that are either invisible or very faintly rendered in smaller (4-inch and under) refractors. The 130mm F/5 is a particularly good telescope for observing this sprawling Messier open cluster, combining the near-ideal combination of aperture, magnification and field of view to fully immerse myself in the view.

    Camelopardalis was well situated high in the sky and so I sought out an opportunity to track down Kemble’s Cascade, so named after the late Canadian observer, and Franciscan friar, Father Lucian Kemble(1922-1999), who first called the amateur community’s attention to this remarkable, linear array of  15 or so stars tumbling down to the small open cluster NGC 1502 across the border in Cassiopeia. Spanning a full 2.5 angular degrees, Plotina was not quite able to encompass the cascade in its entirety. That said, the telescope served up a wonderful sight of stars ranging in brightness from the fifth to the 9th magnitude of glory. It is all the more remarkable that Kemble actually chanced upon this visually striking asterism using diminutive 7 x 35 wide-angle binoculars!

    After spending a few minutes drinking up the view of the mangnificent Beehive Cluster M44 in Cancer, the telescope was now sufficiently well cooled to crank up the power to get some close-up views of the three Messier open clusters in Auriga. For these, I employed a power of 118x(Meade Series 5000  5.5mm UWA) in a generous 0.7 degree true field. All three clusters are visually striking in the 130mm f/5 at this moderate power, but by far the most fetching in my opinion is M36, which transforms from a small foggy patch about one third of the size of the full Moon in 8 x 42 binoculars(also accompanying me at the telescope) into a granular mound of faint stars some 5 dozen strong. Increasing the magnification to 135x using my 4.8mm T1 Nagler improved the view still further by helping to pull the faintest members of this cluster out of the background sky.

    I was now ready to visit a suite of my favourite seasonal doubles well placed for observation on late February evenings. I began in Auriga, centring the bright white star Theta Aurigae. Cranking up the power 236x(Meade UWA 5.5mm and 2x Orion Shorty Barlow) and carefully focusing, I was delighted to obtain a near perfect image of the bright primary and the spark of the much fainter secondary tucked up close to it. This is quite a tricky system to image well though, and is thus a good test of seeing conditions at my backyard observing site, but tonight presented good conditions(as they often do here and elsewhere), so I knew that visiting a few other tricky systems would be a worthwhile pursuit on this fine evening.

    Off I sped to enjoy an easy system first; Castor A & B, which was beautifully rendered at 236x in the 130mm, the two bright components presenting as pure white Airy disks, with the much fainter C companion easily seen wide away. From there I moved the telescope a little way ‘down’ the western sky until I centred  creamy Wasat (Delta Geminorum). The challenge here is to bag the exceedingly faint and close-in companion shining nearly five stellar mangnitudes fainter. I have found, through experience, that the Meade UWA 5.5mm yielding 118x provides the most compelling view of this optically delicate companion. The older 4.8mm T1 Nagler is not as good as the newer Meade ocular in showing this system at its best. I attribute this to slightly better coatings applied to the newer eyepiece. Attempting to push my luck, I panned the telescope a little to the northwest to the lovely marmalde orange star, Eta Geminorum(Propus) but even after crankning up the power to 270x and 354x, I was unable to resolve its very close-in companion. That said, this system was by now well past meridian passage and sinking lower into more turbulent air in the western sky.

    As the evening progressed, Leo was now beginning to assert itself still somewhat east of the meridian. After a few minutes enjoying the rich aureal tints of Algieba(Gamma Leonis) and its companion, I panned the instrument southeastward until I centred Iota Leonis in the 6 x 30 finder accompanying the main telescope. This is quite a challenging system to resolve, consisting as it does of a 4th magnitude yellow-white primary and 7th magnitude secondary in a close-in orbit. Starting with 238x, I was able to discern the secondary as a tiny pimple like projection off the primary, but when I cranked up the power to 354x (3x Meade achromatic Barlow and 5.5mm Meade eyepiece),  and watching the system move rapidly across the field from east to west, I was finally able to see the secondary intermittently detached from the primary.  That said, I could have done with another hour and a half of waiting until it reached its maximum altitude in the south, but I was just happy to be able to resolve the system reasonably well at this earlier time of about 11pm local time.

    Re-visiting Cassiopeia, still well placed high in the northern sky, I was able to enjoy a wonderful view of the lovely triple system, Iota Cassiopeia, which was easily resolved into its three components at 236x with the 130mm Newtonian. Nearby Eta Cassiopeia, with its comely red and yellow components widely spaced at 236x was also a worthwhile system to visit on this cold February night. Images remained sharp, crisp and contrasty even at these high telescopic powers.

    Taking a quick break with my 8 x 42, I ventured to the front of the house, where I noted a rather lobsided Plough high in the northeast and lower down, the main stars of Bootes had by now cleared the murky air above the Fintry Hills to the east of the house. I then decided to move the telescope on its Vixen Porta II mount(which I can easily manoeuvre with one hand). Aiming my 6 x 30 finder at the two Alulas in Ursa Major, I centred each system in turn in the 130mm reflector. Alula Australis was truly a sight for sore eyes at 236x, the two stars presenting with beautiful, round yellow Airy disks separated by a sizeable sliver of dark sky. This is a fascinating system to watch with a small backyard telescope, where both 4th magnitude components complete one orbit of their barycentre in just 60 years! Ruddy Alula Borealis presented a different kind of challenge though, rather like Delta Geminorum observed earlier in the vigil. Using the very high contrast views of the Meade UWA 5.5mm, I was able to just make out the tiny and very faint spark of light of its close-in secondary at 118x.

    I ended this late February observation session by trying my hand at Epsilon Bootis(Izar), a favourite Spring binary system. still quite low in the east at or shortly after 11.15pm local time. Deciding on a moderately high power of 238x, Plotina managed a decent split of this gorgeous colour-contrast pair(yellow and blue), but its low altitude was, of course, attended by increased atmospheric turbulence.

    The title of this blog included the word, ‘magical,’ with the implication that there was something out-of-the ordinary about what the 130mm Newtonian can show. The truth is that these targets, especially the high-resolution systems discussed, can be enjoyed fairly routinely with this telescope from many locations(you just have to test them) and it is my fondest hope that others will take up the same challenges with their small Newtonian relectors.

     

    Neil English has created a considerable volume of literature highlighting the many attributes of the 130mm f/5 Newtonian. He is seriously considering writing a full length manuscript of his experiences with this transformative instrument at some time in the future.

     

    De Fideli.

     

     

    Chronicling the Golden Age of Astronomy: Still Going from Strength to Strength!

    The perfect Christmas gift for serious students of historical visual astronomy.

     

    Well, in the 18 months since it has hit the press, my new book, Chronicling the Golden Age of Astronomy has now received  20,000 downloads!

    A Big Thank You! to all of you who have supported my work over the years, despite some personal setbacks. 

    A New Review by Dr. Guillermo Gonzales( Professional Astronomer) and co-author of Privileged Planet with Jay Richards. Posted with the Permission of TouchStone Magazine.

    Stargazers’ Log

    Chronicling the Golden Age of Astronomy: A History of Visual Observing from Harriot to Moore
    by Neil English

    Springer, 2018
    (665 pages, $219.99, hardcover)

    Reviewed by Guillermo Gonzalez

    When I was asked to review Neil English’s new book on the history of visual telescopic observations, I jumped at the opportunity. Before I became a professional astronomer, I spent many nights (and some days) observing the heavens with my 8-inch f/7 Newtonian reflector in my homemade, backyard, roll-off-roof observatory in the suburbs of Miami, Florida. When I look through the eyepiece of a telescope to observe a planet, the moon, or a deep-space object, I feel I am making an intimate connection with the great observers of years past. And I can share in their joy in reading God’s great book not written with words and freely accessible to all with normal vision.

    Unfortunately, Chronicling is far from free. Only a relatively few individuals with a strong interest in science history and telescopic observation will want to hand over $200+ for a copy. I would think that school libraries with a substantial science section are the most likely purchasers.

    English is eminently qualified to write this book, having been a regular contributor to the British amateur astronomy magazine Astronomy Now for 25 years. Evidence of this can be glimpsed in some of the book’s 41 chapters, wherein he employs his extensive background knowledge to bring helpful insights to bear on historical questions. For example, in 1611, at a meeting with members of the Collegium Romanum, Galileo had the members look through his telescope. Some claimed they could see nothing through the telescope. English notes that this is likely because Galileo’s telescope had a very narrow field of view and required placing the eye just right to see through it (20).

    The chapters in Chronicling are arranged roughly chronologically, but each is self-contained. Each is about an astronomer, a telescope, an important published work, or an astronomical phenomenon. Though together they are an eclectic mix, the emphasis in each chapter is almost always on history, often in the form of a biography. The main exception is the chapter on Walter Scott Houston’s “Deep Sky Wonders.” English also interweaves astrophysical concepts throughout, and he even throws in a few equations. At times, a chapter might resemble a college-level introductory textbook on astronomy.

    Still, the book is an easy read and includes many illustrations. English has a gift for presenting history in an engaging way. He makes all sorts of connections between the subject of a given chapter and that person’s contemporaries.

    Men of Faith

    Why would a reader of Touchstone be interested in this book? I can give several reasons, some of which are obvious. For instance, there’s the “Galileo Affair.” English writes that “the mythologized view of Galileo standing for truth and reason versus religion and superstition of the Roman Catholic Church is not at all accurate” (20). Historians of science know what science popularizers don’t, and English has clearly read the former’s books (which he lists at the end of the chapter). His lengthy chapter on Galileo is an excellent summary of modern scholarship.

    Those interested in topics related to science and faith will not be disappointed. From the very first chapter, English does not shy away from discussing the religious beliefs of the telescopists. For instance, Thomas Harriot actually turned his telescope towards the heavens before Galileo did. But how many atheist–narrated TV documentaries on astronomy would also mention that Harriot translated the Lord’s Prayer into the Algonquin language? (8).

    In fact, most of the telescopists of the Golden Age of Astronomy were Christians. A number were Jesuit priests, such as Christoph Scheiner (Chapter 1) and Angelo Secchi, the “father of modern astrophysics” (Chapter 22). Several were “clerical astronomers”: William Dawes (Chapter 14), Thomas Webb (Chapter 15), and Theodore Philips (Chapter 30). Of Webb, English writes,

    Despite the growing power of scientific naturalism with the later Victorian society, Webb couched everything, with firmness and gentleness, in terms of the Biblical God he believed in. Seen in this light, his astronomical writings, and his devotion to exploring the wonders of Creation with his telescopes, were more like prayers than anything else.

    As if it even has to be said (and sadly it does), the evidence is clear that having a strong Christian faith does not hinder a person from being a successful scientist. On the contrary, the great works of many of the telescopists English describes are testimonies to the motivating influence of their faith.

    To the believer, this should not come as a surprise. More than other aspects of the Creation, the starry heavens seem to evoke from us a sense of the divine. The Psalmist wrote,

    The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they display knowledge. There is no speech or language where their voice is not heard. Their voice goes out into all the earth, their words to the ends of the world. (Psalm 19:1–4)

    Kepler voiced eloquently what other great astronomers must have believed, that he saw himself as a kind of “priest of God” at the pulpit, reading the “book of nature” as an act of worship, to “think God’s thoughts after Him.”

    A Rare Sneak Past the Censors

    What did catch me off guard were some of English’s comments on Darwinism. For instance, when commenting on Percival Lowell’s ideas about life on Mars, English writes, “To begin with, scientists were gloriously unaware just how complex even the simplest forms of cellular life were during the late nineteenth and early twentieth centuries. . . . Lowell, like Darwin, thought the cell to be merely composed of blobs of protoplasm” (386). Later, English comments thus on Lowell’s beliefs about life beyond Earth: “Many scientists anticipate that life will be commonplace in the galaxy, but this is based on Darwinian reasoning. However, there are many scientists who now doubt the Darwinian paradigm and do not expect life to be commonplace, as has been widely believed in the past” (397). English is qualified to comment on Darwinism, as he has a Ph.D. in biochemistry.

    I agree with English’s stance on Darwinism, but what surprised me was finding his comment in a book published by Springer. The editor must have been asleep at the keyboard! It also is interesting that English lists Hugh Ross’s book, Improbable Planet: How Earth Became Humanity’s Home (Baker, 2016), in the sources to the Percival Lowell chapter. He lists another of Ross’s books in the sources to the chapter on Clyde Tombaugh (Chapter 32). We are in a sad state when the censorship of certain scientific ideas in the public square has become so common that we feel we must jump up and cheer when someone boldly sneaks a few “forbidden” thoughts past the censors.

    I would recommend this book to anyone interested in amateur and professional telescopic astronomy, the history of science, and the relations between science and faith. 

     

    British Astronomical Association(BAA) Review by Archivist, John Chuter

     

    Cloudy Nights Review

     

    Stargazer’s Lounge Review

     

    Endorsements:

    “This is an excellent book and will complement Ashbrook’s Astronomical Scrapbook and therefore have wide appeal to both amateur and professional astronomers.”
    Wayne Orchiston, Professor of Astrophysics, University of Southern Queensland.

     

    New Citation here

     

    To Be Continued……………………….

     

    De Fideli.

    A Magical Hour with my 130mm F/5 Newtonian.

    A grab ‘n’ go telescope on steroids.

    Anno Domini MMXIX

    My conversion to Newtonian telescopes continues apace. Though I’ve had my wonderful 130mm f/5 Newtonian travel ‘scope for a few years now, it never ceases to impress me. And my observations on the freezing night of November 18 with the same instrument only served to consolidate those sentiments.

    I set the telescope out on its trusty Vixen Porta II alt-azimuth mount about 10.30pm local time and tweaked its collimation before leaving it to cool down from an indoor temperature of 20C to an outside temperature of -5C. The optical tube is quite rigid and it holds accurate collimation very well, which is fine for general observing, but I always fine-tune the alignment of its two mirrors when going after the tightest double stars. I knew conditions would be good for such an activity by noting how little Vega was twinkling low down in the western sky, while bright stars like Capella and Mirfak located high overhead shone with a steady, planet-like gleam.

    The tube is insulated with a thin layer of cork and overlaid by black flocking material. I have noted that this affords extra thermal stability to the telescope, especially as temperatures drop rapidly(as occurs during acclimation on these cold nights). I do not use any air-blowing fans to accelerate cooling of the primary mirror, but this has never really been an issue with this small Newtonian telescope.

    After enjoying a lengthy binocular session using my 20 x 60 on a simple monopod, I began an hour of telescopic observations on a number of seasonal double stars, beginning about 11:20pm. Orion was quite well placed  east of the merdian, so I inserted my Meade 5.5mm UWA yielding 118x on a fairly low lying Rigel, carefully focused and observed the stellar image. Wow! What an amazing apparition! I was greeted by an intensely bright image of this white supergiant star, with beautiful diffraction spikes radiating outwards from a calm Airy disk. And just a little to its southwest, its faint close-in companion was easily discerned. That was enough of a confirmation that seeing conditions were indeed very good, so from there I panned the telescope northward to the better placed belt stars of Orion, examining both Mintaka and Alnitak at the same power. The images of both stellar systems were lovely and calm, with beautiful hard Airy disks betraying their companions with ease.

    From there, I moved up to a more challenging system, 32 Orionis, located just a few degrees east-southeast of Bellatrix. Coupling a 3x achromatic Barlow lens to the Meade 5.5mm yielding a power of 354x, I carefully focused the image, watching it as it raced across the field of view. Sure enough, its close-in companion(separation ~ 1.3″) proved easy pickings for this light-weight 5.1-inch telescope situated just off to the northeast of the primary. Before leaving the celestial Hunter, I had a quick look at Eta Orionis, another fine, high-resolution target, consisting of a magnitude +3.6 primary and a tight, magnitude +4.9 secondary. Both were nicely resolved at 354x, and roughly orientated east-to-west.

    Pointing the telescope at majestic Auriga, now very high in the sky, I trained the instrument at Theta, an old friend, and backed the magnification down to 236x by swopping out my 3x Barlow for a 2x Orion Shorty. That was more than enough to resolve its ghostly companion in the still midnight air.

    I spent the next quarter hour exploring some favourite doubles in Cassiopeia, notably the lovely colour contrast pair, Eta Cassiopeiae, admiring the textbook perfect images of its yellow primary and ruddy secondary at 118x. And from there I moved to Iota Cassiopeiae, beholding this beautiful triple system at 236x. These views inspired me to swing the instrument westward into Andromeda, where I quickly tracked down another binary superstar, Almach, where the telescope showed me a gorgeous, crisp image of the orange primary and widely separated blue secondary at 118x.

    After a quick look at Castor A, B and C at 118x, I trained my eyes on Propus, the ‘orange nemesis,’ as I have come to call it, which by now was reasonably well placed but still a few hours from culminating in the south. This system requires very high powers, so I broke out my 4.8mm T1 Nagler and coupled it to my 3x Barlow lens, delivering a magnification of 405 diameters. Carefully focussing the star, I watched it cross the field of view several times, observing its behaviour at this ultra-high power. During some moments, the system swelled up to become a rather unsightly seeing disk owing to a combination of thermal stress and variations in seeing, but sure enough, there was always prolonged moments where the image came together, as it were, allowing me to carefully examine the stable Airy disk. And it wasn’t long before I began to see the little blue pimple of light from its tiny secondary touching the marmalde orange primary. Having examined this system quite a few times with the 130mm Newtonian over the last few years, I have learned that good seeing doesn’t always yield commensurately good results. This I attribute to the slightly variable nature of this post-main sequence star, which can often hide the companion. But tonight, my patience paid off!

    Plotina: strutting her stuff at -5C.

    I ended the vigil shortly before half past midnight local time, by moving the telescope from my back garden to the front of the house, where I was greeted by the light of a silvery last quarter Moon, hanging above the Fintry Hills to the east. Inserting the little 4.8mm Nagler delivering 135x, I enjoyed some wonderful, crisp images of the battered lunar regolith, particularly the majestic Apennine Mountains strewn across its mid-section, near the terminator, as well as the magnificent desolation of the heavily cratered southern lunar highlands.

    Simple pleasures of a telescope.

    It was good to get out. But it was equally nice to retire the telescope indoors and reflect on the experience, sat next to a warm coal fire.

     

     

    De Fideli.

     

     

     

    On the Campaign Trail: Again!

    Image result for Roman battle Gladiator images

    I decided to go on campaign again over the weekend of October 26/27 2019. This time it was in response to a provocatively titled post by a guy I helped secure a book contract for some time ago. The thread in question was entitled,  Evolution tells us we might be the only intelligent life in the universe.

    While I agreed with the conclusion, I took issue with the mechanism, or rather the lack of a mechanism implied by the poster; Darwinian evolution. I responded by posting a number of links to the conclusions drawn from an expert in the fossil record, Dr. Gunter Bechly, who defected from neo-Darwinism to join the intelligent design movement, based on the enormous body of new evidence that shows no intelligible Darwinian progression. Despite this data being freely available for over a year now, the poster seemed to reveal a complete ignorance of the true status of this failed ideology masquerading as science.

    I reinforced Bechly’s talk with a number of other short, supplementary links, explaining in simple terms, how neo-Darwinism has now been disproven and is no longer tenable as an explanation for the origin of biological systems:

    How has Neodarwinism been disproven?

    What is the waiting time dilemma and how does it refute Neodarwinian evolution?

    How does the evolution of whales present a challenge to Neodarwinism?

    Most of the earlier posters digressed into discussions more along these lines than anything else; wishy-washy New Age dribble.

    As expected, the exchanges garnered a substantial number of viewers, growing from about 800 to ~1600 hits in the space of 24 hours. Like I explained in earlier campaigns, folk have a bizarre attraction to conflict. They just can’t help themselves it seems! I got the usual emotive and hostile response from predatory trolls, who hurled abuse at me, but never discussed the factual content of those links. One person responded positively in my defence, but stated that he was neither religious(nor am I for that matter, as Christianity is not a religion but a relationship) nor an endorser of intelligent design. That’s all well and good, but he couldn’t proffer an alternative naturalistic explanation. My question to that person is: if it’s not Darwinian evolution, how does one best explain the 18+ big bangs that have occurred throughout the long history of life?
    I believe that the answer is that new information from an outside source was required to bring about those changes in the fossil record. And that information provider was the God of the Bible.
    The same chap who came to my defence asked why I believe humanity is alone in the cosmos? Why wouldn’t an intelligent designer like the Lord God Almighty not create other civilizations? Some of my reasoning comes from the general observation that every where(apart from Earth) we look in the cosmos, conditions appear to be hostile toward life. I provided those scientific details in my debut feature article for Salvo Magazine Volume 50(fall 2019 issue). Although I was not at liberty to discuss the theological reasoning behind my conclusions on such a forum, I think one reason is grounded in a kind of pagan idolatory. I see these mythical advanced civilizations as a distraction from our true duty to look out for and help one another and to responsibly steward all other life on this jewel planet we live on. Like I said before, the only aliens we are ever going to meet are our neighbours!  This talk by Dr. John Barnett fleshes out still more theological reasons why I do not believe in the existence of ETI.
    In summary, I view this latest online campaign against general scientific ignorance as a success. It is my fondest hope that some people who read that thread will come to a knowledge of the truth.
    Sincerely,
    Neil English PhD.
    Postscriptum: Once again, I got physically sick(I threw up) after the thread linked to above was locked.The same thing happened in the aftermath of my last campaign.

     

     

    What I’m Reading.

    “Escaping the Beginning? Confronting Challenges to the Universe’s Origin.

    Did the universe have a beginning—or has it existed forever?

    If the universe began to exist, then the implications are profound. Perhaps that’s why some insist it has existed forever.

    In Escaping the Beginning?, astrophysicist and Christian apologist Jeff Zweerink thoughtfully examines the most prevalent eternal-universe theories—quantum gravity, the steady state model, the oscillating universe, and the increasingly popular multiverse. Using a clear and concise approach informed by the latest discoveries, Zweerink investigates the scientific viability of each theory, addresses common questions about them, and then focuses on perhaps the most pressing question for believers and skeptics alike: If the evidence continues to affirm the beginning, what does that imply about the existence of a Beginner?

    About the Author: Jeff Zweerink (PhD, Iowa State University) is an astrophysicist specializing in gamma-ray astrophysics. He serves as a senior research scholar at Reasons to Believe and as a part-time project scientist at UCLA. He has coauthored more than 30 papers in peer-reviewed journals and numerous conference proceedings.

     

    Some Reviews Thus Far Garnered:

    “In Escaping the Beginning? Jeff Zweerink leads the reader through a fascinating tour of the scientific development of the big bang theory as well as the theological and philosophical implications of the beginning of our universe. More importantly, he addresses some of the recent speculations by scientists that attempt to circumvent both a beginning and a Beginner and shows that the best current scientific evidence continues to point to an actual beginning of our universe. The hypothesis that the universe came into existence through the actions of a transcendent intelligent Creator is still arguably the explanation that best fits the scientific data.”

    —Michael G. Strauss, PhD
    David Ross Boyd Professor of Physics
    University of Oklahoma

     

    “As an atheist detective investigating the existence of God, I hoped the evidence would reveal an eternal universe without a beginning because I knew the alternative would be hard to explain from my atheistic worldview. . . . Escaping the Beginning? examines the evidence for the universe’s beginning and the many ways scientists have tried to understand and explain the data. I wish I had his important book when I first examined the evidence. If I had, I would probably have become a believer much sooner.”

    —J. Warner Wallace
    Dateline-featured Cold-Case Detective
    Author of God’s Crime Scene

    “There are few books I read twice. but this is one of them. Although understanding this book will take effort  for anyone untrained in the sceinces, the effort is well worth it. Dr. Zweerink answered many of my questions about the existence of the multiverse, evidence for the beginning of the universe, and problems for common challenges to divine creation. . . . Escaping the Beginning? deserves wide readership by believers and skeptics alike.”

    –Sean McDowell, PhD, Author of Evidence that Demands a Verdict

     

    “Jeff Zweerink has done something I might have thought to be impossible. He has made cosmology accessible to scientific laypersons like me. Whether it’s quantum fluctuations, inflation theory, or the various models of the multiverse, Zweerink explains things clearly and with good humor. Even more importantly, he shows that the findings of modern cosmology give Christians even more reason to worship and adore our great God who created all things.”

    -Kenneth Keathley

    Senior Professor of Theology, Southern Baptist Theological Seminary.

    “Does the universe have a beginning, or has the physical realm existed forever? This is an ancient question and still hotly debated today. The interest in the subject is not just from its obvious scientific significance, but also from its religious implications. Since the first cosmological and theoretical evidence for a universe with a distinct beginning was discovered a century ago, some of the most intense opposition among scientists to the notion of a beginning has been primarily on religious grounds. In this engaging book, Jeff Zweerink reviews the state of the theory and experiment, and argues that far from having been escaped, a bginning to the universe is the likely outcome of the current lines of research.”

    -Bijan Nemati

    Principal Research Scientist, University of Alabama in Huntsville.

    “Did the universe have a beginning? If so, what would that imply? Does the origin require an Originator? Does a creation imply a Creator? What would that mean for our lives?

    Paul Valery once said, “What is simple is wrong, and what is complex cannot be understood.” Dr. Zweerink splits the horns of this dilemma by raising many of the issues surrounding a cosmological beginning in an enjoyable  and accessible format for a general audience. yet this is done without sacrificing the critical details that attend the state-of-the-art.

    He draws on his training and expereince as an astrophysicist to unpack the history of the big bang, its blossoming into the universe around us, and otther topics of fascination, interest, and wonder. Dr. Zweerink then goes to the heart of contemporary cosmology to find out what today’s cosmologists – our secular priests -are saying about cosmic origins.

    While I might believe the scientific case for a beginning and a Creator is a bit stronger than Jeff does, his grasp of the issues and presentation style will serve his audience well.”

    -James Sinclair

    Senior Physicist, United States Navy.

     

    “I had the privilege of debating Jeff Zweerink on two occasions. As an atheist, I was surprised to see how much common ground there was between us. And that is because Jeff is an incredibly honest and thoughtful person and his writing reflects that. Escaping the Beginning? is a well-written and carefully researched work that doesn’t shy away from challenges to cherished belief and deserves to be widely read by the community. It does what a good book should do—educate and (I hope) stimulate thoughtful debate.”

    —Skydivephil
    Popular YouTuber and Producer of the Before the Big Bang Series
    Featuring Exclusive Interviews with Stephen Hawking, Sir Roger Penrose,
    Alan Guth, and Other Leading Cosmologists

     

    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.