Spectrum

Take a Closer Look.

 

In this blog, I’ll be exploring subjects of general interest/concern to me and wider society in this age of mass deception and rapid moral decline:

 

The Dark Side of Transgender Medicine

 

How the Media Manipulates Truth

 

Cogito ergo sum

 

The Secular Case Against Homosexuality

 

Our Fragile Home

 

The Anti-Social Network

 

A Form of Child Abuse

 

Cool stuff you never hear in Church

 

The Rise of Homeschooling

 

James Clerk Maxwell: a Great Life Lived

 

Reasonable Faith: An Interview with Professor Alvin Plantinga

 

Doubting Dodgy Science

 

Evaluating World Views

 

Depraved Minds

 

The Beauty of the Creation

 

The Preciousness of Free Speech

 

Walking your Way to Good Health

 

Did the Eye Really Evolve?

 

Unholy Alliance: when Dodgy Science Merges with Theology

 

The Truth about UFOs

 

The Rise of Neo-Paganism

 

From Spiritual Shipwreck to Salvation

 

The Rise in Euthanasia Killings

 

The Greatest Story Ever Told

 

Holocaust Survivor

 

Coming Soon to a Town Near You: The Rise of Bestiality

 

The Death of Naturalism

 

Anything Goes

 

From Gaypo to Paedo

 

When Scientists Lose the Plot

 

The Sixth Mass Extinction Event in Our Midst

 

‘Depth Charging’ the Values of the Ancient World

 

The Truth about the Fossil Record

 

AI

 

The Language Instinct

 

Not the Same God

 

Greening the Deserts

 

Moving the Herds

 

Evolutionary Atheist gets his Facts Wrong…..Again

 

Distinguished MIT Nuclear Physicist Refutes Scientism

 

Pursuing Truth

 

The Dangers of Yoga

 

Pseudoastronomy

 

Get thee right up thyself! : The New Transhumanist Religion

 

The Biblical Origin of Human Rights and why it’s a Problem for Atheists

 

A Closer Look at the Israeli-Palestinian Conflict

 

Winds of Change: Prestigious Science Journal Concedes Design

 

A Distinguished Chemist Speaks the Truth

 

The Scourge of Pornography

 

Eye

 

Bart Ehrman Debunked

 

An Evil Generation Seeks After a Sign

 

Magnetic Pole Shift

 

Decimation of Global Insect Populations

 

The Spiritual Suicide of a Once Christian Nation

 

Mass Animal Deaths Worldwide

 

Not Going Anywhere

 

UN Report: World’s Food Supply under ‘Severe Threat’ from Loss of Biodiversity

 

False gods of the New Age

 

From Abortion to Infanticide in the “Land of the Free”

 

Sports Personalities Speak Out Over Transgender Athletes

 

Magonus Sucatus Patricius

 

Celebrating a Killing

 

Human “Out of Africa” Theory Debunked

 

The Other Side of the Rainbow

 

Vintage James Tour: How to Cook Up a Proto-Turkey

 

Big Brother Watching

 

Follow the Evidence: The Problem of Orphan Genes

 

Follow the Evidence: The Genius of Birds

 

The Butterfly Enigma

 

Man’s Best Friend

 

Darwinian Evolution On Trial Among Biologists

 

New Fossil Finds Thwart Human Evolutionary Predictions

 

Global Persecution of Christians

 

 Ratio Christi

 

Questions About the Qur’an

 

Engaging with Islam

 

Calling Evil Good

 

Parousia

 

Tall Tales From Yale: Giving up Darwin.

 

More on the Proto-Turkey:  Dr. Tour Responds to Cheap Shots from the Pond Scum Merchants

 

Good Riddance: Despicable British TV Show Axed after Death of Participant

 

There’s Heehaw Out There…ken.

 

The Fastest Growing Insanity the World has Ever Seen

 

Pharmakeia

 

Darwinism & Racism: Natural Bed Fellows

 

The Modern Root of Anti-Semitism

 

Jesus & Archaeology

 

A Victory for Common Sense: Transgender Weightlifter Stripped of his Medals

 

The US Equality Act: A Plea for Caution

 

Reunited: Music & the Human Spirit

 

Gladys Wilson

 

1st Century Christian Insight: The Didache

 

The Clothes Maketh the Man

 

Why Some Books were Left Out of the Bible

 

Why the Human Mind is not Material

 

What God Thinks of Scientific Atheism

 

For the Love of the Creator

 

An Essential Component of a Modern Education

 

Peace Cross

 

Earth: “Presidential Suite” of the Universe

 

How to Really Stand Out in a Crowd

 

Straight from a NASA Scientist: Jewel Planet

 

The Singularity

 

No Life Without Super Intelligence

 

Darwinism as a Cargo Cult

 

Body Plan Development Raises New Headaches for Evolutionists

 

Membrane Biochemistry Stymies Evolutionary Origin of Complex Cells

 

Science Speaks: Common Abortafacients Harmful to Both Mother & Child

 

Biblical Ignoramus Twists the Words of Christ

 

The Multiverse: Just Another Religion

 

Apologia Part I

Part II

Part III

Part IV

Part V

Part VI

 

Attention Parents: American Psycho Association Promoting Polyamory to Pre-Teens as ‘Ethical.’

 

The Only Rainbow God Recognises

 

Calling Time Out on Evolutionists’ Failure to Explain The Cambrian Explosion

 

7 Reasons to Reject Replacement Theology

 

Psychiatric Diagnoses are ‘Scientifically Meaningless’ Study Shows

 

Out of a Far Country: A Gay Son’s Journey to God

 

Universalism Debunked

 

The Prosperity Gospel Debunked

 

New Science Reveals First Cellular Life to be “Amazingly Complex”

 

New Law Firms Being Established to Counter the Rise in Christian Persecution

 

Playing the Numbers 32:23 Game

 

Multiple Lines of Scientific Evidence Converge on 3rd Century BC Age of the Famous Isaiah 53 Scroll.

 

Meet the Gestapo

 

Exposed: Theologians Deceived by Darwinian Ideology

 

New Insights into the Shroud of Turin

 

What we Know and Do Not Know About the Human Genome

 

Debunking Da Vinci Code Tosh

 

Sorry: No Such Thing as “Gay” Penguins

 

Genetic Entropy

 

Dunderheid Alexa

 

The Extinction of Reason

 

A Biblical Perspective on Diet

 

Revelation: Number of Transgender People Seeking Sex Reversals Skyrockets

 

Psychologist Debunks Pseudoscientific Explanations for Human Love & Compassion

 

The Dismantling of the Feminine

 

Disturbing Trends in the Roman Catholic Church

 

N = 402

 

The Nazareth Inscription

 

A Christian Response to Halloween

 

Seeking Methuselah

 

Beware the Enneagram

 

No Safe Spaces!

 

Pale Blue Dot

 

Encyclopedia Galactica

 

Phillip E. Johnson: A Tribute

 

The Darwinian Response to Human Life: Let the Baby Die!

 

The Best Explanation for Beauty

 

What is Feminism?

 

Insects & Light Pollution

 

Candy-Ass Christianity

 

Antiobiotic Resistance in a Post-Darwinian World

 

Adam & Eve: Redux

 

Joyce Meyer

 

Michael Behe Says No to Theistic Evolution

 

New Atheism: An Autopsy

 

Serenading an Old Girl.

 

“Progressive” Christianity as a Political Cult.

 

Israel Folau Vindicated

 

The Church of Satan, Sweden

 

A Rational, Christian Response to Humanism

 

More Depravity: the Sexualisation of Children

 

Shameful Humanity:  Murder of the Unborn Now the Biggest Worldwide Killer.

 

Origin Stories

 

Privileged Planet

 

Brokeness

 

Sorry Sam Smith, You’re Still a ‘He.’

 

Nature Genetics: How ‘Evolutionary Thinking’ led Biologists Astray about Pseudogenes.

 

A Kindgom Divided Against Itself: Why Evolutionary Psychology is Bunk

 

Of Melting Glaciers and Darwinism

 

First US President Addresses 47th March For Life, as theSecular Media Duck for Cover

 

Wolves Among the Sheepfolds

 

The New Science of Separate, Distinct Creations

 

That Sacred Space

 

Faith of the Fatherless

 

More Tales of Darwinian Thuggery

 

Keeping your Children Strong in the Faith

 

Former Editor of Nature Waves Bye Bye to the RNA World

 

At Scientific American: Physicist Pours Cold Water on Scientism

 

A Biblical Perspective on Alcohol Consumption

 

High Priest of a Pseudoscience Rears His Ugly Head Again

 

Another Step into the Human Immorality Sewer: Normalizing Throuples & Sologamy

 

Symptom of a Depraved Society: Scientists Now Fighting to Affirm a Basic Fact of Life: Sex is Binary

 

Speaking the Truth in Love: Where the LGBTQ Community is Ultimately Headed

 

The Power of Biblical Prophecy: The Triumphal Entry of Jesus into Jerusalem

 

Origin of Life Debate: James Tour versus Lee Cronin.

 

7 Rock Solid Scientific Arguments for the God of the Bible

 

SETI@Home Shuts Down

 

An Existential Crisis in Neuroscience

 

AI Hype and the End of Moore’s Law

 

Discerning Fact from Spin/Fiction in Cosmos 3.0

 

Polly’s No Statistician!

 

Why All the King’s Horses and All the King’s Men Cannot Put Humpty Together.

 

COVID-19

 

The James 5:16 Phenomenon; the Healing Power of Prayer

 

Heart of Darkness: Organ Harvesting of Chinese Prisoners

 

Confessions of a (yet another) Darwinian Sceptic

 

Selflessness

 

Darwinism as a Mentally Retarding Virus

 

Who is the God of the Bible?

 

Legendary Biologist Claims Atheism has Nothing to do with Science

 

Why Nature Should Never be Worshipped

 

What ‘Evolutionary Theory’ is Really Good at Explaining: Cancer.

 

Avoiding the Most Deadly Virus of All

 

The Prince of Peace Versus the Prophet of Islam

 

Coronavirus Outbreak Spurs Record Bible Sales

 

More Tales of Woe for Darwinian Junk Science: No Such Thing as Pseudogenes

 

Earth Fine-Tuned for Space Exploration

 

Pious Frauds

 

The CCP Virus

 

By the Rivers of Babylon

 

Progress: US College Board Drops Natural Selection from its AP Biology Exam

 

Abiogenesis & the Tooth Fairy

 

A Whale of an Evolution Tale

 

New UN Report: COVID-19 will Produce Famines of ‘Biblical Proportions’

 

American Schism

 

An Interview with Dr. Frank Turek

 

The S-Blob

 

Post Pandemic Prospects

 

Neanderthal DNA & the Leviticus 18:23 Question

 

Debunking Scientific Materialism through Mathematics

 

Incompetent Experts & Bad Government

 

Intelligent Design Now Thriving in Europe

 

Cosmic Fine-Tuning: an Interview with Christian Cosmologist, Dr. Luke Barnes.

 

God TV Given the Green Light to Broadcast on Mainstream Jewish Cable Networks

 

Ivy League Philosopher Dismisses Evolutionary Psychology as  Pseudoscience

 

Preterism Debunked

 

Ravi Zacharias(1946-2020) RIP

 

Sol Watchin’

 

Ten Things you Need to Know about Scientism

 

Why Humans have Souls

 

Freeman Dyson: God is a Mathematician

 

J.K. Rowling Takes a Stand Against Militant LGBT Activists

 

Humans Together

 

Talking about Racism

 

Lest we Forget: William Wilberforce

 

Update on the Long Term Evolution Experiment(LTEE): Sickening News for Evolutionists

 

An Interview with Mathematician William Dembski

 

Fatherless America

 

A Technical Look at Fine-Tuning in Biological Systems

 

David Pawson(1930-2020) Remembered

 

The Colour of Christian Art

 

Date Setters

 

Punctuated Equilibrium Debunked by Researchers

 

Harari’s Fictions

 

For the Attention of Greta Thunberg

 

Rebels Without A Clue

 

Why We Should Cancel Darwin

 

No Ordinary Star

Product Review: Viking Optical Kestrel 8 x 42 Binocular.

The Viking Optical Kestrel 8 x 42 binocular.

A work begun July 1 2020

Preamble:

Review 1

Review 2

Review 3

Review 4

Specification: 8 x 42

Eye Relief: 17.2mm

Field of View: 8.1 angular degrees (142m@1000m)

ED glass: Yes

Body: High density Polycarbonate, textured rubberised overcoat.

Weight: 692g

Coatings: Fully Multi-Coated

Dielectric Phase Coating: Yes

Dimensions: 12cm x 12cm x 4.5cm

Nitrogen Purged: Yes

Waterproof: Yes (1.5m for 3 min)

Tripod Mountable: Yes

Accessories: Padded soft case, high quality lanyard, instruction sheet

Warranty: 10 years

Retail Price: £205 UK

 

The British optics firm, Charles Frank of Glasgow, has been selling and repairing optical instruments for nearly three and a half decades. In 2016, the firm moved south to Halesworth, Suffolk, where they changed their name to Viking Optical. Recently, the company launched an exciting range of affordable roof prism binoculars featuring a number of impressive optical features exhibited in their Kestrel, Merlin and Peregrine(all keen eyed raptors) binoculars. Three models are offered in 8 x 32, 8 x 42 and 10 x 42 configurations, and all feature fully multi-coated optics, dielectrically coated and phase corrected BAK 4 prisms and objectives containing ED glass elements in a fully waterproof housing. Although all these models are assembled in China, I reasoned that their acquired knowledge in repairing binoculars over many years would put them in a strong position to offer a quality experience, so I pulled the plug and decided to order up the 8 x 42 Kestrel model for optical testing and evaluation.

First Impressions

The package as received.

The binocular was ordered up from Amazon and the instrument arrived in the evening of the following day. I was immediately impressed with the packaging of the Kestrel. Instead of the regular colour-saturated cardboard box that usually attends many of the binoculars that have passed through these parts, I received a very fetching presentation box with the phrase “Extend Your Horizons” printed on top. After removing an outer slip case, the binocular and accessories were carefully packaged away inside.

The inner box containing the binocular and accessories features an inspiring outdoor scene.

The package contained the binocular inside its soft padded case, a high quality padded neck strap and one page instruction sheet with details of the warranty. The company states that the binocular went through several stages of testing before the instrument was finally packaged up for distribution. Both the ocular and objective lenses came with standard soft rubber caps which can be permanently affixed to the binocular. I was half expecting a lens cleaning cloth but none was provided.

The binocular has a very attractive appearance, with the optics housed inside a strong polycarbonate body overlaid by an anthracite-coloured, texturised rubber armouring. While I have used binoculars with magnesium alloy bodies before, I have not noticed any particular advantage of using metal bodies over their synthetic polymer counterparts, except perhaps to shave off some excess weight. But at 692g, this binocular is not exactly heavy. Indeed, surveying the market in 8 x 42 roof prism binoculars quickly reveals that the weight of the Kestrel falls into the median in the range for instruments of this specification.

The fetching anthracite colour of the binocular is beautifully complemented by the sky blue logo of the company and its ED billing inlaid on the top surface of the instrument. I’m not normally taken much aback by the cosmetic appearance of a binocular but I must admit to really liking the colour scheme of this instrument!

The Viking Kestrel has a rugged anthracite body with the company’s attractive sky blue logo inlaid on the bridge.

The binocular has a single centrally placed hinge that is reassuringly rigid. Once adjusted to get your particular interpupillary distance (IPD) right, it stays in place even when taken out of and placed back inside of its padded case.  Both the focus wheel and right eye dioptre are constructed from metal and coarsely stippled for maximum grip. The twist-up eye cups are of very high quality, rubber over metal that offer 3 positions. With a very generous eye relief of 17.5mm(measured), they afford very comfortable viewing for those who wear eye glasses and those who don’t. Most importantly, when clicked into place they hold their position very solidly, even after an undue amount of pressure is applied.

The underside of the body has two small thumb rests which allow your fingers to naturally gravitate towards when handling in the field. Overall, I found the Kestrel to be very ergonomically designed.

Details of the underside of the Viking Kestrel 8 x 42 binocular.

The focus wheel moves with what I would describe as slow-to-standard progression. There is a little bit of play in it which can sometimes result in over- or under- focusing, especially when imaging a fast moving object, but overall I felt it was perfectly adequate for most purposes one would use a binocular like this for. The wheel moves through 1.5 revolutions from its close focus to beyond infinity. Having a little extra focus travel beyond the infinity setting may not have any immediate advantages, but I’ve found that it is quite important when attempting to clean up the image at the periphery of the field. In other words, having a slightly longer focus travel can help alleviate some of the off-axis Seidel aberrations found on most any binocular image.

The objective lenses on the Kestrel have very nice and evenly applied anti-reflection coatings.

The attractive cyan coloured anti-reflection coatings on the Kestrel ED binocular.

What’s more, they are very deeply recessed – exceptionally so, I’d say. I measured them at a whopping 10mm – significantly deeper than any other binocular I have encountered. This affords exceptional protection against rain, and wind-borne dust and will also attenuate the build up of contrast-robbing dew.

The objectives of the Kestrel are recessed a whopping 10mm or so, helping to keep airborne dust, spray and dew at bay during field use.

All in all, I was well pleased with the ergonomics and physical presentation of the Kestrel, but all of that counts for nought if the optics are not up to scratch.

Mounting the binocular on a tripod is easy to do by unscrewing the stalk at the front end of the bridge, between the two barrels,and which enabled me to test the collimation of the instrument by observing well defined targets on a hillside a few miles distant, looking for both horizontal and vertical asymmetries in the images presented in both optical tube assemblies. To my relief, the Kestrel showed no misalignment issues.

Stray light tests

No roof prism binocular, no matter how well made, can perfectly stave off unwanted reflections, diffraction artifacts and diffused light when a very strong light source is directed inside the instrument Setting up my standard iphone torch light test, I was very impressed with the results I obtained with the Kestrel. I used two controls to compare the views with this instrument; my trusty Barr & Stroud Savannah(which exhibits excellent stray light control and very subdued diffraction spikes) and my superlative Leica Trinovid BCA 8 x 20 pocket glass, which, until now, offered the best results I have recorded in such tests.  Well, the Kestrel served up an exceptionally clean image, with very low unwanted reflections and an almost imperceptible diffraction spike. The result bested the Barr & Stroud binocular and was the equal of the Leica but with a far less obvious diffraction spike! Furthermore, just like my two binocular controls, diffused light was pretty much non existent.

Stray light control instruments: the Viking Kestrel (bottom) with the Barr & Stroud Savannah (top).

Further testing on a sodium street light confirmed the same results; the view through the Kestrel had well nigh perfect results with no annoying internal reflections, zero diffused light and no diffraction spikes! I did however detect rather strong off-axis flaring with the Kestrel, which was more pronounced than in the control binoculars, as evidenced by placing the street light just outside the field stop of the instrument.

The Viking Kestrel (top) tested against the Leica Trinovid BCA (bottom).

Overall, I was very pleased with the outcome of these stray light tests, which suggested that the Kestrel would likely deliver exceptionally punchy images, rich in contrast during normal daylight use.

Daytime testing

My first day of testing took place on an overcast June day. Examining some tree trunks a few tens of yards distant showed a very wide and wonderfully sharp and vibrant image. Compared with my Barr & Stroud Savannah 8 x 42, the colour tone was noticeably more neutral in the Kestrel compared with the very warm yellowish tones in the former. Within its large sweet spot, I judged the image sharpness to be a tad better in the Kestrel than in the Barr & Stroud. Examining the summit of a nearby hill against a bright overcast sky also revealed that the Kestrel was better corrected for chromatic aberration as judged by the absence of a very faint sliver of blue fringing at the boundary between the summit and the background sky. The achromatic Barr & Stroud did show that fringe in the same test.

That said, it soon became clear to me that the Kestrel was showing some lens flare in a portion of the image similar to what I had previously detected in my sodium street lamp test, reducing its contrast in comparison to my control binocular. This flaring could be removed by simply placing my hand over the objectives, blocking off some of the bright light from the sky above it. The flaring was also reduced by observing through an open or closed window under a roof but always reappeared once I re-emerged into the out of doors.

The flaring was only slight though and I suspect that most folk wouldn’t have even noticed it, but once you see it it’s very hard to ignore it, especially since the less expensive Barr & Stroud Savannah did not exhibit such behaviour. Examining the exit pupils showed up a significant amount of light leakage which you can see in the image below:

Some light leakage around the right exit pupil is apparent in this shot.

I decided that I would contact Viking Optical describing the problem I had encountered to see if they were willing to have a technician look at the binocular. So, I fired off an email to them, describing the problem as best I could, and within a few minutes they got back to me asking if I’d be willing to send them the instrument so that they could properly assess its performance. I agreed, so back went the binocular into its case and box for shipping down to Suffolk.

I will continue this review as soon as I receive word on its progress.

A Change of Heart

I spent the afternoon of July 2 2020 comparing and contrasting the views through my Leica Trinovid 8 x 20 with the Kestrel 8 x 42 as well as the Barr & Stroud in bright sunny conditions. I detected the same weak veiling glare in the Leica and the Barr & Stroud  as I did in the Kestrel. Indeed, truth be told, it was more severe in the Leica than in the Kestrel on the same test objects, which I think is caused by its complete lack of any recession of its objective lenses. It was however a little less intense on the Barr & Stroud, but in every case it could be eliminated by shading the objectives with my hand. So I reached the conclusion that it is I who was really at fault. I have come to expect too much and have learned to spot tiny imperfections in optical performance. Furthermore, those light leaks around the Kestrel exit pupil lie outside of where my eyes intercept the image, and so will have little or no effect on the performance of the binocular.

Absolute perfection just cannot be obtained no matter how well made the binocular is. I therefore decided not to bother Viking with my petty complaint and will email them tomorrow morning informing them that I do not wish to pursue this matter, as well as to congratulate them on designing an excellent glass at such a good retail price.

Methinks a large slice of humble pie for tea is in order!

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

An Aside: Veiling glare reported in the Leica Trinovid 8 x 20 binocular

A very bad case of glare in a Swarovski CL Companion 10 x 30

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

Tests on Light Transmission

As I described in numerous previous blogs, the Barr & Stroud Savannah 8 x 42 is an excellent wide angle binocular, especially for its very modest retail price(£120UK), but I understand that it does not have the brightest dielectric coatings on the roof prisms( they may be either silver or aluminium). I therefore expected the Kestrel to deliver brighter images in low light conditions. So I ventured out at dusk on the overcast evening of July 1st 2020 and began comparing the views in both the Kestrel and the Savannah. Starting at about 10.15pm local time and ending at 10:40pm, I conducted simple A/B tests on some tree branches about 40 yards distant,  evaluating the brightness of the image in the binoculars as the light slowly drained from the landscape. These tests did show that the Kestrel served up the brighter images, as I would expect if they had better coatings, but the difference wasn’t exactly night and day. It was only a little bit brighter at best, becoming most apparent toward the end of the testing than at the beginning.

Investigating Claims that ED Glass Produces Brighter Images

I was also able to conduct more tests to ascertain if the presence of ED glass produces brighter images than an instrument with no ED glass. To make the test as fair as possible, I needed a binocular with good dielectric coatings but without ED glass. So, I borrowed my son’s Celestron Trailseeker 8 x 32 which I reviewed in an earlier blog. This binocular does have those all important dielectric coatings on the roof prisms and is also fully multi-coated like the Kestrel ED binocular. Because the apertures are different, I made an aperture stop of 32mm diameter from cardboard and placed it over one of the 42mm objectives on the Kestrel as shown below:

The cardboard aperture stop placed over the aperture of the 42mm objective of the Viking Kestrel(lower right). Note the Celestron Trailseeker binocular at the left of the image.

On the same evening of July 1, I compared the images served up with the stopped-down objective on the Kestrel with those garnered by the full-aperture Celestron Trailseeker 8 x 32, using the same eye to examine both. Again I performed these tests at dusk, when the test tree branches some 40 yard distant were in deep twilight. The results were quite revealing! Conducting the same A/B testing as before, I concluded that there was very little difference in their perceived brightness. I did however give the nod to the Kestrel though, but only just!

This is the second test of this nature that I have conducted, with both results seeming to indicate that ED glass either does not confer brighter images, or, if it does, it’s marginal at best.

This is at odds with bold claims made by many sources in the online literature and is widely adopted as a marketing stratagem to sell binoculars to the public.

Like I stated before, it’s not so much the ED elements as much as the coatings that distinguish an average binocular from a great one!

Further Notes on Glare, its Causes & its Management

Our long summer days here in Scotland are a godsend, not only because they allow one to observe for longer durations in warm or mild weather but, as I’ve been discovering, they afford many opportunities to conduct experiments with my binoculars. Today proved to be a good day to get to grips with the glare I’ve been observing with my instruments. The afternoon was very bright and sunny but as the afternoon gave way to evening, the skies became very overcast again, so I was able to test out two very different binoculars – the Leica Trinovid and the Viking Kestrel – in these very different conditions. I now believe I have a better understanding of what causes glare in these glasses, and so, by extension, in all binoculars.

The first observation I have made is that glare is actually a lot less problematic during sunny spells than it is during overcast spells. When the Sun is shining in a sky with little cloud cover, the main light source i.e.the Sun, is concentrated in one direction and so long as you are not looking at something very near the Sun, relatively little or no glare is noticed. For example, when glassing tree trunks located at the edge of a strongly shaded copse, with the afternoon Sun illuminating it from the side, glare is very well subdued in both binoculars. This kind of glare manifests itself as a localised crescent or arc at the bottom of the binocular image with much of the rest of the field being largely unaffected. The worst culprit is the little Leica Trinovid, as its objectives have no protection from stray ambient light. The Kestrel does significantly better under the same conditions because its objective lenses are located at the bottom of a 10mm deep ‘well’ which acts as a very effective lens hood, a trick long known to photographers.

But under overcast skies, where strong summer sunlight is diffused by extensive cloud cover, glare becomes much more of a problem in both instruments and seems to be more spread out in the binocular image. Glassing the same tree trunks at the edge of a shaded copse produces noticeably lower contrast images than under sunnier conditions; even when glassing near the Sun. The reason for this must be due to the fact that in the open air, under overcast conditions, with a bright sky overhead, there are many more locations where the light can reflect off the spacers between the objective lens elements at the bottom of the binocular objective, which in turn causes this flaring to spread out or diffuse across the binocular image, reducing contrast in a more noticeable way. This is referred to as veiling glare. So overcast skies appear to produce greater damage to the image because it has a greater potential to affect the entire field than much more localised crescent glare observed in clear sunny conditions. What is more, bigger glasses, which collect more light will show this type of glare well into twilight, whereas in smaller glasses which can’t collect as much light, the same glare can’t be seen!

Consulting a birding forum, I was able to verify this and I also learned that even alpha binoculars suffer from this problem. The poor chap was complaining about glare on his maiden voyage with his fancy new Zeiss Victory FL 8 x 42 and more knowledgeable glassers were able to chime in and offer some detailed explanations and a hefty dose of sympathy for good measure!

Three points to summarise all of this:

  1. The worst effects of glare can be removed by simply shielding the binocular objectives from the offending light source using your hand.
  2. Glare is a fact of life for most any glass, from the most humble to the most advanced. It’s par for the course and we must accept it and move on!
  3. Glassing under the canopy of a forest or in an observing booth with a roof over your head, or even donning a broad-rimmed hat will all but eliminate the worst effects of glare.

Further Notes on using the Viking Kestrel in the Field

Saturday July 3 2020

After a day of heavy rain, the clouds cleared off in the evening, leaving a tranquil blue sky. It was the perfect opportunity to go for a long walk around the picturesque Culcreuch Castle Estate with the Viking Kestrel 8 x 42. The instrument feels very solid in my hands and its fine mechanics work flawlessly. The quality padded neck strap with the company’s fetching colour logo proved very comfortable to use.  I stopped to say hello to a pair of Mute Swans and their family of five cygnets at Culcreuch Pond. The binocular served up beautiful, pin-sharp, views of the pure white plumage of the adults wonderfully contrasted with their rusty orange beaks and jet black foreheads. The cygnets had almost lost their fluffy down feathers by now and had developed their attractive tawny drapery, which stood out well against the sullen waters beneath them. And though the surface of the pond dappled in strong reflected sunlight, the binocular served up flawless images with incredible contrast and no annoying reflections.

Ambling up the path a little further, I enjoyed a fascinating fifteen minute excursion watching a group of Swallows perform their incredible feats of aeronautics (far more advanced than any human made flying machine) swooping and gliding with great speed and agility, gorging on low flying insects along a large grassy lawn immediately in front of the castle. The Kestrel proved to be a magnificent instrument to follow them, with its very large and well corrected field of view. Their prominent forked tails, iridescent blue-black upper body and almost comical, chocolate-brown faces could easily be made out as they flitted across the field of view. A lady out walking her dog, obviously curious about my glassing, stopped to tell me that a few big storms had threatened these migratory birds earlier in the year, reducing the numbers reaching our shores from Africa. It put a big smile on her face to see that it was business as usual for these noisy summer visitors!

These experiences convinced me that the Viking Kestrel 8 x 42 will make an excellent birding binocular with its superb contrast, sharpness and colour correction, not to mention its super-comfortable twist-up eye cups, generous exit pupil size and smooth focusing wheel.  As I continued to walk, I enjoyed glassing the intense colour of mature green leaves drenched with life-giving rains that made them glisten intensely in the early evening sunshine. I almost lost myself observing the intricately textured bark high up in their canopies against a gorgeous blue sky beyond. That said I must also report that there is very mild pincushion distortion at the edge of the field but certainly not enough to cause any alarm.

After sunset I ventured out again to catch a nearly full Moon skirting low in the south-southeast at about 11pm local time. To get a good unobstructed view I had to take a walk about half way up Culcreuch Castle Road. But it was worth it. The almost full Moon in all its glory hovered just above the tree line beyond a gently sloping hill, its low altitude imparting a yellowish cast to its normal pale silver countenance. The image served up in the Kestrel was gorgeous, pin-sharp across almost the entire field, with beautiful contrast and nary a sign of any internal reflections. This will make an awesome Moon glass! As usual, I noted that the Moon remained sharper when glassed horizontally than vertically; again very normal behaviour for a binocular.

Round about a quarter to local midnight, the sky had gotten sufficiently dark to make out the familiar asterism of the Plough high in the northwest. This afforded a perfect opportunity to estimate the size of the field of view. Well, I was able to hold Phecda and Merak in the same binocular field, which I estimated to be 7.9 angular degrees apart, with a tiny sliver of open sky available before it reached the field stop. Thus, I was confident that the quoted 8.1 angular degree field stated in the specifications was accurate. What is more, I glassed the bright orange star, Arcturus, high in the west-southwest, carefully examining the sharpness of the stellar image as it moved from the centre of the field all the way to the field stop. The results were good here too; Arcturus remained nice and pin sharp across most of the field with only the outer 10 per cent showing significant distortion, but there was no ballooning of the star like some inferior models I’ve glassed with in the past. That said, I was still able to play with the focus a little to tidy the image up somewhat at the edge of the field. All in all, I came away convinced that this would make an excellent star gazing glass. I can’t wait to use it later in the summer when truly dark stars return to our shores.

A most impressive performer.

Conclusions

There are good reasons why the 8 x 42 configuration is considered the darling glass for twitchers, hunters and general nature observers. The extreme comfort with which it meets with your eyes, moderate weight and great low light performance are just a few reasons why they have proven so popular. The Viking Kestrel 8 x 42 is packed full of hi-tech optical features and has very solid mechanics that will ensure it will serve you well for many years. The quality of the image is so good that it will rival those served up by models costing many times more. Indeed, if you’re saving up for a premium glass, I would strongly recommend you try this model first.  It could well be all the binocular you really need!

As you can see from reading the string of reviews posted at the beginning of this blog, the reviewers were unanimous in their praise of this extraordinary binocular, and for a retail price of just over £200 UK, it represents exceptional value for money.

It really is a steal!

Viking Optical also has a solid reputation for repairing binoculars and this is yet another reason why it is an attractive option for British glassers in particular. If something should go wrong with your Viking binocular, you can be confident that their technical staff will repair it if it’s under warranty or, failing that, for a reasonable fee.

The Viking Kestrel 8 x 42.

Highly recommended!

 

 

Neil English is an avid glasser and telescopist who is firmly on the side of the money conscious consumer. If you like his work, please support him by buying one of his books. Thanks for reading!

 

De Fideli.

 

A Short Commentary on the Christian Standard Bible(CSB).

The Christian Standard Bible(CSB) by Holman.

The word of the Lord that came to Joel son of Pethuel:

Hear this, you elders;

listen, all you inhabitants of the land.
Has anything like this ever happened in your days
or in the days of your ancestors?
Tell your children about it,
and let your children tell their children,
and their children the next generation.
What the devouring locust has left,
the swarming locust has eaten;
what the swarming locust has left,
the young locust has eaten;
and what the young locust has left,
the destroying locust has eaten.

                                                                     Joel:1:1-4

 

In 2017, Holman Bible Publishers brought out a brand-new English translation of the Holy Bible – the Christian Standard Bible(CSB) – which represents an updated version of the Holman Christian Standard Bible(HCSB), first published back in 2004. The CSB promises to be highly accurate to the original koine Greek and Hebrew of the original texts, but also to be highly readable.

Tune in soon to see whether or not the CSB has achieved its goals.

 

De Fideli.

Product Review: Pentax Papilio II 6.5 x 21.

The little butterfly binocular; Pentax Papilio II 6.5 x 21.

June 19 2020

 

Binocular: Pentax Papilio II 6.5 x 21mm

Cost: £109.00 delivered

Optics: Reverse Porro /patented converging objectives for ultra-close focus

Coatings: Fully Multi-coated

Exit Pupil: 3.23mm

Field of View: 7.5 degrees (132m @1000m/ 323ft@1000yards)

Focus Range: 18 inches to infinity

Eye Relief: 15mm

Weight: 290g

Tripod Mountable: Yes

Dimensions: 11.0 x 11.4cm(W/H)

Nitrogen Purging: No

Waterproof: No

Accessories: High quality neck strap, rain guard, carry case, instruction manual and warranty card.

Life is full of surprises; some good and some bad. I’m happy to report a surprise of the pleasant variety in this review, featuring the Pentax Papilio II 6.5 x 21 binocular. Though it’s been on the market for several years now, it fell below my radar partly because I became rather fixated with high quality roof prism binoculars and never considered the old classic designs using porro prisms.

Porro prism binoculars are easier to make well in comparison to their roof prism counterparts. They are also considerably less expensive compared with roof prism models of similar quality. To some, their fall from grace in recent years was not due to their inferior optical quality, but more to their larger size and ‘outdated ergonomics.’ That said, they still have a loyal following among those who appreciate fine optics.

In my recent survey of the pocket binocular market, being somewhat dismayed by the lack of credible user reviews,  I went on a shopping spree to test out literally dozens of models – all from the roof prism variety – learning that in general, you get what you pay for. But there is always something new to learn and over the last few weeks I’ve been putting this tiny little binocular through its paces.

And it’s been a revelation!

The name ‘Papilio’ derives from the Latin for butterfly. Pentax were the first company to design these reverse porro binoculars featuring a patented converging objective system that allows these instruments to focus on objects as close as 18 inches – way closer than any roof prism binocular can do. The design was an instant success and thousands of nature enthusiasts snapped them up to provide wonderful stereo-microscope-like views of flowers, leaves, insects  etc. The first generation models had a few shortcomings though, as the literature is awash with reports that the anti-reflection coatings were not up to scratch. Experienced glassers reported bright reflections off the eyepiece field lenses and annoying internal reflections, cutting down on contrast and increasing glare in strongly back-lit scenes. Some resourceful users reported ways of reducing some of these annoying shortcomings however, such as using a broad-rimmed hat to cut out peripheral glare for example, or using them in deeply shaded areas where the contrast-robbing deficiencies in the coatings were less obvious etc. Others just accepted their shortcomings and simply enjoyed them as specialised, close-focus devices to study the complexities of the creation.

But then Pentax brought out a second generation Papilio featuring much improved anti-reflection coatings on all glass surfaces. Called the Papilio II, they are offered in two models; a 6.5 x 21 and an 8.5 x 21. Being the proud owner of a superlative 8 x 20 pocket glass by Leica, I was more interested in the lower power 6.5x model, as it seemed to be the least compromised of the two and would also offer me a larger exit pupil, which is both easier to operate in general use and would prove superior to the 8.5x model in low light situations at dusk or dawn, or on heavily overcast winter days.

First Impressions

The Pentax Papilio II package.

The binocular arrived double-boxed and contained the binocular, a nice faux leather case, a high quality neck strap, a rain guard covering the ocular lenses, operating instructions and a warranty card. A quick examination of the instrument revealed that all was well; the eyepieces could be extended with a click, the focuser worked smoothly, as did the right eye dioptre ring, and the objective lenses housed inside an optically flat glass window were spotless.

To ocular end of the Pentax Papilio II 6.5 x 21 binocular.

The padded neck strap was a breeze to attach. because it has built-in clips. All one need do is push them through the two holes on the side of the instrument where they are held firmly in place. What a delightful change from threading the strap through tiny little lugs!

The body seems to be made of ABS plastic and covered in a thin layer of texturised rubber which affords excellent grip while manhandling. The double hinges are quite stiff and once the optimal IPD is set, they stay in place. The underside of the binocular has neat little thumb indentations which makes holding it a wee bit easier.

The under side of the Papilio II has thumb indentations for easy handling in the field.

The dioptre ring also served up a pleasant surprise. Instead of rotating smoothly and silently either clockwise or counter-clockwise, this dioptre has click stops that you can hear as you rotate it. At first I was a little concerned that it may not offer the precision of a smoothly rotating right eye dioptre ring, but my wife and I were able to adjust it to accommodate our different settings easily and accurately. Just like some premium roof prism binoculars which have a built-in click stop dioptre, the low cost Papilio II offers the same security against accidental movement. A very clever engineering solution!

The eyecups are plastic and covered in soft rubber. They offer three positions; fully down(for eye glass wearers) or two clicked up positions, affording a maximum eye relief of 15mm. To my relief, I found that they hold their positions very rigidly and work well in field use.

I was also very impressed with the large textured central focus wheel, which moves quickly and very smoothly with no backlash. It has a very large focus travel though, requiring 3 full rotations going from its closest focus at 18 inches right out to infinity. Good focusers are an essential feature of a binocular and I felt Pentax went that extra mile to make sure it worked well.

The objectives are housed behind an optically flat window which also has good anti-reflection coatings applied to it in order to ensure high light transmission and minimise glare. At first I thought the window would be a negative addition, as it might have introduced more unwanted reflections than I bargained for, but as you shall see shortly, I need not have worried!

The optically flat glass window protecting the moving objectives is anti-reflection coated, helping to keep contrast high in the final image.

A straight through look shows the objectives behind the glass window. Note the low reflections off the window itself.

Another really neat feature of this Pentax Papilio II binocular is the in-built thread on its underside that allows it to be mated to a tripod for more exacting work. This is a rare feature on instruments this size but I can think of many situations – both in the great outdoors and in an indoor studio – where it could prove very beneficial. What a super nice touch!

Note the built in tripod-friendly thread on the underside of the binocular.

A quick look through the instrument instantly impressed. The image of a tree trunk some 50 yards distant was bright, tack sharp and very high in contrast. I was also impressed by its wide field of view – 7.5 angular degrees ain’t too shabby! But I was literally blown away when I focused in on a flower bed of Johnson’s Blue Geraniums sat just outside my front door. Wow! The view was quite simply astounding! Placing myself just 2 feet away, the sharpness and colour fidelity of the image was excellent and the level of detail seen within the individual flowers was mesmerising!

Stray Light & Glare Test

But I took heir of myself and proceeded to test the binocular in my usual ways. So first I set up a flashlight test in my living room, by setting my iphone torch setting to its highest(read brightest) level, and standing a few metres back, I aimed the binocular into the intensely bright light beam. Wow! The result was excellent! Compared to a few high quality control instruments (all roofs), the Papilio II showed a few very minor, green coloured internal reflections with no diffraction spikes and no diffused light. Comparing it to my Zeiss Terra 8 x 25 pocket glass, the reflections in the Papilio were only slightly stronger but without any diffraction spikes. Indeed, diffraction spikes are almost a universal feature of roof prism binoculars, however well built, but porro prism instruments seem to be devoid of these. Even the venerable Leica Trinovid BCA 8 x 20 showed an obvious diffraction spike in the same test though its internal reflections were better suppressed than in the Papilio II.

The Pentax Papilio II 6.5 x 21 has excellent control of stray light, as compared with a top-performing Zeiss pocket glass costing nearly three times more!

Later in the evening, when the sodium street light came on, I once again compared the Papilio II and the Zeiss pocket glass. As expected, the Papilio II delivered excellent results; very subdued reflections and no diffraction spikes. As a glasser who cannot stand excess glare and internal reflections, I was thoroughly delighted with the results I obtained from this low-cost binocular.

So far so very good!

Collimation Test

Collimation checking and right eye dioptre adjustment are best done on a tripod.

By affixing the Papilio II to a tripod, it’s easy to check the collimation of any binocular. Aiming at the hilltops a couple of miles distant, I checked the field of view both horizontally and vertically in both barrels. The results showed very slight horziontal misalignment( as evidenced by a slight asymmetry in the edge of field views) but perfect vertical alignment. I deemed the result quite satisfactory.

A tripod-mounted binocular is also a good way to tweak the right eye dioptre by focusing on the writing on a council notice affixed to a lamp pole some 40 yards in the distance. The dioptre ring clicks as it moves clockwise or anticlockwise making it real easy to get the optimal sharpness in the right barrel when it is locked rigidly in place.

Optical Tests

I conducted my optical tests under a variety of conditions, ranging from bright afternoon daylight in the open air, shaded areas underneath the canopy of trees while walking around in a copse, performance at dusk and finally looking at some bright stars in a twilit June sky around local midnight.

Comparing the performance to my Zeiss Terra 8 x 25 ED, I was very impressed with the optical performance of the Papilio II 6.5 x 21. To my eye, the images of textured tree trunks looked equally sharp in both binoculars, with the Papilio displaying the wider field of view at a smaller image scale. Contrast was excellent in both instruments, which both sport very large sweet spots, and only showing slight softening at the extreme edge of the field. The Papilio features aspherical ocular lenses which keeps off-axis aberrations at bay. In this respect, the Papilio II produced less field curvature(as evidenced by aiming at a telephone pole a few tens of yards distant and moving the pole to the edge of the field) than the Zeiss. Indeed, I pulled out my wife’s Opticron Aspheric LE 8 x 25 which also sports aspherical ocular lenses and displays superior edge sharpness to the Zeiss Terra, as reported in a previous blog. Well, the Papilio II proved fully the equal of the Opticron pocket glass on the same target!

The Pentax Papilio II 6.5 x 21( left) and the Opticron Aspheric LE 8x 25 (right).

Under the brightest daylight conditions it is easy to detect reflections off one or more of the ocular lenses as this manifests as a subtle circular glare disc covering much of the field. Alas, these annoying reflections are all too common on a lot of instruments that skimp on their application of anti-reflection coatings. I was very pleased to see that the Papilio II also passed this test with flying colours – that is, it was not present. Chromatic aberration was pretty much non-existent even when pointed at a tough target like a television aerial against a bright overcast sky.

Comparing the Papilio II to my Zeiss 8 x 25 roof prism binocular under the shade of  conifer trees near my home, I found both binoculars to yield up equally bright and sharp images of ground vegetation just a few metres away. When I did the same tests with the Opticron, I felt the Papilio served up slightly brighter images although the sharpness was judged to be more or less the same.

Going out at dusk around 10.15 pm, I compared the brightness of the images of tree branches about 50 yards distant served up by the Pentax Papilio II, the Zeiss Terra ED 8 x 25 and my Leica Trinovid 8 x 20. The Papilio II and the Zeiss pocket glass threw up images that were about equally bright, with the nod going to the Zeiss ( but only just!). Comparing the Trinovid 8 x 20 to the Papilio II in similar tests showed that the images were noticeably brighter in the latter instrument.

The Leica Trinovid BCA 8 x 20 (left) and the Pentax Papilio 6.5 x 21(right).

All in all, these were excellent results showing that the light transmission efficiency of the Papilio was very good indeed based on Zeiss’ published data on the Terra glass, which has 88 per cent transmission. The dimmer images served up by the Trinovid was easily explained in terms of its smaller exit pupil (2.50mm compared with 3.23mm).

My final optical tests were conducted under a twilit night sky ’round about local midnight. I aimed the binocular at the bright summer star, Vega, and compared the views in both the Zeiss and the Papilio II. Both instruments focused Vega down to a crisp, white pinpoint that held its sharpness across nearly all of the field. Moving the instruments horizontally showed better off axis performance than those exhibited by moving the star up and down, to the top and bottom of the field, respectively. The only difference I could detect was the darker sky hinterland in the 8 x 25 Zeiss pocket glass, perhaps owing to its higher magnification.  But even so, the differences weren’t huge.

These tests convinced me that the Pentax Papilio II 6.5 x 21 has excellent optics, especially for its very modest price tag. Its simpler design to roof prism binoculars means it has less optical components overall, and the combination of aspherical ocular lenses, high quality Bak 4 prisms and fully multi-coated optics all contribute to this high optical field performance.

Further Notes from the Field

Using the reverse porro prism designed Papilio II takes a bit of getting used to. At first, its strange body shape reminded me of a scene from a Star Wars Movie when Luke Skywalker used weird looking binoculars to monitor the movements of marauding Sandmen lol. That said, it’s quite easy to hold steady and most anyone can use it, including kids.

Though it is just as lightweight and portable as a pocket binocular, it doesn’t fold nearly so compactly as a dual hinged pocket glass like the Zeiss Terra 8 x 25, as shown below:

Though it weighs just as little as a light weight pocket binocular like the Zeiss Terra 8 x 25(bottom), it cannot fold up quite so small but will fit in a large coat pocket or a ruck sack.

The Pentax Papilio II 6.5 x 21 can be used as a decent birding binocular, with its quality optics and fairly large and very well corrected field of view.  Its super-fast focus wheel also helps in this regard. One drawback of its lower magnifying power compared with more conventional glasses (which almost invariably use powers of 7x to 10x) is reduced range. Sometimes you just need 8x or 10x to bring the subject sufficiently close in order to get a good view of it. And 6.5x may not be the best choice for a twitcher, where the subject is heavily camouflaged, small or located at a lengthy distance from the user. For close-range work (read within a couple of hundred yards) it should work well though. Its small aperture will also limit its use to bright daylight conditions most of the time, and thus will be less suitable for work when lighting is compromised, such as at dawn or dusk, in which a larger aperture glass would serve you better.

The instrument is absolutely head and shoulders above any other instrument on the market if your speciality is close-up work, like studying insects, flowers, rocks and minerals. It will also prove indispensable to artists who paint still life scenes indoors, where the instrument can be permanently mounted on a clamp or tripod, where the subject can be examined in exquisite detail under optimal lighting conditions. It also serves as a very effective stereo microscope, affording very comfortable and immersive views of a wide variety of subjects.

I have noted that for such close-up work, the Papilio II 6.5 x 21 seems to provide greater than advertised magnification. When viewing flowers at 18 inches, for example, the power seems closer to 7.5x or 8x and not the advertised 6.5x. This is probably true of the 8.5 x 21 instrument as well, where a power of 10x or more might be expected during these close-range observations.

The binocular is not weather or water proof, which might be a negating factor in choosing it for general purpose viewing or bird watching. In cold weather, it will fog up when brought from the outside to a warm indoor room. I would not recommend using the instrument in rainy or showery conditions. But there are ways to protect it from fogging up internally. For example, by placing the instrument back in its case with the rain guard on prior to bringing it indoors is a good move, as would storing the instrument with an effective desiccant, like silica gel, will help keep moisture at bay and prolong its shelf life, especially if you live in humid climes.

The instrument is not really recommended for astronomical use, though it will serve up very nice news of illuminated cityscapes owing to its good control of stray light within the optical train. That said, it ought to serve up nice images of the Moon and bring some of the brighter deep sky objects into view from a dark, country sky.

I have noted that the optically flat glass window protecting the objective lenses is a magnet for attracting pollen. Not a big deal in the scheme of things, but something to bear in mind. You’ll need a soft lens brush to keep the window clean. I tend to give it a brush down after any prolonged spell(more than 30 minutes or so) outdoors.

The glass window protecting the objective lenses attracts a lot of pollen so will require regular brush down after prolonged field use.

Another niggle reported by some users of the Pentax Papilio II binoculars is that the supplied carry case is too small to comfortably house the instrument when the neck strap is attached. And while removing the strap is one solution, it might not be to the liking of some individuals who wish to use it in the spur of the moment. I have found a solution of sorts, by placing the binocular in the case while feeding the two ends of the strap out from both ends of the case cover. The strong velcro seal is plenty strong enough to hold the binocular in place inside the case and the straps can be used to carry it about!

The neck strap can also double up as carry strap for the case & binocular.

As always, I store the binocular inside its case with a sachet of silica gel and store it in a cool( 60 F), dry and well ventilated pantry to protect against fungal infestation.

Conclusions: The Pentax Papilio II 6.5 x 21 was a very pleasant surprise. For its modest cost of just over £100, you get very decent classic porro prism optics with unbeatable close-focus capability. I think every binocular enthusiast should own one! Far from being a one-trick-pony, it will serve as a very versatile instrument for casual viewing, nature study and bird watching. Just understand that it can’t be used in rainy conditions and needs protection from internal moisture build up in humid climates requiring extra care when storing for long-lived use.

Highly Recommended!

Neil English is the author of seven books in amateur and professional astronomy. If you like his work, please consider purchasing one of his books. Thanks for reading!

De Fideli.

What I’m Reading.

Formulating dynamite arguments against atheists from one of the world’s leading Christian apologists.

Title: Stealing From God: Why Atheists Need God to Make Their Case.

Author: Frank Turek PhD.

Publisher: NavPress(2014)

ISBN: 978-1-61291-701-6

Paperback, 269 pages.

Price: £11.99

About the Author:

Frank Turek is the president of CrossExamined.org, a dynamic speaker, and a Gold Medallion award-winning author who has written/cowritten several books, including I Don’t Have Enough Faith to Be an Atheist (over 200,000 sold).  He hosts an hour-long apologetics TV program (broadcast on the NRB Network into 32 million homes) and an hour-long apologetics radio program (broadcast on 144 stations).  Frank speaks over 100 times a year at colleges, high schools, and churches.  He has debated several prominent atheists, including Christopher Hitchens and David Silverman. Frank is also an adjunct professor of apologetics at Southern Evangelical Seminary.

 

If you think atheists have reason, evidence, and science on their side, think again. Award-winning author Dr. Frank Turek (I Don’t Have Enough Faith to Be an Atheist) will show you how atheists steal arguments from God when trying to justify their atheism. If that sounds contradictory, it’s because it is! Atheists can’t make their case without appealing to realities only theism can explain.

In an engaging and memorable way, Stealing from God exposes the intellectual CRIMES atheists are committing. Join Turek as he explores how many atheistic arguments, instead of disproving God, show that God actually exists. Turek also provides a powerful four-point defense for the truth of Christianity. Whether you are exploring answers for yourself or want to understand how God transcends the reasoning of those who would deny His existence, this book is for you.

 

Endorsements:

 

As a journalist at the Chicago Tribune, I covered some horrific crimes that helped cement me in my atheism. I didn’t realize that I was committing a series of intellectual crimes by stealing from God in order to argue against Him. Frank Turek brilliantly exposes these C.R.I.M.E.S of atheism in a way that you’ll never forget.

Lee Strobel, bestselling author of The Case for Christ and Professor at Houston Baptist University.

Frank Turek in his usual inimitable, user-friendly style presents a highly accessible case for the falsity of atheism and the truth of Christianity. This book provides powerful and clear answers to questions of enduring importance for every thinking person.

Dr. John Lennox, Professor of Mathematics at Oxford University

One of the reasons I love Frank Turek and his work is that he unapologetically  takes his case for Christian apologetics and aggressively to the New Atheists, Stealing from God dismantles the fragile premises of atheists’ ‘articles of faith,’ and, in the process, establishes an unassailable  case for the truth of Christianity. This book comes at precisely the right time when New Atheists are trying their best to undermine the Christian worldview and purge it from our culture.

David Limbaugh, New York Times bestselling author of Jesus on Trial.

 

I’m a big fan of I Don’t Have Enough Faith to be an Atheist but Stealing from God is Frank’s best book to date. Meticulously researched and carefully argued, it shows that the atheists who argue that he doesn’t need to rely on God actually needs God to make that very argument. This book is an effective tool for reaching committed atheists because it demands that the atheists abide by the same standards they impose on others.

Dr. Mike Adams, Professor of Criminology at UNCW, columnist at TownHall.com and author of Letters to a Young Progressive.

 

De Fideli.

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

Well, I do hope that amateur astronomers will embrace this new book and, over time, to learn to love Newtonian reflectors as I now do. God willing, the book will be published in the late spring or early summer 2021.

Thanks for your attention.

Sincerely,

Neil English.

 

 

De Fideli.

 

Adventures with a Pocket Binocular Part II.

A work commenced November 11, Anno Domini 2019.

Part II

Subject to Copyright. Completed text will cite references & bibliography .

 

 

Taming a Flame

Caveman’s telly.

The second week of February 2020 brought cold and tempestuous weather to Britain, with the arrival of Storm Ciara. Just as we were preparing our family evening meal on Sunday February 9, the storm caused a power cut which left us and our fellow villagers without electricity for a few hours. So out came the candles and on went the coal fire to keep us out of total darkness and comfortably warm. I have always been somewhat in awe of fire and fetched my pocket glass to observe the cadence of its flames as they rose upwards into the chimney column. Because of their excellent close focus, my pocket glasses can entertain me as much indoors as they can out of doors!

As I drank up the wondrous display of light and colour of the coal fire from the comfort of my couch just a few metres away, my mind reflected on the importance of fire to the progress of humanity over the milennia. Nature not only produced the fuels but also the reactive gas(oxygen) needed for fires to occur. They are thus vital components of a life-bearing planet. With an atmosphere of 21 per cent oxygen, it is just right to allow fuels(reduced carbon substrates) to ignite and generate heat and light. If the percentage of oxygen in our atmopshere were only a little higher, spontaneous combustion would be much more common and many areas of the world would experience the devastating effects recently suffered by the people and biota of Australia. If the oxygen levels were lower, we would be unable to extract enough chemical energy from food to allow us to do much in the way of higher cognitive activities such as talking, calculating and praying.

The unique ability of humans to create and control fire is probably the single most important activity that launched the high technology societies in which we now live. In its basic form, it provided our hunter-gatherer ancestors with warmth and light on cold winter nights, which allowed us to work for longer and so boosting human productivity. Its intense heat protected us from hungry predators stalking us out in the dead of night. By cooking food, it killed germs that might have made us sick. The intense heat of the fire also helped break down hard-to-digest foods, enabling us to extract their nutrients more effectively. With fire, humans could greatly expand the varieties of territories we could eke out a living in. No longer were mountains and frozen northern wastelands verboten. Fire must have triggered the largest exodus of humans from the warm grasslands of East Africa/Middle East, where we probably first emerged from after our forced expulsion from the Garden of Eden.

Our innate capacity to experiment led to further discoveries allied to fire. We learned to ‘cook’ wood, yielding the amazing substance we now call charcoal, and with that we could generate temperatures far in excess of any normal fire(up to a 1000C in fact!). Charcoal is a wonderful reducing agent, empowering our distant ancestors with the ability to ‘pull’ metals from ores; copper, tin, lead and the creation of alloys like bronze. Once we understood how to use air to increase the temperature of furnaces, the extraction of iron finally became possible. The age of metallurgy was born and with it the great transformation of our lives. Without a knowledge of combustion, we would have no ceramics, no cars, buses or trains, no computers, iphones or tablets; no skyrockets to scale heaven.

And no glass to peer through!

My binoculars would not exist were it not for fire!

And yet there are still deeper things to ponder. Why, for instance, doesn’t the coal I fetch from our bunker not react with the oxygen that surrounds it? Why, as creatures who ‘slow burn’ our food, do we not burst into flames? The answer is not all obvious, but pertains to the stability of both oxygen and coal at ordinary terrestrial temperatures. To burn coal, I must elevate its energy enough to initate the reaction, that is, by igniting the coal with a spark. And deep inside the countless trillions of cells that comprise the human body, enzymes(biological catalysts) lower the activation energy enough for our reduced foodstuffs to react with the molecular oxygen delivered to our body cells via myriad haemoglobin molecules.

But our ability to tame a flame is also related to our physical size. Think on it: if we were as small as a mouse say, we would be unable to get close enough to a fire to keep it fuelled without getting seriously injured. We’d also lack the muscle power to bring enough fuel in the form of chopped wood or dry brush to sustain the same fire. But humans are large enough(1.5 to 2m), and endowed with long enough arms with an ingenious manipulative tool at their ends(fingers with an opposable thumb), and with muscles powerful enough to chop and carry wood and lay it on a fire with outstreched arms, so keeping a safe distance from its desctructive flames.

And if we were significantly larger, gravitational forces would put much higher strains on our limbs. Carrying anything would much more difficult. Biophysicists have long known that simple power laws govern how body weight and limb strength scale with increasing height. Weight scales as the cube of height, but limb strength only scales with the square of height. That means that if we were much taller, strenuous physical activities would become far more challenging and even downright dangerous. Our limbs would shatter under their own weight and fumbling Prometheus falling into a fire would be a distinct possibility. The same principles explain why, upon faltering in a similar situation, a little child would emerge unscathed.

Can our physical size and the chemical and physical properties of our atmosphere that allow fires to be tamed and pressed into service by our kind be just coincidence? Is this just another serendipitous chain of events that happened to occur on our planet? Most certainly not! The godless naturalists can provide no credible answers to these questions.

They are, quite literally, left in the dark!

On the otherhand, a Creator God – an Unquenchable Fire – who designed this world for His human imagers to transform its natural resources seems far more probable to my mind.

Come, let us bow down in worship,
let us kneel before the Lord our Maker;
for he is our God and we are the people of his pasture,
the flock under his care.

Psalm 95:6-7

A Worthy Upgrade

The Leica Trinovid BCA 8 x 20 pocket binocular package.

During the first two weeks of January 2020, I had the opportunity to test drive a Leica Trinovid BCA 8 x 20 pocket glass kindly lent to me by a fellow villager. You can read about my opinions of that instrument here. As that report shows, I was very impressed with its wonderful optical and mechanical quality, but still a little concerned about how much use I would realsitically get out of a glass with very small, 20mm objective lenses. After some cogitation and deliberation, I decided that having two 8 x 25 units(the Opticron Aspheric LE WP and the Zeiss Terra ED) could not be justified, and so I gifted my Opticron to my next-door neighbour and invested in what is arguably one the highest quality achromatic(read non-ED) pocket glasses money can buy. Conducting some price comparisons across the internet, I managed to track down a UK-based seller offering the Trinovid for a very good price and I pulled the trigger.

The package arrived in perfect nick. What I received(see photo above) was a small box (actually double-boxed) with the Leica binocular safely packed inside a soft but rather oversized carry case, a small neckstrap, a comprehensive user manual, a test certificate and a booklet containing details of its 10-year warranty. The binocular had no eyepiece or objective lens caps though, and not even so much as a lens cloth thrown in for good measure!

My neighbour was thrilled to bits to accept the Opticron – a high quality pocket glass  – but I was equally thrilled to finally own arguably one the smallest, useful pocket glasses in existence. And, as my subsequent tests showed, the little Leica proved to be every bit as good as the unit I tested a few short weeks ago.

The little 8 x 20 Leica passed my flashflight tests with flying colours; it was just as clean and devoid of internal reflections as the earlier unit I investigated and delivered pin sharp images rich in contrast almost from edge to edge. There is no question that the quality control on these high-end pocket glasses is remarkably consistent. Optically, the Leica Trinovid BCA 8 x 20 is unquestionably a step up from the Opticron in terms of sharpness and contrast. Indeed, it is right up there with the Zeiss Terra 8 x 25, but in smaller, more elegant frame.

Once I had done my testing, I registered the instrument on Leica’s sports optics website(the serial number being printed under the right eyecup).

The Leica Trinovid BCA 8 x 20(left) has a smaller frame to the Zeiss Terra ED 8 x 25 (right).

As much of my work on telescopes over the last decade has involved raising amateur awareness of the wonderful properties of well-made achromatic refractors, I was thrilled to see that a top company like Leica was creating state-of-the-art miniature binoculars using traditional crown and flint glass. It showed me once and for all that excellent binocular optics doesn’t necessarily require the use of low dispersion lenses. Rather, it’s more to do with the precise figuring of the glass, as well as the application of state-of-the-art coatings to all optical surfaces that delivers this degree of excellence.

Both the Zeiss and the Leica are endowed with similar, high-quality optics, but one has ED Schott glass (the Zeiss) comprising one or more of its objective elements, while the Leica does not. But if I were to make an aperture stop for the Zeiss, reducing its effective aperture to 20mm, I would in effect have two instruments operating at 8 x 20 and with the same exit pupil(2.5mm). So the biggest difference between them would be the ED component and that would allow me to investigate claims made by a number of individuals over the years; specifically in relation to the brightness of the images served up by ED and non-ED optics. Is there any or much truth in this claim?

So I set to work performing some experiments in low light conditions, carefully comparing the images served up by both pocket glasses. I hope to report back on this in a later post.

A Better Case for a New Pocket Glass

The Leica binocular came with a soft padded case that was too large to fit it well. As you can see from the image below, the binocular has quite a bit of wiggle room inside the case and even when it’s closed, dust can easily enter and accumulate over time. This is especially the case(lol) as the instrument was not supplied with endcaps to cover the ocular and objective lenses.

The Leica logoed soft carry case is too large to fit the little Leica 8 x 20 and is not a very good deterrant against dust when the binocular has no dust caps.

I felt that there must be a better solution to this storage problem. So, after taking into account the dimensions of the Leica glass, I searched online for a suitable replacement. Eventually, I came across a tiny clamshell case, similar to the one I received with the Zeiss Terra but smaller again. Here is what it looks like:

A tiny, anti-shock clamshell case that zips shut.

Here is another photo of the clamshell case compared with the original case for reference:

The Clamshell case is significantly smaller than the supplied Leica soft padded case.

Costing just £6.99 inclusive of delivery, the clamshell case is shockproof and can be zip-closed.

The clamshell opens up revealing the storage space inside. Note the sachet of silica gel.

To my relief the Leica binocular fitted the hard clamshell case perfectly and can even accommodate the binocular with the eyecups kept up for quicker deployment.

The fully folded Leica 8x 20 sitting inside the new case.

The case also allows the Leica binocular to be stored with the eyepieces fully extended upward for quicker deployment.

I was delighted with the new case as it affords far better protection of the optics and is even easier to store away owing to its very small dimensions. The image below shows its size in comparison to the Zeiss Terra case.

Two good clamshells for two fine pocket glasses.

This should serve as an excellent storage case for the Leica pocket glass, protecting it from dust and moisture; an important issue since the instrument is splashproof but not waterproof.

Maybe I should contact Leica Sports Optics with this suggestion?

A Triumph for Aperture & Ergonomics!

Pure sweet!

Both the Leica Trinovid BCA 8 x 20 and the Zeiss Terra ED 8 x 25 are top-notch optical performers. But while the Leica is significantly more expensive than the Zeiss, it is the latter instrument that will prove to be the more versatile. Let’s compare some of the specifications to see why this is the case.

The Zeiss has a larger aperture and bigger exit pupil, making it significantly more effective in low light conditions and for observing the night sky.  The larger exit pupil (3.125mm) also makes it considerably easier to line up your eye pupils rendering the views more immersive and comfortable. The Zeiss has a much larger focus wheel making it the easy choice in cold weather where gloves are worn. In addition, the Zeiss Terra is more pleasant to hold in cold weather since the thermal conduction of its polymer frame is much lower than the aluminium frame of the Leica, which always feels very cold to touch in cold winter conditions.

The Zeiss has better eye relief than the Leica(16mm and 14mm, respectively) making it easier for eye glass wearers to engage with the entire field of view.  What is more, the Zeiss Terra has a considerably larger frame than the Leica pocket glass rendering it much more stable to hold steady during prolonged field use. It also has a noticeably wider field of view than the Leica(6.8 degrees as opposed to 6.3 degrees). And while the build quality is definitely better in the little Leica pocket glass, the Zeiss is really not that far behind it.

I like to think that the ethos behind the design of the Zeiss Terra pocket glass is different to that of the Leica. The frame of the Zeiss is constructed from modern, strong but lightweight materials (fibreglass-reinforced polyamide). Indeed, it only weighs about 75 grams more than the Leica glass. In addition, the Zeiss is fully fogproof and waterproof, whilst the Leica is merely splashproof and so the former has a distinct edge over the latter when moving from cold, damp conditions to a wam, interior environment. One other issue is worth mentioning; the Leica Trinovid BCA is much more fiddly to deploy than the Zeiss. Have you ever tried getting your optimal interpupillary distance with the Leica when attempting to view the night sky in the dark? It can be downright frustrating to say the least! Not so with the Zeiss Terra!

Seen in this light, it’s relatively easy to see why the Zeiss would be my first choice for standard field use. It just ticks so many more boxes than the Leica. Instead of feeling slightly anxious about using a small, ornate pocket glass, that anxiety all but disappears while using the Zeiss. That said, I can see where the Leica might be better suited than the Zeiss. Because the Leica is smaller and has less garish external colours than the Zeiss, it would probably be suited that little bit better to watching sports events from a distance or during an evening at the theatre. Its superior control of glare, internal reflections and less intense diffraction spikes when looking at bright artificial light sources also makes it eminently qualified for observing urban nightscapes and the occasional bout of ‘take anywhere’ tomfoolery.

All of this resonates well with experiences I have had when comparing smaller grab ‘n’ go refractors to my upgraded 130mm Newtonian reflector. Despite being less expensive than the refractors, the larger Newtonian proved the better choice time and time again, showing that you don’t always get what you pay for! Just like the Zeiss Terra, the 130mm Newtonian simply represents more bang for your buck!

Does ED glass in a binocular result in brighter images?

Anyone who has followed my blogs over the years will know that I am sceptical of the claims made by fanatics of ED glass. I found much of their claims somewhat pretentious, including statements like, ” Apos resolve binary stars better than traditional achromats and Newtonian reflectors.” My own tests conducted both in the field and backed up by numerous historical references showed otherwise, which is one of the reasons I got rid of a whole raft of refractors with ED glass and replaced them with much more economical and powerful Newtonian reflectors. It’s relatively easy to find comments about small, low- power ED binoculars where the following claim is  often made, “Binoculars containing ED glass give brighter images than those using traditional traditional crown and flint glass.”

Now, I can certainly see why binocular objectives containing ED glass might focus the visible wavelengths of light they collect that little bit more tightly than those without such elements, which might give them an edge in terms of producing a slightly brighter image, but not so much to make the difference ‘obvious’ or ‘immediately apparent.’ What I did discover is that it is often the quality of coatings applied to the lenses and prisms that result in noticeable differences in image brightness, since more efficient coatings result in a greater light transmission to the eyes. My curiosity was further piqued when I came across this short youtube review, where the presenter noted that a binocular with so-called ‘HD coatings'(read dielectric) produced a much more dramatic effect on image brightness than ED glass-containing instruments with the same specifications utilising non-dielectric(lower reflectivity) coatings.

So I wanted to test the claim that ED glass containing binoculars result in brighter images by conducting a series of observations using three binoculars; my Zeiss Terra ED 8 x 25(containing Schott ED glass and retailing for £270), my Leica Trinovid BCA 8 x 20(bought for £319) and my Celestron Trailseeker 8x 32 binocular(a £126 purchase). The latter instruments have high quality coatings but do not include ED glass containing objectives. The Celestron Trailseeker, in particular, has dielectric coatings applied to the roof prisms, creating the same ‘HD images’ to the Hawke Frontier X 8 x 32 model featured in the youtube clip linked to above. Surprisingly, Leica do not appear to publish details of the coatings they apply to their optical components and no data on its light transmission. The Zeiss Terra ED has a published light transmission of 88 per cent, which you can find on the Zeiss sports optics website.

The stopped down Zeiss Terra ED, effectively working as an 8 x 20 unit.

In order to make the comparison as fair as possible, I made a 20mm aperture stop for the Terra, cutting its effective aperture from 25mm to 20mm but still retaining a magnification of 8x. I then compared the performance of this stopped down binocular to the Leica 8 x 20 (at full aperture) under low light conditions at dusk, when the light was rapidly fading in the evening. I conducted such tests on three separate occasions and, in each case, I elicited the opinions of a number of other individuals, my wife and a few of my students, to ensure that the results were consistent with my own. The target was a tree branch located about 50 yards in the distance. Consensus was reached. The stopped down Terra ED yielded a very slightly brighter image than the Leica 8 x 20.

The stopped down Celestron Trailseeker 8 x 32 working at an effective aperture of 25mm.

But then I set up a similar set of experiments comparing a stopped down Celestron Trailseeker 8 x 32 with an effective aperture of 25mm with the Zeiss Terra ED 8 x 25 at full aperture(so also at 25mm). As with the first experiment, I canvassed the opinions of a couple of my students and my wife on the same target and under late, dusky lighting conditions. The results were very surprising! 3 out of four of us(including yours truly) reported the Celestron to have an edge in brightness over the Zeiss, while a fourth observer reported essentially equal brightnesses in both the stopped down Celestron and the Zeiss at full aperture.

Conclusions: The presence of ED glass did not result in any dramatic increases in brightness in both tests and when compared against the non-ED Celestron, the results seemed to indicate that it had, in fact, a slight edge over the ED containing Zeiss Terra. This further suggested that the Celestron Trailseeker had a light transmission of at least 88 per cent (and possibly a little bit higher), indicating that (as I suspected from other tests) it is indeed a highly efficient light gathering instrument. The results for the Leica Trinovid might also suggest that it may actually have a slightly lower transmission than the Zeiss(88 per cent), although I was unable to verify this in practice owing to the lack of published data on this Leica binocular.

I would warmly encourage other binocular enthusiasts to conduct similar experiments if they have the means. 

These experiments deepen my conviction that the marketing of ED glass in small, low-power binoculars like these, is yet another clever ploy to lure unsuspecting consumers to choose ED-containing binoculars over their non-ED counterparts based on misleading, if not false, claims. Don’t be gulible; never buy a binocular based solely on the presence or absence of low dispersion (ED glass). Check out the other specifications that an instrument offers before parting with your hard earned cash, or try before you buy.

A Vibrant Star Cluster in Coma Berenices

On the Lion’s back; Melotte 111 in Coma Berenices, as seen on page 125 of our guide book.

February has proven to be a very unsettled month weatherwise. The UK has endured not one, but two big storms; Ciara and Denis, causing widespread flooding and general havoc with many communities across the country. But even amidst this grotty weather, the night sky still presents opportunities to observe it, if only for a few minutes at a time. And small binoculars are the ideal instrument to use in these very unsettled conditions, as they require no set up time. If a clear spell presents itself, I’m away out to have a gander.

By mid-February, the constellation of Leo approaches the meridian around local midnight; a sure sign that Spring is on the way. And over in the east, other signs of vernality present themselves, particularly brilliant orange Arcturus, which has cleared the murky horizon and is rising ever higher in the sky, together with the many interesting stars that collectively inhabit the constellation of Bootes. Looking over to the northeast, the bright summer star, Vega, is reassertting itself, while setting in the west, Orion and Taurus are now past their glory days.

This time of year, I like to visit a conspicuous patch of sky just east of the hind legs of the celestial Lion. Easy to pick up in the pocket glass, the famous Coma Cluster( Melotte 111) is no trouble to track down in a dark, moonless sky as a smattering of 4th and 5th magnitude stars concentrated into an area spanning some 5 degrees. Light pollution in towns and cities often drowns out even its brightest members, but from a dark country sky, the Coma Cluster is a fine naked eye sight, with at least half a dozen members being clearly visible to my unaided eyes. But the view greatly grows in majesty when examined with a small binocular. The 8 x 25 Terra frames the cluster very well, where the characteristic ‘V’ shaped stellar configuration makes it child’s play to identify. Several dozen suns are easily discerned in this cluster in a pocket glass and up to 80 members can be pulled out of the dark with larger glasses.

Our guidebook on page 124 informs us that the centre of the cluster is estimated to be about 285 light years away, with its many main sequence stars estimated to have an age of approximately half a billion years. Such a vast amount of time is more than sufficient to prize its stars apart, which goes a long way to explaining why the cluster is so large and sprawling as seen in the pocket glass.  I made a sketch of the Coma Cluster last season using a larger binocular, which is reproduced below for interest.

Insights from an Old Book

Leafing through an old book can reveal  some surprising insights.

My two pocket glasses serve up breathtaking images of the creation. In terms of absolute optical quality, millimetre for millimetre, I would give the edge to the Leica 8 x 20. Yet, in comparing and constrasting it to the Zeiss Terra, I have noted a couple of other ways in which the latter instrument pulls ahead of the smaller glass. The first thing is close focus distance; the Zeiss pocket binocular can focus on objects as close as 1.4m away, while the Leica fares considerable worse in this regard, at about 1.8m. This will likely prove important going forward, as I am fond of observing insects, rock formations, colourful mushrooms and other fungi, as well as flowers at very close range. The Zeiss’ wider field of view will also make those close up views more compelling.

The second thing I have noticed is that, with the exception of strongly illuminated(read sunny) daylight scenes, the Zeiss pocket glass serves up noticeably brighter images. And this is true whether fooling around indoors, glassing out of doors on overcast days and in shaded areas like woods and glades. That the Zeiss was producing brighter images under a wide range of conditions surprised me a little until I happened to pick up an old book from my library, written by the late Leif J. Robinson, former editor of Sky & Telescope Magazine, entitled Outdoor Optics. On page 15 of that text, there is a graph(shown below) of pupil diameter versus age for dark-adapted eyes, as well as how the exit pupil behaves under so-called ‘office illumination.’

Exit pupil size versus age for dark-adapted eyes and under office illunination. Source; Outdoor Optics (1990), by Leif J. Robinson.

The ambient brightness (luminance) is measured in units called Lux, where 1 Lux is 1 lumen per square metre. In this wikilink, it gives the luminance values for various illuminated conditions, including office lighting, which can be anywhere from 300 to 500 Lux. Heavily overcast days can have Lux values as low as 100 though, while observing under the canopy of trees in wooded environments might be expected to be even lower. Looking at the size of the exit pupil under office illumination for my age(51) gives a value of ~3.5mm. Although the particular details of how my own pupil behaves is still unknown to me, these results go some way to explaining why the Zeiss Terra(with an exit pupil of 3.13mm) pulls ahead of the Leica (with a smaller exit puipl of 2.5mm)under these conditions. And gathering more light means that I can discern finer details in many dull or dimly lit scenes of extended objects using the larger 8 x 25 glass.

I intend to investigate this phenomenon further by taking measurements of the luminance under differing lighting conditions and relating this to what my eyes discern using these small pocket glasses. Accordingly, I have ordered up a luminance meter to perform these experiments, and will report back on this matter at a later date.

A New Colour Variant of the Zeiss Terra Pocket Now Available!

Remember how I described the Zeiss Terra 8 x 25 as having rather garish colours that might attract unwanted attention from the members of a crowd at sporting events? Well, I just recently discovered that Zeiss are now offering the Terra in not one, but two colour schemes. As well as the black, blue and grey livery on the original Terra, they now offer it in black, white and blue. And here’s what it looks like:

Zeiss Terra ED Pocket 8x25 Binoculars - Black/Black

Maybe someone from Zeiss was reading my blogs lol?

I think it’s rather handsome; don’t you? Source here.

Hooking up with the Leica Sports Optics Group

I had a few questions about the Leica Trinovid BCA 8 x 20 and decided to contact the sports optics group in the UK with a couple of questions that I was unclear about. The first question I asked them was whether or not the outer lenses of the Trinovid were treated with AquaDura coating. This nanotechnology changes the surface tension of water and oily dirt that happens to form on the glass, causing smaller droplets to coallesce into larger drops, which in turn are much more easily discarded from the lens surface under gravity. It also acts as protective barrier against abrasive forces such as scratching. The reason I enquired about this coating was that the user manual I received did not explicitly state that it had been applied but the online PDF  of the binocular’s technical data did state that AquaDura was indeed applied to the outer lenses. In addition, I asked them to clarify what ‘splashproof’ meant.

Well within 24 hours, I heard back from Leica, who were able to confirm that AquaDura was indeed applied to the outer lenses. They also suggested a way I could test this by breathing heavily on either the ocular or objective lenses to create a temporary fog and watching how this would disappear within seconds. Sure enough, that fog disappeared rapidly. Indeed, I performed the fog test on both the Leica and my Celestron 8 x 32 and was able to verify that the condensed moisture disappeared within seconds on the Leica but lingered far longer on the Celestron ocular lens. To illustrate this, I took a photograph of both ocular lenses just after I fogged them up and again 10 seconds later. You can see that the Leica lens was free of moisture but the Celestron had not yet de-misted.

Performing the fogging test. At the top is the Celestron ocular lens and on the bottom, the Leica ocular lens, just moments after they were fogged up.

The same ocular lenses as seen 10 seconds later. Note that the fog has disappeared from the Leica ocular but is still prevalent on the Celestron.

They were also able to clarify that ‘splashproof’ meant that they would hold up fine in light rain but were not advisable to use in heavy rain or on a boat.

I later contacted Leica UK to tell them about the alternative carry case I acquired to better protect the little Trinovid against the elements. Indeed, I dispatched the same sequence of images I presented earlier in this blog to them. I wasn’t really expecting a reply but within hours I got a very nice e-mail from one of the group members (Tizia). Here is what she had to say:

Leica Camera Onlinestore UK Onlinestore.uk@leica-camera.com
to: Neil English <neilenglish40@googlemail.com>
date: 24 Feb 2020, 16:15
subject: Re: Hardcase for Leica Trinovid BCA 8 x20
mailed-by: leica-camera.com

Hi Neil,

Thanks for sharing! That’s brilliant. What brand is this case? I will make a note of it to let future customers know in case they are looking for a case as well.

Best wishes,
Tizia

[signature_1723328913]

store.leica-camera.com/uk<http://store.leica-camera.com/uk>

I think they liked the idea. And after my teaching this evening, I sent her on the amazon link to the clamshell.

Who knows, maybe Leica might bring out their own version of this nifty little carry case in the near future?

Rise of the Daffodils

The first daffodils grace us with their radiant colour.

On the last day of February, my eldest son and I took off for a walk around the grounds of Culcreuch Castle Estate. Though the weather for most of the month has been downright horrid, no snow has settled in the valley this winter, but it seems to come and go on the hilltops.  During our walk I was delighted to see that the first daffodils had begun to flower. Unlike the south of Britain, where daffodils spring up a few weeks earlier owing to its milder climate, nature seems altogether more pedestrian this far north. Still, the days have lengtened considerably by now, with sunset occurring near 6pm local time. And with longer days, the intensity of sunlight grows noticeably stronger, its rays beginning to bring some warmth to an upturned face, and making observing with the pocket binocular ever more worthwhile.

Nature seems to have been stirred into action in other ways though. I’ve been glassing the  corbies, mostly of the carrion variety, that roost in the conifer trees to the west of the house, where I have observed them carrying nest-building materials; twigs, mosses and the like, in their sturdy beaks in preparation for the arrival of the next generation. Their deep and resonant ‘kaaring’ has become noticeably louder and they seem more anxious than they’ve been earlier in the winter. My neighbours seem to consider them as nothing more than noisy nuisances, but I have always had a soft spot for them.

And there’s also been an unexpected return of one of the Magpies to the Rowan tree in my garden. The original family are still around but on one Sunday afternoon a few weeks back, my wife and I witnessed at first hand some very vicious behaviour within their ranks. One of the group seemed to have been singled out as weaker or less desirable than the others and was attacked by two other Magpies in the group. They forced it to the ground and were pecking and kicking at it, with the obvious intention to injure or even kill it. Were it not for the intervention of my wife, the poor creature might have died. Fast forward a week or so and lo and behold, a solitary Magpie returned in the evening, resting near the centre of the tree which afforded it more protection on all sides by its wiry branches. It looked lonely; almost forlorn.  Alas, I have ventured out to see if it returned on other nights since then, but thus far, there has been no sign of it. I do hope it has survived.

The solitary Magpie hunkering down at the centre of the Rowan tree on the evening of February 24 2020.

Further Experiments on Light

The light meter used to study the relationship between ambient lighting and the brightness of binocular images.

I ordered up a light meter in order to conduct some more experiments on the relationship between light intensity and the perecived brightness of the images served up by the Zeiss Terra and the Leica. It’s easy to use and has been very educational. On bright days, in  a clear, blue sky and in direct sunlight, light intensity can reach 50kiloLux. But as soon as a cloud covers the Sun, the intensity falls to half that level. Dull overcast days (for late February) in the open air yield values of the order of 6-7 kiloLux. Indoors is another matter though. For example, the brightness in my living room under regular illumination falls to just 50 Lux and under these conditions, the larger exit pupil of the Zeiss pocket glass clearly show brighter images. The same is true when viewing objects under brighter indoor lighting levels, such as my kitchen (300 Lux). What is more, observing through a window or from an open door during most any daylight conditions registers values of the order 400 to 500 Lux. My son and I both confirmed that the Zeiss clearly shows a brighter image than the Leica when observing under these conditions, and the readings I have thus far obtained deep inside a forested canopy under the shade of conifer trees show values of about 1.2 and 1.0 kiloLux in strong (overcast) afternoon illumination. Here again, the Zeiss pulls noticeeably ahead in terms of serving up brighter images. My preliminary results with the light meter suggest that at luminance levels less than a few kiloLux, the Zeiss will serve up brighter images under pretty much any conditions.

I am satisfied that these results are real and repeatable and, furthermore, have implications for birders and other nature observers observing wildlife from hides or simple observing stations, where substantial light shade is provided by the structure. Under these conditions, a larger aperture binocular should have a noticeable advantage over smaller instruments, no matter how well made it is.

A Delicate Flower

The Leica Trinovid BCA 8 x 20(right) must be handled with care owing to its small size.

Owing to its diminutive size, the Leica must be handled with considerably more care than the larger Zeiss. No less than four times in as many weeks I have almost dropped the instrument while taking it out of its case! As you can imagine, these incidents were the cause of considerable anxiety on my part and is due to the extremely small size of the folded instrument in my hands. As a result, I have to take extra care removing it and will now only do so at a table or on a couch. Whenever I deploy it, I immediately put the strap round by neck and keep it there until I’m done with it.

That said, I continue to be deeply impressed with the Trinovid’s excellent optical quality. This binocular has truly exceptional control of internal reflections and glare; better than any of my other instruments. Indeed, I have since learned that Leica is a world leader in suppressing unwanted light. After dark on March 1 2020, immediately after a heavy shower of sleet, hail and high winds, the sky cleared briefly in the mid-evening, when a beautiful crescent Moon hung majestically, low in the western sky and just above the tops of the conifer trees where the corbies roost. The Pleiades was located nearby, up and to the right of the crescent, making the apparition a particularly memorable one. I took the opportunity to compare and contrast the images seen through the Zeiss Terra and the Leica Trinovid, noting contrast, stray light levels and image sharpness. Though both instruments served up excellent results with wonderful earthshine on display from its dark hemisphere, the clear winner on this target was the Leica. The bright crescent Moon was more starkly presented in the Leica with almost zero evidence of internal reflections and nary a sign of even the weakest diffraction spike across the field(a common phenomenon in roof prism binos). The Zeiss showed a stronger diffraction spike, made more obvious only by the sheer perfection of the Leica,  and a tad lower contrast in comparison; certainly never enough to induce alarm by my standards, but enough to show that it was nonetheless superior to the Zeiss in this regard.

Contemplating a March Supermoon

A bright full Moon rising in the east at 6.17pm on the evening of March 8 2020.

The full Moon of March 8 2020 rose early in the evening, and as blue sky gave way to twilight, proper darkness finally set in after 7pm local time. I ventured out with my 8 x 25 pocket glass to observe its steely grey countenance. On this evening, where clear spells were interspersed with frequent heavy wintry showers, the brilliant Moon looked stunning in the little pocket binocular, navigating its way through patchy clouds and creating spectacular light shows as it did.

Presenting itself a little bigger and brighter than normal, this so-called Supermoon arises from its slightly elliptical orbit, which, every now and then, carries it closer to our planet than normal. With such a big, bright orb as this, it’s easy for the imagination to run amok. Tonight I saw it as one enormous canvass of sorts, or maybe some gigantic work of plaster of Paris adorned with God’s footprints!

As I relaxed to take in the naked eye view for a few moments, I noted that not so far away from big, bright Luna, there appeared a few faint stars, perhaps of the third magnitude, winking in and out of view as the rainclouds marched their way eastward across the sky. Now the Moon, I thought, is usally about magnitude -12.7 and with its closer approach it might well have reached -13 or thereabouts. So, my average eyes could make out stars that were about 16 magnitudes fainter than the Supermoon. A little math shows that the brightness differential between these faint naked eye stars and the Moon is of the order of 2.5^16 which is ~2,300,000.

Wow! What an amazing dynamic range the human eye possesses!

Recalling some technical details from my amateur photography days, that amounts to about 21 photographic stops! Then I found out that the dynamic range of the best digital cameras was only about 15 stops or so!

And did you know that the human eye can detect a single photon of visible light with an energy of the order of 10^-19 Joules. That’s 10 bilion billionths of a Joule!

“We may be small and insignificant in the scheme of things,” I thought, as I continued to admire a few minutes of a bright Moonlit sky, but, nevertheless, our Creator packed us full of technological wonders!

Great are the works of the Lord;
    they are pondered by all who delight in them.

Psalm 111:2

Drawn to the Light of the Great Outdoors

The River Endrick walk, Fintry.

With the days lengthening rapidly in March, the quality of light upon the landscape continues to improve, making glassing with the pocket binocular more productive and worthwhile. The strengthening sunlight illumines the hills, the fields, the trees, the rivers and streams, making anything with colour stand out with greater urgency. The trees are well on their way to shooting new leaves and the thorny gorse bushes have already begun to flower in their radiant yellow hues. With the improving strength and quality of sunlight, the performance of good quality pocket glasses become ever more apparent, allowing one to image targets in the field with breathtaking clarity. And what a beautiful world our Lord created for us, with its mindboggling complexity that just cries out to be explored by the naked eye and with quality tools that greatly extend our vision.

Beautiful, delicate gorse flowers.

Fear of the COVID-19 virus pandemic seems to be spreading faster than the virus itself. But I refuse to be inhibited by it. The human body is well designed to cope with viral infections but there are ways to boost the immune system by simple lifestyle changes. Walking in the great outdoors provides the necessary exercise to keep your cardiovascular system in tip-top condition. The virus can only survive a few hours in the open air, making it very unlikely to cause infection in this environment, especially if you keep away from crowds.

Gazing up into a great, old conifer tree with a bright blue-sky background can induce deep feelings of joy.

Sunlight too helps de-activate this pathogen by denaturing its protein coat,  as well as having a proven ability to stumulate the human immune system. Drinking plenty of pure, fresh water and including a wide variety of nutritious fruits and vegetables in your regular diet also helps your body fight infection. Some dietary supplements, including sulphur-rich garlic and N-Acetyl Cysteine(NAC) will also help your body cope better should you become infected. Temperance in alcohol consumption is always advisable too. Having said all that, few people appreciate the power of prayer to positively impact the immune system. Pray for strength, for endurance and for wisdom. As the Psalmist declared long ago:

Whoever dwells in the shelter of the Most High
    will rest in the shadow of the Almighty.

I will say of the Lord, “He is my refuge and my fortress,
    my God, in whom I trust.”

Surely he will save you
from the fowler’s snare
and from the deadly pestilence.
He will cover you with his feathers,
and under his wings you will find refuge;
his faithfulness will be your shield and rampart.
You will not fear the terror of night,
nor the arrow that flies by day,
nor the pestilence that stalks in the darkness,
nor the plague that destroys at midday.
A thousand may fall at your side,
ten thousand at your right hand,
but it will not come near you.

                                                     Psalm 91:1-7

Bidding Farewell to Old Friends

The evening of March 15 2020 proved to be cool, calm and mostly clear, so wrapping up warm after supper, I ventured out with my trusty 8 x 25 pocket glass, when I was immediately greeted by a sky full of stars! Brilliant Venus shone in the west with an intensity I had not encountered in many years. Like some great lighthouse in the heavens, it was bright enough to cast shadows of some of the more delicate tree branches on my backgarden lawn! Needless to say that the apparition was quite surreal!

By now, mighty Orion had past the meridian and was sinking towards the western horizon. But I was glad to see that big, orange Betelgeuse, which had spent a few months diminishing in brightness had, by now, regained much of its former glory. The little binocular beautifully framed the pure white stars of the Hunter’s belt, as well as showing up many fainter members of Collinder 70. And lower down, the Great Nebula in the Swordhandle was still presenting its visual magic with wonderful clarity. Ahead of Orion and even lower down in the western sky lay Taurus, with the refulgent stars of the Pleiades and Hyades still presenting well in the pocket glass. High above them I saw Auriga the Charioteer, also remaining well placed to glass its trio of ghostly Messier open clusters – M37, M38 and M36 – arranged nearly in a line from east to west, respectively, and almost fitting in the same binocular field. You can find them for yourself by taking a look at the star chart on page 89 of our guide book.

By this time of year, brilliant Perseus and Cassiopeia had wheeled their way far off to the north. But I was still able to get a reasonable view of the Double Cluster, though it couldn’t hold a candle to its glory days during the height of winter, when it was much higher in the sky. The exceedingly rich constellation of Gemini lay on the meridian, with myriad faint Milky Way stars coursing through its confines, and followed fast on its heels by the large and domineering Leo. It was clear to me that the sky was announcing the imminent arrival of spring!

Although glassing the night sky with a small binocular always upwells deep feelings of joy, I felt somewhat melancholic on this occasion, as I knew that the brilliant stars of winter would gradually be lost in the strengthening twilight that attends the unstoppable march of the seasons. But as the old adage proclaims, “abscence makes the heart grow fonder.”

I will see them again next season, God willing.

Oot ‘n’ Aboot

The coronavirus pandemic has gripped the nations with fear. But unlike COVID-19, the fear virus is far more contagious. It fills the godless with dread, bringing their mortality and materialism into sharp focus. And while anyone can catch the coronavirus, most Bible-believing Christians across the globe are entirely immune to the fear virus. You see, we’re sealed by the Holy Spirit(the third person of the Trinity) and so do not let such issues worry or control us.

The boys are off school but their education must continue; indeed, the same is true for many of their peers, and so my days are now occupied offering free online tuition to many of my former students to keep them focused. Truth be told, I’ve never been busier!  I still  take time to enjoy the beauty of God’s created order, whether it be the rural landscape around me or the strarry heaven above. Heeding the guidelines issued by the government, our movements are more restricted than in normal life, but thankfully we can still go for walks once a day. And there’s always the back garden to enjoy.

The daffodil-lined walk along the Lade, Fintry.

On the afternoon of Friday, March 27, my eldest son and I decided to go on a different amble from the route we normally take. Called the Lade, after the old mill lade that once stood on the site, it runs parallel to the Endrick River, and provides many opportunities for glassing. As we walked along the narrow, muddy path, under woody glades, I remembered the many occasions I used to take my boys along its winding track, when they were much younger and much more naieve. We chuckled amongst ourselves as I  pointed out the old disused barn where ‘Wee Willy Winky’ lived, or the scary looking tree trunk shaped like a monster. The barn remains but the ‘monster’ tree trunk had all but been reclaimed by nature.  My son carried his 8 x 32 and I brought along my versatile 8 x 25. Even in heavily overcast skies, the light is now good and strong making a pocket binocular a great choice to bring along to enhance the naked eye experience.

Because the trees have not yet produced their leaves, the Lade offers many opportunities to look out across the Endrick Valley to the Campsie Fells beyond.

The Lade walk eventually brings us to Craigton Pond, providing a natural fresh-water habitat for wading birds and a good spot to spend an afternoon fishing for Roach, Perch, Carp and other bony fish during spring and late autumn. In summer, the entire pond becomes choked up with water lillies which renders fishing all but impossible. We found the pond to be a hive of activity for various species of duck, and being a novice birder, I always delight in being able to identify new varieties with my pocket glass. On this afternoon, I was able to positively identify the female Goosander(mergus mergander), with its fetching grey plumage covering much of her body, white neck, chocolate-brown crown and nape, and a very long and slender hook-tipped sawbill in striking vermillion. When I first glassed the bird, I was sure it wasn’t a duck, but as soon as we got home, my good old RSPB guidebook informed me otherwise.

A good birding and fishing spot; Craigton Pond, Fintry.

Nature is such a treasure to be revered certainly; an endless wellspring of divine revelation, but it is not be worshipped like the New Agers and Extinction Rebellion fraternity seem to do. I suppose this modern nature worship got a big boost from the influential writings of the Dutch philosopher, Baruch Spinoza(1632-77), who conceived the Godhead as the entire material cosmos with its physical laws comprising the Divine essence. But though a Jew, Spinoza was barely a Jew at all. He completely rejected the Judeo-Christian concept of God as existing eternally beyond nature. Had he spent more time studying the printed words of the Torah – rather than the white spaces surrounding them,  Spinoza might well have formed an alternate opinion. In fact, the gods of all the eastern religions hold to something similar to Spinoza’s pantheism. To the Biblical God, pantheism is a fabrication; an idea of purely human construction; just another idol, if you will.

An Encounter with a Crescent Moon & Venus

Around 8pm on the evening of Saturday March 28 2020, on the eve of the return of British Summer Time(BST), I ventured outside to examine the progress of a clearing sky, and though some large cloud banks were still present, I spied a beautiful crescent Moon and a brilliant planet Venus less than seven degrees apart,  low down in the western sky.  How did I come on seven degrees you might legitimately ask? I was just able to image both objects in the same portal served up by my Zeiss Terra pocket glass, which offers up a true field of 6.8 angular degrees. The crescent Moon in March is one of the best times of the year to witness earthshine, where the lunar darkside is easily made out and breathtaking to behold in the pocket glass. I was struck by its haunting serenity, faithfully beaming its silvery rays upon us; a reminder that nature in all its grandeur dances to a different drum to anything in the human world; a temporary panacea from the trouble of our times.

A Gorgeous Sunset & Splendid Binocular Vignette

Sunset, Isle of Lewis, March 30 2020. Image credit: Gavin Porter.

Amid all the chaos wreaked by the COVID-19 pandemic, there are splendid moments of calm.

The evening of Monday March 30 2020 proved to be especially lovely in this regard. There was a gorgeous sunset this evening, with nary a trace of wind. It was more ruddy than usual owing to a greater amount of dust in the air from the prolonged dry spell we are currently experiencing in Scotland. An acquaintance of mine, Gavin, based on the picturesque Isle of Lewis in the Outer Hebrides, captured a beautiful sunset(see above) and kindly shared it with me. Coincidentally, I was also outside enjoying the same sunset but was even more captivated by the sight of a late crescent Moon and Venus(below) shining brightly in a clear, tranquil sky.

A bright crescent Moon and Venus (lower right). 8.46pm Monday March 30 2020.

On such an occasion I thought it fitting to bring out my little Leica Trinovid BCA 8 x 20, which produces especially beautiful images of the Moon, owing to its razor sharp optics and superlative suppression of glare. I was not disappointed! While it did show the Moon in all its glory with its prominent earthshine, I was even more thrilled to discover that the planet Venus was enjoying a close encounter with the Pleiades. Indeed, the Leica pocket glass captured both objects easily within the same field of view. I made a little sketch in my notebook to commemorate the apparition.

The Pleiades & Venus as captured by the Leica Trinovid 8 x 20 pocket glass.

The tiny, precision pocket glass that is the Leica Trinovid would make an excellent optical tool for keen photographers and portrait painters alike, as it produces exquisitely fine vignettes of the Creation. What it lacks in sheer aperture, it more than makes up for in the stunning clarity of its state-of-the-art optics.

A little bundle of joy: the Leica Trinovid BCA 8 x 20.

Tonight’s apparition in the western sky can be enjoyed by anyone, whether they live in the city or the country. So if you’ve got a clear sky, why not go out and have a look. It is sure to lift your spirits!

Showing the fruits of the Spirit during Lockdown

Bright April days trigger plants to shoot green leaves and flowers.

April is a month when the Creation goes into over-drive, especially if the Sun comes out to play, and, in this capacity, we have been blessed with a good run of fair and warm weather. Suddenly, the buds on the trees mature and young leaves appear. Early spring flowers burst into bloom, the grass is growing in the fields and the newly arrived lambs in the farmsteads ’round the estate are thriving. But there are always dangers posed to these young creatures. On one afternoon, I glassed a curious adult buzzard that had landed in  just a few yards away from a resting lamb, hoping that its mother would make a mistake and move too far away. Luckily, the buzzard got spooked and flew off, perching in a strong branch of an old oak tree, where it kept a keen eye on its potential prey. Losing a few lambs to raptors each year is the rule rather than the exception ’round these parts. I suppose all of God’s creatures need to eat.

While we are still in the grip of this viral pandemic, there are still many things to put a spring in our steps. When I see so many individuals confined to apartments around the world, especially in big towns and cities, with no gardens to roam in, I count my lucky stars that I have such a space to make the most of the lockdown. And there’s always plenty to see and do; the vegetables have been planted, a new fence has been laid, and another one painted. The trees around its border have been trimmed to let in as much light in the evenings. My neighbours are busy doing up their own gardens, and though we still have to practice social distancing to curb the spread of the pathogen, we nonetheless enjoy some lively banter across fences.

The great reduction in human nocturnal activity has paid unexpected dividends for stargazing too. ‘Glasglow’ is now much less conspicuous looking southward after dark, and moonless nights become even more spectacular to explore with a pocket binocular. Venus and the Pleiades have almost locked horns now for some days, but as we approach the Easter weekend, they are slowly inching apart.

Because of their close proximity, the corbies that roost in the conifer trees to the west of the house are fascinating to watch with my little 8 x 20 and 8 x 25 glasses. Though they make an awful racket flying to and fro from their nests, I enjoy watching their antics as their chicks hatch.

Much to my surprise- remember I’m not much of a birder – my pocket glass focused in on some high-flying birds in the sky above the house on the afternoon of  Maundy Thursday, April 9. Though it can prove difficult to identify species at distances of a few hundred yards, I was amazed to discover that they were most likely swallows that had returned from southerly climes to spend the summer in Britain. The pocket glass allowed me to see their forked tail and a lucky glimpse of one such bird that came closer than the rest revealed its black and white plumage. But what really gave them away was their very distinctive high-pitched ‘tswit,’ which fired off a very old memory trace in my mind hearkening back to my youth.

Unfortunately, there will be no worship in our local church this Easter Day because of the government-imposed shutdowns, but we can still link up via social media like Zoom, Facetime etc. And while our civic freedoms are still greatly restricted, we still have great freedom in Christ, who continues to shower us with the wholesome fruits of a believing heart:

But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness,  gentleness and self-control. Against such things there is no law.

Galatians 5:22-23

Things to be Grateful For

I find it ironic in the extreme that ever since the lock down began some five weeks back, the weather here in central Scotland has been very pleasant, with long sunny days, hardly a drop of rain and clear skies almost every night. Indeed, I can’t remember the last time we’ve enjoyed such a long run of fair weather. The Creator remains gracious even in these troubling times!

Indeed, I have managed to observe my tally of spring double stars and deep sky objects much earlier in the season than usual and all my Newtonian reflecting telescopes have been employed to the full. The trees are now covered in fresh young leaves that are a delight to glass with my pocket binoculars. The evening sky just after sunset in these last days of April 2020 have been particularly awe-inspiring with Venus now at its brightest and a crescent Moon nearby in the western sky. On the evenings of April 25 and April 26, I took a few photos of the apparition with my iphone. And while Venus and the Moon were much too far apart to capture in my Zeiss Terra pocket with its 6.8 degree field, on the evening of April 25 they were just close enough to sight in the same field of view at ’round about the same time(see below) on the following evening( April 26).

The crescent Moon and Venus(at top) right as it appeared after sunset on the evening of April 25 2020.

The Venus & Crescent Moon apparition as it appeared on the evening of April 26 2020.

Such lunar and planetary conjunctions are rare but they certainly help raise the spirits in these troubling times.

When proper darkness falls on the landscape, I’ve been visiting a few optical double stars around the night sky that are well seen in the pocket binocular, and I intend to present a list of such objects in a later episode of this blog. So stay tuned!

The Terra Pocket Now Moved to China?

The original Zeiss Terra pocket glasses were made in Japan (Katsuma Optical) under Zeiss supervision.

I recently received a message from a chap named Olly, in which he stated that his newly acquired Zeiss Terra pocket glass now had ‘China’ printed both on the binocular and on the box it came with. From their launch several years back, I understood that these pocket glasses were the exception to the rest of the Terra line, where all of the larger models were being manufactured in China. I asked him if he would send me on a photo of his new binos showing the Chinese origin, but he didn’t respond. Thus, I contacted Zeiss sports optics directly to find out if in fact it was true. Alas I have yet to receive a reply! My next line of investigation took me to two UK suppliers of these pocket binoculars and thankfully, they were quick to reply. I can confirm that Olly’s news is true; the Zeiss Terra pocket glasses, like the larger Terrra models, are now manufactured in China, but still carry that valuable Zeiss design. I also note that the retail price for these units remains unchanged.

What will the change of country of manufacture do to these superlative little pocket glasses? Realistically, probably nothing, save perhaps for slightly inferior quality control. Would I personally be worried about that? Honestly, no! I have several binos that offer excellent performance and all are assembled in China, so I’m guessing that the consumer will not notice the slightest bit of difference between the Japan-made model and its newer Chinese made counterpart. Of course, I would love to hear from anyone who has experienced anything out of the ordinary with respect to these newer Terra pockets, or if they have had a chance to test the older and newer models in a side-by-side comparison.

For journalistic purposes, I’ve made a note of this change in a new postscriptum on my original review of the Zeiss Terra ED 8 x 25, which you can see here.

Cicely’s Way

Cicely’s Way, Fintry.

May has arrived at last, and the idyllic weather continues apace. The landscape is bathed in life-giving sunshine, and the wildlife is thriving. A couple of days of rain has soaked the ground, helping to keep the gardens looking vibrant and there is plenty of fresh green grass for the lambs and calves coming into the world. Conditions are also perfect for taking a pocket binocular along for a good walk. As I’ve touched on earlier, Fintry is blessed by having a number of great walks and the most recent one created is Cicely’s Way, named in honour of an elderly lady in our village, who has dedicated much of her free time over the years to planting flowers on the main road of our village and decorating the window ledges of our village hall, keeping it looking beautiful. Indeed, Fintry has won many prizes over the years for its outstanding natural beauty and on one occasion it even won first place the prestigious Britain in Bloom award.

Cicely’s Way has extensive hedgerows, which is great for glassing small birds that frequent the branches; robins, finches, chaffinches and even the odd song thrush hunting for worms and insects.

The river walkway has now become crowded with bunny rabbits which are excellent binocular targets. But what I most enjoy is the vibrant colours of young, tender leaves that have a beautiful translucent quality during Spring. In the evenings, as the Sun loses altitude, it shines its golden rays right through them and I enjoy glassing their intricate structures as they thrive in the warm weather. Slowly they will become darker in tone and that magic light green hue will disappear as they mature and darken as summer arrives.

With the days growing ever longer, the nights become progressively shorter and soon the summer twilight will succeed in banishing true darkness for a season. But what is lost in night time observing is more than made up for in daytime glassing activities. This year, we have booked a lovely cottage on the outside of Gairloch, a small picturesque village way up in the northwest Scottish Highlands on the shores of Loch Gairloch, Wester Ross. Hopefully, we will get to enjoy that holiday which will occur in early July, when the days will be very long and I can glass to my heart’s content!

The village of Gairloch, Scottish Northwest Highlands. Image credit: Wikipedia.

The new origin of the Zeiss Terra pocket glasses is now being debated. Zeiss did finally get back to me, stating that these binoculars are still being manufactured in Japan, although a number of individuals have now come forward claiming that they are now being made in China – and with photographic evidence to boot. Such a question doesn’t really bother me but I guess it’s important to establish the truth in any matter. Time will tell!

At home in the great outdoors.

That having been said, I am using the little 8 x 25  Terra more than ever. Its super light weight, good ergonomic design and excellent weatherproof optics makes me reach for it time and time again.  And I look forward to bringing it to other wild places once the COVID-19 lockdown measures have been relaxed.

Cruising the Early Summer Milky Way

The extraordinarily rich constellation of Cygnus reaches a decent height above the eastern horizon in the wee small hours of mid-May. See page 137 of our guide book.

From mid-May onwards into the summer, the nights grow painfully short, making astronomy more and more challenging as the solstice approaches. But that being said, in the wee small hours after midnight, the majestic constellation of Cygnus reaches a good height over the eastern hills across the Endrick Valley from our home. And even with a low lying waning Gibbous Moon in the sky, that part of the sky remains quite dark, making it worthwhile to scan with a small pocket glass. Although I have by now completed nearly all my telescopic deep sky observing until the return of dark skies again in August, and while Cygnus is much better positioned in the later months of the year, it is still a joyous experience to explore the rich bounty of Milky Way stars coursing through this great northern constellation.

Brilliant white Deneb, creamy white Sadr and the lovely orange Albireo trace out a  great line through which the pocket glass can soak up hundreds of fainter stars. Moving the glass between Deneb and Delta Cygni, the little Zeiss 8 x 25 does a sterling job of resolving the much celebrated o^1 Cygni, with its beautiful colour contrast pairing of stars; orange & turquoise. Even with such a small instrument, it is possible to gain a sense of the immensity of the stellar Universe beyond our solar system with many of the stars visible in the generous 6.8 degree field being located hundreds or even thousands of light years away.

So numerous are the stars, so magnificently they shine through the darkness

Faithful comforters, fountains of radiant beauty,

How great is our God who fashioned them all with His hands!

And though uncountable by mortal human minds, each one is intimately known to Him who gives them light and life.

The Psalmist of old declares it:

He counts the number of the stars;
He calls them all by name.
Great is our Lord, and mighty in power;
His understanding is infinite.

Psalm 147:4-5

Long Range Microscope

A flowering Rhododendron.

With daylight now being strong and long-lived, the pocket binocular comes into its own as a long-range microscope, allowing one to study close-up views of the creation in extraordinary detail. And though I am possession of two fine pocket glasses, it is the larger Zeiss Terra 8 x 25 that is now pulling well ahead in terms of frequency of use. Because it is larger and easier to use than the Leica Trinovid, and owing to its rugged, fully waterproof casing, it’s simply the best choice in most situations. This is particularly the case when close-up views of nature are required. The Zeiss has a much shorter close focus and wider field of view than the Trinovid, making observations of rocks, insects, flowers, tree bark and leaves that little bit more engaging.

Close-up glassing of nature is not for everyone however. This is because zooming in at something at such close range( two metres and under) can be a bit discombobulating for some observers who struggle to get their eyes comfortably placed behind the eyepieces. What happens here is that your eye pupils have to move together more in order to properly image the target, but the situation is considerably improved by pushing the barrels of the binocular closer together to reduce the IPD. I discovered this trick quite quickly and naturally in the field, and it works well for many roof prism binoculars. Of course, there are other types of binocular that are even better suited to close up viewing of nature, particularly the economically-priced reverse porro prism models being offered by a number of optical firms. But what you gain in close focus with these binoculars, you lose in portability, especially pocket portability.

Solar Peculiarities

A babbling brook bathed in warm sunshine; Culcreuch Castle Estate.

God continues to bless our weather during the continued lock-down here in Scotland. The brilliant Sun at the centre of our solar system provides the light and warmth that makes succulent strawberries grow in our greenhouse and fresh rocket for our salads. The apple blossoms are ablaze with colour  and the mild winter we have come out of will ensure an abundant harvest in the autumn.

How much we take for granted the life-giving rays of the Sun! Indeed, as astrophysical science progresses, we are learning that it’s not only the most stable star yet identified in the starry heaven, it is also peculiarly quiescent compared with other sun-like stars in the solar neighbourhood. Indeed a recent survey of 369 sun-like stars showed that their activity is considerably higher(about five fold on average) than our own Sun, which is quite unexpected given what we currently understand about stellar astrophysics. If this is generally true then it might spell more bad news for those who continue to hold out for finding another habitable planet out there in deep space. Indeed, our Sun varies its luminosity by only 0.07 per cent in any one twenty four hour period!

For over a year now, I’ve been monitoring the Sun with a few of my binoculars, but most especially my trusty Pentax PCF 20 x 60, which produces a decent image scale to monitor sunspot activity, but I have also constructed neat little white-light solar filters for my 8 x 25 pocket glass, which I also find fun to use on occasion. And though I certainly have not monitored the Sun every day because of other commitments, my log books show that it has been over a year since I recorded my last sunspot on the solar photosphere. But recent professional studies show that the Sun in 2019, and thus far in 2020, has shown no sunspots, however small, for most of this time, which has prompted some astronomers to think that it may be entering an unusually deep minimum and could even be commencing a lockdown of its own. If that’s the case, past history suggests it may not bode well for planet Earth, since prolonged periods of solar inactivity has been linked to higher cosmic ray fluxes in Earth’s upper atmosphere which triggers more electrical storms, as well as significant global cooling. Maybe this is another sign in the heavens, just like mighty Betelgeuse exhibited just a few short months ago? Let us pray that the Sun will soon be roused from its unusually long slumber!

Exploring the Twilight

Strong twilight as captured at 11 pm local time on the evening of May 24 2020.

As May comes to an end, so too does the summer twilight grow ever longer. I like to take the time to venture out after sunset and watch the first appearing of the stars, as our great solar furnace makes its way further below the northwestern horizon. Twilight can be a magical time for quiet contemplation and prayer. The noisy Corbies settle down to sleep, and the gentle evening winds peter out, leaving only the faint, babbling sound of the nearby river to fill the air.

Brilliant Vega is invariably the first to appear to the naked eye high up in the east, while yellow-orange Arcturus can be spotted just a few minutes later, rapidly approaching the meridian. Low in the north the lovely yellow light of Capella can be made out and waiting a little while longer, the soft white light of Deneb over in Cygnus peeps out to say hello. By then the sky has become sufficiently dark to reveal the magnificent asterism of the Ploughshare dominating the zenith.

During these times, I can enjoy prolonged periods with the pocket glass, capturing picturesque scenes of faint starlight winking into view over the silhouetted branches of trees. More often than not, those same scenes are temporarily interrupted by the appearance of hunting bats, frantically flitting through the field of view, as they hone in on their insect prey. Many a late evening during June and July can be enjoyed in much the same way. Still, no two twilit nights are ever quite the same. This evening, for example, I was lucky enough to spy a beautiful, slender lunar crescent very close to the northwest horizon and almost hidden by a thin veil of wispy cloud at 10.15 pm. And if that were not exciting enough, I was also most fortunate to witness a bright fireball rushing across the sky overhead, moving roughly from north to south at five minutes to 11. Indeed, it was probably one the brightest fireballs I have ever witnessed in such strong twilight!

Such are the surprises that attend an evening out with a pocket glass. And who knows how another day in May will end?

 

To be Continued………………………….

 

 

De Fideli.

Bible Review: Tree of Life Version(TLV) Thinline Edition.

The ornate cover of the TLV Thinline edition.

Then I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and supplication, when they will look toward Me whom they pierced. They will mourn for him as one mourns for an only son and grieve bitterly for him, as one grieves for a firstborn.  In that day there will be a great mourning in Jerusalem, mourning like Hadad-rimmon in the valley of Megiddo. 

Zechariah 12:10-11

 

Title: Holy Scriptures: Tree of Life Version

Publisher: Baker Books

ISBN: 978-0-8010-1921-0

1216 pages

Single satin ribbon marker

Gold gilded page edges

Price: £16.10 (UK)

 

The Bible is God’s love letter to humanity. Some 40 authors, writing independently of each other over centuries and millennia, under divine inspiration, composed its 66 books that form a highly coherent narrative which speaks of God’s desire to tabernacle with humanity, to live among us and guide our thoughts and actions. It has the power to transform lives for the supreme good and, until fairly recently, its moral teachings formed the cornerstone of western civilisation.

Today, we are blessed to have many excellent translations of Holy Scripture to suit most everyone’s needs, and as an avid student of the Bible, I count it as a great blessing and source of comfort to be able to read the words of our Creator in the various thought-for-thought and word-for-word translations now available. That said, some versions of the Bible are more interesting than others. And this new Tree of Life Version(TLV) is of particular note. What makes it stand out from the crowd is its introduction of key Hebrew words that emphasise the authentic Jewish origin of the Biblical narrative.

First published in 2011, the TLV was the brain child of Daniah Greenberg, a gentile lady who betrothed a messianic Jew ( who also accept Jesus as their Messiah), and who came to recognise the need for a good Bible translation that re-introduced some Hebrew words into Scripture, so as to remind Christians that we share a rich tradition with the Jewish community; after all, there is no denying that their God is our God too! Greenberg, who now serves as President of the Messianic Jewish Bible Society, commissioned a small team of 32 Jewish Bible scholars to produce a brand-new translation of the Holy Scriptures. This review will take a close look at the Thinline version of the TLV, a smaller, more portable rendition of the larger giant print edition, which I commented on in an earlier blog.

One would think that the task would merely involve taking an existing Bible version and replace some key words with their Hebrew equivalent. But Greenberg had an altogether more ambitious goal: to get the scholars to re-structure the sentences from the traditional Greek format and rewrite them in the distinctive cadence of the Hebrew language. And it is this achievement that renders the TLV so distinctive and powerful.

Most modern English Bibles have greatly diluted the Jewish accent of the original Scriptures. But the fact remains that Jesus was a Jew; his name is not Jesus but Yeshua. His mother was Miriam and not Mary. Jesus’ half brothers were Judah and Jacob, not Jude and James. Indeed, many of the modern English translations have all but purged much of the original Hebrew context of the Scriptures which has no doubt contributed to replacement theology or supersessionism – the erroneous notion that the Church has replaced Israel. Yet, a careful study of the entire Bible clearly reveals that God has not at all finished with Israel. On the contrary, the final events in human history will make Israel and the City of the Great King – Jerusalem – of central importance at the closing of the age.

That’s why I feel it’s important for Bible believing Christians to try to re-connect with some of the original Hebrew terminology, or at least their English transliterations. And that’s where the TLV really shines. God the Father is referred to as Adonai or Elohim. The Holy Spirit is Ruach ha-Kodesh. The sabbath is Shabbat and the saints, Kedoshim. These re-introduced terms greatly enrich the Biblical narrative and present an altogether refreshing change from the norm that I believe many avid ‘Bibliophiles’ will appreciate.

The TLV also departs from the traditional way in which the individual books of the Bible are presented, adopting instead the traditional Jewish rubric. The Torah(Law) is presented first, just like a regular Bible – covering the five books attributed to Moses;  Genesis, Exodus, Leviticus, Numbers and Deuteronomy. This is followed by the Neviim(Prophets); from Joshua right through to Malachi. After these the TLV presents the Ketuvim(The Writings) featuring the Psalms, Proverbs, Job, Song of Songs, Ruth, Lamentations, Ecclesiastes, Esther, Daniel, Ezra, Nehemiah, 1 & 2 Kings, and 1 & 2 Chronicles. So it’s the Christian Old Testament, but with books presented in a different order to its conventional modern equivalent. The New Testament order of books is however identical to any regular Bible. In ‘shuffling’ the Biblical deck, as it were, the TLV offers readers a new and exciting way to study and assimilate the word of God, to both strengthen and deepen your faith.

To my mind, the TLV steers a middle of the road path between translations that are highly literal( so-called word-for-word) and those that follow the principle of dynamic equivalence (thought-for-thought) but is also respectful of other highly thought of translations such as the King James Version. For example, the TLV maintains classic phrases lost to many modern translations such as Behold and Selah (which is thought to represent an interlude or pause for thought) found in the Psalms. Another change the reader will notice is the absence of the word baptism, which implies infant baptism, which was most likely not practised by the earliest followers of Yeshua and indeed only appears as a controversial topic in the third century AD  (see Tertullian’s c 206 AD, de baptismo, ch. xviii). The TLV re-introduces the proper terminology here; Immersion. Thus John the Baptist becomes John the Immerser, etc. This is a more accurate description of how the earliest believers – all of whom had come of age – symbolically affirmed their dedication to the Christian faith and so feels more natural and less contrived than sprinkling luke warm water on the head of an infant who is not cognisant of the significance of the event.

Unlike many popular, thought-for-thought translations, such as the NIV and NLT, the TLV maintains a very conservative line on keeping accuracy a priority. For example, consider Romans 1:16 in the NIV, which dispenses with the word ‘Greek,’ replacing it with ‘Gentile’:

For I am not ashamed of the gospel, because it is the power of God that brings salvation to everyone who believes: first to the Jew, then to the Gentile.

Romans 1:16(NIV)

The TLV maintains greater accuracy like the more literal, word-for-word translations available(e.g. the KJV, NKJV, NASB & ESV):

For I am not ashamed of the Good News, for it is the power of God for salvation to everyone who trusts—to the Jew first and also to the Greek.

Romans 1:16 (TLV)

The reader can thus be assured that such close attention to linguistic details is strongly adhered to throughout the TLV, ensuring that the Bible reader is getting a highly accurate rendering of the Holy Scriptures.

Notable Features of the Thinline Edition of the TLV

The soft faux leather covering and Smyth-sewn binding makes the TLV open flat on the table.

The thinline TLV measures 5.5 inches wide, 8.5 inches long and just 1 inch thick. The font is clear, approximately 9-point sized, and is line matched to minimise ghosting.

The thinline TLV has a beautifully designed spine:

The decorative spine of the thinline TLV Bible.

 

The TLV text doesn’t have an overwhelming number of Hebrew words, so you’ll rapidly learn those words and phrases. But just in case you get bogged down, there is a nice little glossary at the back where you can quickly look up the meaning of any word that you’re unfamiliar with.

The TLV has a small glossary at the back which you can consult if you’ve forgotten the meaning of any Hebrew phrase you come across.

Like the Giant Print edition, the Thinline TLV also contains a number of Hebrew prayers and blessings, the Lords Prayer and the Aaronic Benediction. These can all be found after the Scriptures are presented. This is a wonderful Bible for devotional study at home or to take along to church with you.

The beautiful gold gilding on the page edges of the TLV.

 

Well, I hope you will understand why the TLV has become one of my favourite Bible translations for both accuracy and poetic beauty. These are difficult times to be sure but they are also exciting because we can see world events aligning just like the prophets of old and Yeshua, whose testimony is the very spirit of prophecy (Revelation 19:10) foretold.

Neil English is working on a brand new book on Newtonian reflectors. If you like his work and wish to support him in your own small way, why not consider buying one of his books? Thank you and God bless you!

 

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.