Invictus

Tiberius; the Measurer.

Tiberius; the Measurer.

 

 

 

 

 

 

 

 

 

A Work Dedicated to the Faithless Generation

 

If men could learn from history, what lessons it might teach us! But passion and party blind our eyes, and the light which experience gives us is a lantern on the stern which shines only on the waves behind.
                                                                    Samuel Taylor Coleridge (1772-1834)

The first glance at History convinces us that the actions of men proceed from their needs, their passions, their characters and talents; and impresses us with the belief that such needs, passions and interests are the sole spring of actions.

                                                                    Georg Hegel (1770-1831)

                                                       Who loves, raves.

                                                                                        Lord Byron (1788-1824)

 

Culture: some definitions
The quality in a person or society that arises from a concern for what is regarded as excellent in arts, letters, manners, scholarly pursuits, etc.

A particular form or stage of civilization, as that of a certain nation or period:
‘Greek culture’.
Development or improvement of the mind by education or training.


Time Line

1733: Chester Moore Hall combines crown and flint glasses to create the first achromatic objective.

1758: John Dollond patents the design and begins commercial production of achromatic telescopes. In the decades that follow, these compact new instruments greatly aid mankind in matters as diverse as navigation, surveying, leisure and military applications.

1814: The brilliant German optician, Joesph von Fraunhofer, identifies 560 spectral lines in the solar spectrum using a small achromatic refractor of his own design, thus establishing the powerful science of spectroscopy.

1824:  Herr Fraunhofer, having developed new ways of making high-quality achromatic lenses, builds the largest telescope in the world, The Great Dorpat Refractor, and mounts it on a state-of-the art equatorial mount with clock drives. The instrument revolutionises professional astronomy. F.G.W Struve uses the telescope to conduct his grand survey of double stars, discovering 3134 new pairs.

1829: Johann Heinrich von Mädler, using a 9cm Fraunhofer refractor, constructs the first map of the planet Mars.

Admiral William H. Smyth establishes a private observatory at Bedford, England housing a fine 5.9 inch achromatic refractor by Charles Tully.

1834: With the same telescope, Mädler and Wilhelm Beer complete the first exact map of the Moon.

1838: The German astronomer Friedrich W. Bessel uses a modified Fraunhofer achromatic objective of 6.2″ aperture to establish the parallax of the star 61 Cygni, thereby elucidating the mind boggling distances between the stars. Recognising its significance, Sir John Herschel said of Bessel’s work;

[It is] the greatest and most glorious triumph which practical astronomy has ever witnessed.

1844: Admiral W.H. Smyth publishes his Cycles of Celestial Objects.

1846: The outermost planet, Neptune is tracked down and confirmed to exist with an equatorially mounted achromatic refractor by Fraunhofer.

Carl Zeiss of Jena, Germany, founds his optical company.

1847: Alvan Clark of Cambridge, Massachusetts, USA, establishes his telescope making business.

1851: George Biddell Airy installs a new achromatic transit circle at Greenwich (8 inch f/17 specification). Work with this instrument establishes the Prime Meridian, dividing the world into Eastern and Western hemispheres.

1855: Thomas Cooke of York, England begins building fine refracting telescopes of ever increasing size.

1857: Jesuit priest and astronomer, Angelo Secchi, employs 16.5 and 24.5cm achromatic refractors at the Collegio Romano, Rome, to conduct the first visual spectroscopic survey of the stars, allowing him to subdivide stars into four spectral classes.

1864: Using an 8-inch Clark refractor, English amateur astronomer, William Huggins solves the riddle of the nebulae. On the night of August 29, his diary records, “I turned the telescope to a planetary nebula in Draco (NGC 6543)…. I looked into the spectroscope. No spectrum such as I expected! A single bright line only!” Huggins had shown that this was not an unresolvable grouping of stars, as was widely believed, but a gaseous object.

1867: Having used a number of fine achromatic telescopes, the eagle eyed British observer, William Rutter Dawes, establishes his so-called Dawes Limit in regard to the resolution of double stars. That visual limit is still the best empirical formula available to astronomers today.

1868: British amateur astronomer, Richard A. Proctor, publishes his highly popular astronomy text: Half Hours with the Telescope. The book is written around what can be seen in a modest 3-inch achromatic refractor and is very well received by a growing number of amateur astronomers across the British Empire.

British amateur astronomer, Norman Lockyer discovers helium using a fine 6″ Cooke refractor.

1870: S.W Burnham acquires a 6 inch Clark refractor to begin a systematic survey of double stars.

1873: Burnham publishes his first work. An article appears in the Monthly Notices of the Royal Astronomical Society entitled, Catalogue of Eighty One Double stars discovered with a six inch Alvan Clark refractor. It is a stunning piece of work by anyone’s standards and establishes him as the greatest double star observer in history.

1877: Asaph Hall, staff astronomer using the 26-inch Clark refractor at the U.S. Naval Observatory, discovers the two tiny asteroid moons of Mars – Deimos and Phobos – during the August opposition.

The same instrument is still in active service.

1880: The great era of planetary study is in full swing, with essentially all of the lunar and planetary features sought out by amateurs today having been discovered and characterised by skilled observers using the classical refractor. Bolstered by the bogus theory of Darwinian evolution, some notable astronomers – Schiaparelli & Lowell in particular – sensationalize the planet Mars as the likely abode of intelligent extraterrestrial life. Other observers of note; the Christian astronomer, Edward Emerson Barnard, in particular, express scepticism about these claims, calling for intellectual restraint in making such audacious remarks.

Pennsylvanian, John A. Brashear, founds his optical company.

1886: The French brothers, Pierre Paul Henry and Mathieu Prosper Henry, produce the first photographic images of Jupiter and Saturn through an achromatic refractor of their own design.

1888: The Great Lick Refractor, with its monster 36 inch lens, sees first light. Staff astronomer Robert Grant Aitken et al use the instrument to achieve hitherto unheard of feats of resolution.

1891: The Henry brothers and Paul Gautier complete the Great Meudon photovisual refractor. With an aperture of 33 inches and a focal length of 53 feet, La Grande Lunette becomes (and still remains) the largest refractor in Europe.

1892: E.E. Barnard uses the 36-inch Lick refractor to discover the tiny (mean radius 83 kilometres) Jovian satellite, Amalthea – the last satellite to be discovered by visual means.

1897: The largest refractor in the world, the 40-inch at Yerkes Observatory, William’s Bay, Wisconsin, sees first light. The limitations of the refractor design are reached, causing all future telescope builders to consider larger reflectors over their refractive counterparts.

1900: S.W. Burnham publishes his magnum opus, A General Catalogue of Double Stars, consolidating the prestige of the classical refractor in the noble pursuit of double star astronomy. A veritable treasure trove of truth, 1290 new pairs are documented.

1909: New observations made by the world’s foremost visual observers, E.M Antoniadi, using the superior resolving power of the 33 inch refractor at Meudon, France, and the work of E.E. Barnard, working with the largest refractors on the planet in America, disprove the fanciful canal theory of Lowell, suggesting that they were instead optical illusions.

In the same year, the American amateur astronomer, William Tyler Olcott publishes his, In Starland with a Three Inch Telescope.The work becomes highly popular among amateur astronomers equipped with a small classical refractor, across the literate world.

The three inch refractor proves especially popular with the ‘gentleman astronomer,’ like this model, owned by Albert Einstein – a telescope he brought with him to America from Germany.

1911: Leading British astronomer, T.E.R Philips, pays a visit to Meudon Observatory, Paris, where he describes the view of Jupiter though the great telescope.

1912: Using the 24 inch refractor at Lowell Observatory, Arizona, Vesto M. Slipher obtains spectra of some nearby galaxies and in so doing notes that their spectral lines are shifted toward the blue end of the spectrum (for M31) or (for other galactic neighbours) towards the red end of the visible spectrum. Thus, Slipher discovers the phenomenon of the ‘redshift’. More spectra obtained with larger reflectors lead Edwin Hubble to enunciate that the Universe is expanding and is therefore not eternally old as was widely believed. The cosmos had a definite beginning in space and time.

1918: Robert Grant Aitken publishes his book, The Binary Stars, in which he announces that the Lick refractor could resolve equally bright pairs down to an incredible 90 milliarcseconds. He offers a new formula for these pairs; 4.3″/a beating the Dawes formula 4.56″/a, where a is the aperture in inches.

1925: American amateur astronomer, Leslie Peltier, uses his 6″ f/8 achromat, a.k.a the Comet Catcher to discover his first comet. Peltier would go on to use the same telescope to discover many more variable stars and comets

1933: British actor and amateur astronomer, Will Hay, uses his 6″ f/12 Cooke refractor at his home observatory in North London to discover Saturn’s Great White Spot.

1946: Walter Scott Houston begins writing a monthly column on deep sky observing for Sky & Telescope magazine. Houston employs his favourite instrument; a 4-inch Clark refractor, to view the majority of objects he showcases in his Deep Sky Wonders, which he continued to write until his death in December 1993.

1954: With World War II over, the US Optical company Tanross (later Tasco) is established as a major importer of fine Japanese optics. Many amateurs cut their teeth with beautifully crafted 60mm refractors but their larger aperture refractors remain prohibitively expensive for most.

1960: Fuelled on by the Space Race, many new optics houses emerge offering the amateur finely crafted lenses. High quality achromatic refractors are marketed by Swift, Unitron, A. Jaegers, Sears, Mayflower and( the much older) Broadhurst-Clarkson.

1981: Stephen James O’ Meara uses the 9 inch Clark refractor at Harvard College Observatory, MA, to make the most accurate timing of Uranus’ rotation period before the arrival of Voyager 2.

1987: D&G Optical, Mannheim, Pennsylvania, begins production of fine achromatic lenses and complete telescopes.

2004: The first econo-ED refractors are heavily marketed which promise to take the observer ‘to a whole new level of experience’. Nothing new is actually revealed with these telescopes however and yet the consumer is forced to pay more and more to receive less and less.

Interest in achromatic refractors begins to wane, despite huge strides to reduce the cost of their production. Advances in computer optimised production techniques offer the amateur finely figured achromatic lenses that are generally superior to the finest ‘antique refractors fashioned by the famous 19th century opticians and at a price that almost everyone can afford.

2005: Dr. Mike Palermiti, a professional in the field of optics, publishes a short article where he stresses that the use of expensive exotic glasses in apochromatic refractors is completely overkill for visual use and that skilled observers have no need to over indulge. His advice is ignored by the consumers of fancy glass.

2010: The lead author publishes his book on refractors, raising awareness amongst the amateur community of the importance of achromatic refractors that had satisfied their users for decades and centuries.

2011: American observers, John Nanson and Greg Stone launch their superlative website, Best Doubles, dedicated to visual double star observing. John, a.k.a, Der Admiral, employs classical refractors of various sizes in the pursuit of his colourful celestial booty.

2012: An ornate, all-brass refracting telescope, fashioned by master British instrument maker, I.R. Poyser is chosen as the principal gift to the citizens of Japan from the British people to commemorate four centuries of friendly diplomatic relations between the two countries.

2012 to 2015: The lead author unveils a string of articles highlighting the remarkable properties of classical refractors, using a wealth of science and history to support his conclusions.

The lead author uses his Astrophysics Traveler to satirise the state of affairs in amateur astronomy.

A thriving online community of amateurs – observers and collectors – maintain an active presence discussing the charms of the classical refractor. Many more amateurs begin collecting these precious instruments from yesteryear for pleasure.

A Spokesperson for the US Naval Observatory explains why the classical refractor is still the best choice for double star astrometry.

New companies offering the classical refractor emerge. Skylight (employing a 4 inch f/15 lens designed by Al Nagler’s Televue), Moonraker, iStar and FrTelescopes.

Sky & Telescope favourably review a very fine 102mm f/11 achromat by Astrotelescopes – the first such review in over a decade.

The Oddie II Telescope, featuring a modern achromatic lens, is reinstated on Mount Stromlo Observatory, Canberra, Australia in the aftermath of a terrible bush fire.

The Celestron C102 4-inch f/10 achromat goes on sale for less than $100. In a frenzy, many savvy amateurs acquire one and almost universally report excellent image quality.

Restorative work begins on Lowell Observatory’s historic 24-inch Clark refractor.

2016: The lead author sets to writing his new book: Tales from the Golden Age.

The lead author looks back on the rise in popularity of the achromatic and, with great personal satisfaction, sees that it is good.

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                                              My Favorite Telescope

                                         by Terra Clarke, Kentucky, USA

I’ve collected quite a few classic telescopes over the last few years since I retired from a career in higher education. So when I was asked to write an essay on my favorite telescope, I briefly found myself in something of a quandary over which telescope to write about.

My collection initially came about quite by accident, or what Jung would call, synchronicity. I had just read an article in an astronomy magazine extolling the virtues of the classic 60mm long focus achromat. That had set me to thinking that I really would like one to complement my modern 80, 102, and 120mm refractors. (A 60mm refractor was the first telescope I had ever owned.) Then, while I was out of town, my partner called me on my cell phone to tell me that she found one for me at a thrift store. It was a 60mm equatorially mounted Monolux in its original wooden cabinet, and it was waiting for me on the dining room table when I came home. It was very dirty, but almost totally complete. It just needed a good cleaning and a couple of easily replaceable parts (dust cap and visual back). When I cleaned it up, I saw that it was a real beauty, made by Royal Astro. We set it up in a corner of the dining room a display scope, but we soon found that the scope performed wonderfully out on the deck under the stars. Small, lightweight, and very functional, it was a perfect grab and go telescope, ready to exit the kitchen door in an instant. It put up picture-perfect, defraction-limited views.

Terra's little Mayflower ready to be fed star light.

Terra’s little Mayflower ready to be fed star light.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

There is much to recommend in these old classic achromatic refractors. Aside from their beautiful craftsmanship they typically have excellent optics and near apochromatic like performance. They deliver crisp images of superb contrast; stars look like diamonds cast on black velvet. Their extensive focal depth make it easy to achieve sharp focus and excellent performance can be attained with simple eyepieces (orthoscopics, Plossls, Kellners, Erfles). Showing pinpoint stars and sharp well defined Airy disks; they are a delight to use under conditions of poorer “seeing” and light polluted skies. They are quick to achieve thermal equilibrium and are wonderful for instruments for viewing double stars, planets, the sun and moon in an urban environment.

That 60mm Monolux wet my appetite for another, larger classic telescope and in a short time a beautiful near mint, complete, 3 inch Sears just fell into my lap for very little money. I had wanted a scope like this when I was young and now, many years later, was my chance to get one. That is how I began as a vintage collector. I had always loved Unitrons so the 60 mm and the 3 inch were added next to the collection. Of course, no collection could be complete without a Zeiss, and when I found a nice Telementor T1, I acquired it as well, and then a T2. At this point, I could see that I had not one hobby, but two. I was not only an amateur astronomer, but also a telescope collector. I found a little 80mm Unitron spotter in great condition, at a great price, and I already had a spare Unitron alt-azimuth mount for it, and so I got it. Then another 60mm Unitron, (a very early one) came my way, and ultimately a fantastic old Unitron 4” equatorial, which I had the amazing good fortune to receive as a gift from a wonderful and generous person that I met through the hobby. Over the past several years a fairly rare 3” refractor made by Goto Optical of Japan in the 1950s and a classic Edmund 4” F15 refractor have come my way as well. I love little 60mm refractors, and with limited storage space, they don’t take up much room so when I found a complete little 50-year-old Tasco 60mm, wooden cabinet and all a thrift store for 20 dollars I picked it up. Most recently a very lovely, and totally complete 60mm Swift telescope in nearly mint condition was found while on an autumn weekend trip several states away.

Most of these telescopes came to me serendipitously. It was almost as if they had chosen me, rather than I choosing them. Often I made friends in acquiring them. I learned their stories. In some cases, we took long road trips to get them. But the most amazing journey of all was when the first telescope I had ever owned came home.

The 50s and 60s were such a great time to grow up. It was the “atomic” age, we were in the middle of the space race, it seemed like there was a different science fiction movie to see every week, and if you were a kid who loved science, these were heady times indeed! We even had a bright comet. I will never forget Comet Ikeya-Seki back in my first astronomy winter of 1965. In the 1960s everything was analog, we appreciated what we had, and we made the best use of it. We learned the night sky, learned to find what we wanted to see by star-hopping and using binoculars and star charts, and sometimes using setting circles. If the scope was driven, it was typically only in R.A. We looked in awe at the astronomical object we saw rather than critiquing the view with regard to chromatic aberration, pinpoint star patterns across the field, etc. And I should add that in my opinion anyway, the skies were much better then, fewer contrails, and less light pollution. It seemed to me then that is was much more about the sky and much less about the equipment- or perhaps that was just the exuberance of youth and living in the “space age.”

I had gotten interested in astronomy when I was 14 when one summer evening we went to visit some family friends who lived in the mountains of Southern California near where we lived. We were there for dinner and their son, who was about my age had a 3″ Edmund reflector. (The Space Conqueror I believe). After dinner, we went outside to look through it while the parents visited. From that point on I was looking up. I got a copy of the little Golden Book, The Stars, by Zim and by October, I had talked them into getting me a pair of binoculars, some Japanese 8x40s that my dad ordered from one of his sporting goods catalogs. I also got a copy of The Stars by H. A. Rey and I was off and running. At Christmas I got the Peterson Guide and by the following birthday, I got my first real telescope. It was a Japanese-made (APL) Mayflower 60mm x 700mm yoke-mounted alt-azimuth refractor. I got it in 1965 for my 16th birthday. I had wanted a 60mm Unitron alt-azimuth refractor (Model 114) but that was out of the question, the Mayflower cost about half as much at our “big box” store back then and we were a union, working-class family. I remember that crisp October night many years ago like it was yesterday. I even remember it was a Saturday. I was not disappointed! The first thing I looked at was Saturn! Then I split the “Double-Double” as Lyra was going down. I stayed up late to see the Andromeda Galaxy, the Hyades, the Pleades, and then the Orion Nebula and the Trapezium! Zowwie! I was in love! I was hooked on Astronomy for the rest of my life after that. I even also saw my first comet with that little telescope two months later; Comet Ikeya-Seki in December of 1965.

That little telescope knocked around with me for what seemed to be forever. I always kept it because the tube was built like a tank and the objective was superb. Over much of that time it was often my one and only telescope. It is very portable and presented amazing views for its aperture. The Mayflower always stayed in its box when it wasn’t being used so it remained in good shape and was always ready to go, and go it did. It was the family scope, the travel scope, the grab and go scope for over 30 years. My two daughters grew up with it. With it we saw solar and lunar eclipses, comets, the transit of Mercury, and the S-L impact scars on Jupiter. I indoctrinated my two girls with that telescope to the point that one of them, now a filmmaker has made an astronomy themed Sci-Fi short film and the other one named her son Orion. Oh the memories that scope holds! The wooden box and the wooden tripod legs had been refinished a time or two due to all the use, The tube has had to be touched up, but it is still dent and ding free; the optics pristine.

Eventually I got a couple of more modern refractors of greater aperture and the little scope got less and less use. Then, about 10 years ago in one of life’s upheavals, I loaned the Mayflower to some good friends and moved out of town. Up until a couple of years ago, I thought it was gone for good. Then strangely I received a phone call from the friend that I had loaned it to. She said she had run across it in her attic, that it was unused and unneeded and was calling to ask about its disposition. I asked her if I could swing by her place the next time I was in town and get it, and she said sure. So the little telescope came home. It was kind of a sad sight. The old yoke mount that had been showing its age for some time was finally shot. The gear housings for the worm gears were broken. The tiny finder was gone, so was the accessory tray. But optically, it was still perfect; the 0.965” eyepieces, diagonal, and other accessories were still present, and the tube and focuser, the wooden box and legs still in good shape. I resolved to put it back in good order.

I had some rings and a mounting plate made for it, and I bought a Unitron alt-azimuth mount, tripod and spreader from a friend and member on here. I also still have a vintage GEM that I bought from Edmund Scientific Co. a year after I got the Mayflower. I have placed that mount on the original Mayflower legs so my little first telescope can ride on this mount too, just as it sometimes did, many years ago. I also put a 6 x 30 finder on the little Mayflower that was way better than the tiny original, and I added a 1.25″ Vixen visual back so that it can use a larger prism diagonal and 1.25” orthoscopic, Plossl, and Kellner eyepieces. I use the little telescope a lot these days for quick solar viewing out on my deck. Recently I was using it to view sunspots with a 1.25” Intes white-light solar diagonal. It held at 93X just fine with a 7.5 mm Plossl eyepiece. Not bad for daytime seeing.

I lost my parents in 2000 and 2001. That Mayflower is especially important to me for that reason. Sometimes, it just takes a while to realize the true worth of things, but as my mentor in grad school used to tell me, “to soon we get old, to late we get smart.” I once threw it over (euphemism) for a 4″ fluorite Vixen, which is now long gone. If someone now offered me the Vixen back in return for the Mayflower, I’d have to say no. The little telescope has gone through some changes, but it is still basically the same little scope with that wonderful APL objective that I have seen so many wonderful things with over the years. And yet, it’s far more than just a telescope. It’s a talisman and a time machine. I will always remember my mom coming out from the kitchen to the backyard to take a look at what ever I was looking at. I can use it now and see her standing right beside me. It will be the last scope I ever let go. Yes, I thought I had lost it but got it a few years ago. But I never realized just how valuable it was to me. I do now, and when I got it back, I vowed it would never again leave me.

The exquisitely made focuser on Terra's Mayflower.

The exquisitely made focuser on Terra’s Mayflower.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For me, it puts me in touch with those feelings and memories of what things looked like, felt like that first autumn and winter nearly 50 years ago when I first saw Saturn’s, Jupiter’s cloud belts, Venus in a crescent, the sparkling Pleiades, the distant Andromeda galaxy, and the glow of the Orion nebula through a telescope as a kid. Its pure nostalgia, and appreciation for the past becomes more and more important to me as I advance into the future. Sure I have modern telescopes (which if I admit it) present better views maybe, but they don’t give me the same feeling when I look through them.

All telescopes are time machines in that they allow us to look back into the past as we span distances across our galaxy and beyond. But classic telescopes are real ‘way-back machines’ that put us in touch with long past amateur and professional astronomers who discovered so much when looking through these elegantly simple instruments; and they put us in touch with our own past as well. For me, when I look through the “little telescope that could”, I am again that 14 year old kid that gazed through the telescopic looking-glass and was filled with wonder and awe. And I can here my mom softly whisper in my ear: “My oh my, just look at that!”

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                        The Visual Virtues of Long Focus Achromatic Refractors

                                     by John Nanson ( Der Admiral), Oregon, USA.

It took me a few too many years to discover the visual magic served up at the eyepiece end of a long focus refractor. Like many others, I was pulled toward expensive short focal length APO’s, primarily because they’re widely advertised, and also because for many years the vast majority of on-line comments about achromatic refractors was negative. Once I got my hands on my first achromatic doublet, a used 80mm Stellarvue Nighthawk that was built like a tank and weighed about as much, I discovered the constant refrain about the horrible CA affecting the visual image in an achromat was way off the mark. One double star observing session was enough to discover the filter I bought to lasso the out-of-control CA was about as unnecessary as a heat lamp in a desert at mid-day.

John's beautiful but inexpensive Mizar 80mm f/15.

John’s beautiful but inexpensive Mizar 80mm f/15.

 

 

 

 

 

 

 

 

 

 

 

 

If I remember correctly, the SV Nighthawk was around f/7, so it doesn’t quite qualify as a long focus refractor, which for the purposes of this article we’ll define as f/10 or greater. Shortly after discovering an achromatic refractor wasn’t a metal tube of visual horrors, I came across an old 80mm Mizar refractor that was sporting a 1200mm focal length Carton lens – as in f/15. It didn’t take more than a few days for the telescope to find its way to my front door, secured in an old wooden box that felt like it was filled with lead weights. The one thing that scope lacked was a dew shield, so a trip to the local hardware store netted a piece of black PVC pipe that fit perfectly after some minor alterations.

 A double star that was on my uncooperative list at the time was Theta Aurigae(magnitudes of 2.60 and 7.20 separated by 4” as of 2009), which I believe Neil had first mentioned to me. I had made several attempts to pry apart the primary and secondary with a couple of other larger scopes, but the seeing was so shaky and nervous each time that I never came anywhere close to succeeding. One evening shortly after dusk as Aurigae was hovering in the west, which typically is a rather turbulent part of the sky from my location, I pointed the Mizar tube at Theta just to take a quick peek. I really didn’t expect to see the secondary, but once I realized the seeing was remarkably stable, I increased the magnification until a dot of light budded into view on the rim of the primary. I stared for about fifteen minutes as that impossibly small dot of light clung to the primary as though it was afraid to let go. As the seeing deteriorated to its normal uncooperative self, I sat riveted in place at the eyepiece until the primary swallowed the secondary. I doubt a photograph would have done justice to what I saw, but it doesn’t really matter since the image is etched permanently into one of the many double star crevices in my mind. Since that time, I’ve cracked Theta Aurigae with larger scopes, but the 80mm Mizar view is still the one called up by my memory when I think of that double star.

Another long focus refractor that landed on my front porch is the Skylight 100mm f/13, also armed with a Carton lens. Whereas the 80mm Mizar was less expensive than the SV Nighthawk had been, the Skylight refractor represented a considerable investment. I hesitated on that one for that reason, but once I had it out of the box and on a mount, I became as attached to it as my right arm. It didn’t take long for the 100mm f/13 Carton lens to reveal its magic.

John's ornate, neoclassical 4-inch Skylight F/15.

John’s ornate, neoclassical 4-inch Skylight F/15.

A double star that lures me back again and again is Rasalgethi (magnitudes of 3.48 and 5.40 separated by 5”), located south of the Hercules keystone. Tough it certainly isn’t, but beautiful it most definitely is. The primary is a rich orangish-red hue, and the secondary seems to be a toss-up between pale blue and pale green. I’ve looked at it more times than anyone can count, but the view I had in the Skylight f/13 on a night of better than normal seeing literally welded me to my chair. When I first looked into the eyepiece I was standing up, but as soon as my thirsty eyes drank in the image, I dropped into my chair and melted into it. Both stars were unusually sharply defined – as round as round can ever be — and etched into the black background like multi-colored slivers of glass brought to life by sunlight streaming through a stained glass window. I sat and stared so long I lost track of time. As each single scintillating second of that remarkable view soaked into my memory, I was very conscious of looking at something quite unique and special.

When I think of experiences like the two I just described, I conjure up images of S.W. Burnham sitting at his six inch f/15 Clark refractor. He discovered well over 1000 double stars with that instrument, more than a few with difficult sub-arcsecond separations, partly because he had eyes as sharp as an eagle, but also because he had a very capable instrument. And it was an achromatic doublet, too. Which is argument enough that an expensive triplet is far from necessary for either the casual or the serious visual observer.

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                                                    When Life Takes a New Turn

                                                    by Rutilus, Yorkshire, England

Life can be a funny thing. You can travel and experience many wonderful things, and yet more often than not at some point, you always seem to return back to where the spark for adventure was first ignited.
For me, such a thing happened regarding my observing preferences and in particular the type of instrument I use. When I first started to observing the night sky with telescopes, I was using achromatic refractors. These instruments served me extremely well for many years. Then I caught the apochromatic bug which resulted in my purchase of a lovely102mm f/8 Triplet APO scope. I used the APO for around seven years, and was extremely pleased with it.
Mike's homemade 6" f/15.

Mike’s homemade 6″ f/15, which can be broken down easily for transport and storage.

 

 

 

 

 

 

 

 

 

 

 

 

 

Then one day (just by accident) I found some old drawings that I had made of the planet Jupiter and Mars. What struck me, was that the old drawings made with the achromatic ‘scopes.
All appeared to show the same amount of detail as I was observing with my Apo ‘scope.Then, as if by fate, the opportunity to acquire a very well made 100mm f/13 achromatic doublet lens came my way. The lens was purchased and fitted into a tube and lens cell that I made myself. This achromatic scope was used extensively side by side with my APO scope. I was so pleased by the eyepiece views given by the achromatic instrument, I actually went ahead and sold the APO. The money from the sale went into a 150mm f/15 achromatic lens and heavy duty driven equatorial mounting.
The 6 inch achromat has proven itself to be an excellent instrument, showing a great amount of planetary and lunar detail. One of my very first interests in astronomy was the study of double-stars, and it is here that the 6 incher truly excels. This ‘scope takes high powered views of difficult, unequal doubles in its stride. I have been extremely impressed by the star-splitting qualities of this lens.
The 6-inch glass quietly at work.

The 6-inch glass quietly at work.

 

 

 

 

 

 

 

 

 

 

 

 

 

When I started observing the night sky way back in the 1960s, the idea that one day I would own an excellent 6 inch refractor seemed nothing more than a pipe-dream back then.
Yet, here I am with such a ‘scope in my own back garden. Looks like I  have gone full circle and starting to enjoy again the excitement of those early days.

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                                The Story of Andromeda, my 5-inch D&G

                                        by Dave Tinning, Central England

I have always loved long focus refractors and they don’t come much better than D&G American made lenses.  The lens on this scope is pristine. The scope came from Osborne Optics in Newcastle, but I’m unsure whether this was a D&G built OTA or a UK built tube around the D&G lens. I suspect the latter is the case but I hope to ascertain for sure by contacting D&G themselves.

5” of unobstructed high quality glass.

5” of unobstructed high quality glass.

This ‘scope had been in storage for most of the past c12-13 years since it was bought by the seller. It has been securely kept in a large, robust shipping tube with the lens and focuser securely sealed. It has a few very minor marks on the tube but is essentially as new. It has a simple, but good quality and very smooth R&P focuser which can accept both 2″ and 1.25″ eyepieces. It came with a nice black 50mm finder but I have attached my own Stellar Vue  50mm RACI which I think suits the scope well.

My main concern was mounting the scope. My trusty CG-5 is a good mount but this is a very large OTA and really and truly it would be best on an EQ6 – something I can’t afford at this time; however, with the upgrades I have added to the CG5, including the ADM puck and saddle upgrade, and a longer counterweight bar, with a heavy duty WO mounting plate, the set up is more rigid than I could have hoped for. The OTA itself weighs only around 20lbs.

I almost sold this mount recently and am so glad I didn’t now! I hope you like the pictures and I will post a proper first light once I get one! I have high hopes of this scope for the bright planets and double stars.

In June 2014, I went to the Astro show in Leamington and met Mark Turner of Moonraker Telescopes. I had a good chat with him, especially about the focuser, and possible binoviewing. The standard Japan made R&P focuser was fine, quite smooth, but I always felt that the lens could take higher powers than I could properly use with the original focuser, with very fine adjustment being critical at powers of ~300x or more. Mark recommended the Moonlite range (in fact I’d had an old one a while back and knew that they are great units), and advised that he could machine me a new flange plate for the back of the OTA tube, so that a Moonlite dual speed focuser could be attached to it.

 

The other issue we discussed was in-focus. I knew that binoviewers could give great views, but the downside for me was always that they normally need to be used with a Barlow lens on a refractor. Since this is a long scope (1905mm focal length), even a 10mm eyepiece delivers x190 magnification, so the thought of doubling that or more with a x2 or x2.25 Barlow was not attractive to me. In the past I’ve always resisted chopping tubes to gain in focus; this time it was different. I felt that ‘Andromeda’ (as I’ve called the ‘scope) was worth the effort, and also as I get older, I know my eyes aren’t quite as good as they were years ago, and I just felt that using both eyes to view would be more relaxing and help me see more.

So, having all this going around in my head, I thought about it for some weeks and then decided to go for the focuser upgrade with Mark’s flange, to see how that was. I was genuinely delighted with the new focuser, but again in the few chances I had to use the scope with it, I still hankered to be able to use a binoviewer without a barlow. So I again spoke with Mark and decide to go the whole hog and send the whole tube (all c2metres of it!  to him in London to completely revamp it for me. Here is what he did:

  • Chopped 130mm off the tube and square off both ends to ensure the lens and flange would be completely square to the focuser.
  • Drilled new finderscope holes either side of “straight ahead”, to allow the use of a finder on either side, or one each side, as I wished.
  • Sent tube to powder coats to be stripped, repainted with multiple coats, including dewshield.
  • Completely rebuilt new ray traced knife edge baffles (x3) with retaining rings and fit (the old ones were up to 10mm out of square alignment)
  • Completely flock the whole tube with Protostar material, including the dewshield. It’s now like the black hole of Calcutta down there!
  • Reshaped the base of Tal finder mounting bracket to fit the OTA perfectly

I received the tube back about 2 weeks ago and put her all back together again last weekend. I found a lovely vintage Yamamoto (Perl brand as sold in France) 60mm F6.6 refractor to use as a super finder, and it fits onto the Tal finder bracket perfectly.

For my first light, I turned to Saturn, a favourite object of most of us. Sadly, this year, it’s not been well placed, being rather low down: here in the English Midlands, although my local light pollution isn’t too bad, we are surrounded, within 10-25 miles, by a ring of large cities including Birmingham, Tamworth, Coventry, Leicester, Derby and Nottingham. So there is a ring of orange glowing around us in all directions, and I would judge that only the highest c40% of the sky is relatively dark and unaffected.

This means that Saturn was caught in that glow quite noticeably, but I have to say that, given that fact, the views were beautiful. A very clear Cassini division stretching all around the planet, a clear equatorial thick belt, and at least one other suspected at lower powers. I could also see two moons (I think Titan and Rhea) clearly, and another suspected.

Contrast was good, given the skyglow, and there was no glare from the planet, no light scatter, and no CA whatsoever.

I then turned to Delta Cygni, a favourite close double and not at all an easy split in anything less than a good 4” lens. In the D&G it was so easy! Clear, dark sky between the primary and it’s companion, (most of my previous views in 4” scopes tended to show the secondary sitting on the diffraction ring of the primary, but not here..). I also felt that the primary showed a suggestion of colour (very pale blue) which I had not noted before. All this bodes very well indeed for the scope to be a consummate star splitter!

Dave's magnificent 5 " f/15 D&G refractor.

Dave’s magnificent 5 ” f/15 D&G refractor.

Next up was the double double in Lyra, which by now was fairly high up. The striking thing here was the contrast, simply superb, with a jet black sky in my Leica Zoom at c x150, and two lovely double bulls’ eyes, each pair at right angles to each other.

Close by of course is Vega, that searchlight of the summer skies, and I wanted to see how much Chromatic Aberration would be visible: after all, this scope is an achromat. Well, I’m delighted to report that there is only the slightest tinge of violet from Vega; overall impressions are of an almost white, bright star with just a hint of violet which is actually quite pleasing. The same can be said of Deneb, in Cygnus close by, and even less obvious, since the star is not as brilliantly bright as Vega.

One of my favourite stellar quick view sights is Mizar in Ursa Major, and this one is truly lovely at low power in the D&G…(I should say here that “low power” is a bit of a misnomer here..at F15 with a 5” lens, the scope has a focal length of 1905mm, so my lowest power eyepiece, at 40mm is about x47 – not truly a low power experience, but as good as it gets with this type of scope. The contrast is what you notice with this scope, and the higher the magnification goes, the blacker the sky background gets.

The lunar surface is jaw-dropping in this instrument using the Baader Maxbrights and Takahashi LE 18mm pair.

This is not a deep sky scope, but, like anyone else, I will want to look at everything I can with Andromeda, and so I turned her to M13, the showpiece globular cluster in Hercules, on one of my all too short sessions: the high power nature of this long refractor actually enhances the contrast views you can get of quite small objects such as M13 in Hercules. Moreover, the Leica Zoom gives it’s widest field of view at higher powers, so I was able to view M13 at around x260, with a black background peppered with myriads of scintillating points of light which seemed just to pop up in ever increasing numbers, the longer I looked at the object. Truly beautiful!

The truth is, I don’t feel that, as yet, I have scratched the surface of this scope’s potential.  I’m a happy chappy and so pleased to have Andromeda sitting, waiting, ready to cruise the heavens with me!

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                                    The Aesthetic Joys of Long Focus Refractors

                                         by James Curry, St. Louis, Missouri, USA

My observing has evolved to the aesthetic presentation being “the all” of an evening’s time out. I enjoy a twilight setup of a long tubed refractor, its’ light collecting element well above the lingering ground effects. If I’m using a manual equatorial, first I get the scope carefully balanced with tube weights trimmed, mount clutches adjusted followed by a few star checks to see what the atmosphere is like. A walk around the scope is next, alternatively taking in the beauty of the instrument with glances skyward to monitor the firmament’s darkening. Taking my seat I glance around to be certain I have what I will need at hand; notepaper, pencil, light, etc. A few minutes for a 2 element achromat, perhaps twenty or so minutes for my 4 element Petzval to stabilize and I’m taking advantage of that atmospheric null time of steady air for solar system observing. Assuming a now stable weather system has ensconced itself over the region, this null time can vary in length but can stretch out to 2-3 hours. If it’s a good night 50x per inch is in store. Anytime I can reach above 50x per inch is a great night when observing from the middle of the continent. Truth be told, 125x – 175x is the normal maximum useable magnification for solar system studies no matter the aperture.

I spent decades with reflectors. My last one, a 10” Cave, sits forlorn in my man cave. Moving up the scale 4”, 8”, 12.5” I realized my sweet spot was in the 8”-10” range. I had a near religious experience on M42 with my 8” Parks during a cold winter’s session. But when it was time for a new scope I looked into the refractor market.

My first refractor was a Vixen 140 Petzval. Gone were the diffraction spikes, soon forgotten was the collimation issue and immediately noticed was the quick setup and temperature acclimation providing reliably steady views for an entire evening.

Jim's first refractor

Jim’s first refractor

Tube currents became a forgotten malady. I took up the H400 challenge with this scope and methodically worked my way through it over two years. Fainter members of Markarian’s Chain, Stephan’s Quintet and brighter members of the Deer Lick Group and other challenge objects were checked off my observing bucket list with this scope. On nights of crystal transparency I was detecting galaxies to 13.5 magnitude, on nights of rock steady atmosphere Jupiter looked like hand painted calligraphy on the lens.

Next on my refractor journey was my 4” f/12 Istar build. 6 months or so of design combined with on-off shop time and I machined up the fittings to mate lens cell and focuser to my powder coat painted tube. The f/12 ratio seemed to provide a steadier, “smoother” image than the f/5.7 Petzval. Star testing it on its first night in public our club optical expert declared the lens “functionally perfect”. “This looks like it was turned on a lathe” he declared as he released the chair to anxious club members waiting their turn. The lens is advertised at 1/6 wave and he said it’s there.

Jim's 6" f/12 home build.

Jim’s 4″ f/12 home build.

Building on this initial success my follow-on project was a 6” f/12  build. Again, functionally perfect achromatic optics provide picture perfect views. Within minutes of first light I dialed in 300x on close double stars in Cassiopeia revealing perfectly concentric rings, clean hairline gaps and with the lens 7’-8’ off the ground an un-quivering view. One memorable evening in that early nightfall null of temperatures I was able to get a steady, detailed 360x on the moon.

The 6 incher in the field.

The 6 incher in the field.

Somewhere along this refractor journey I stumbled upon a 60mm Unitron rescued from the dump. Within a white tube permanently discolored by grease stained hands lay an optical treasure. This is the little telescope that could.

As a challenge one frosty winter’s eve I checked my Jupiter chart and realized there would be a double moon transit. I felt confident the shadows would be prominent but what amazed me was both moons remained in plain (concentrated) view for their transit duration. This experience whet my Unitron whistle and I’ve been on a quest to collect excellent examples of the 3” and 4” equatorials with a suite of accessories. While I still have a few, the 60mm-er’s no longer hold my interest for use observing.

Back to the aesthetic presentation theme. My 4” Unitron 155c is my “Venus” instrument, an object of admiration even set up in the house. Perfectly proportioned, I feel the Unitron line is the pinnacle of the amateur scientific instrument art. The 4” represents the largest portable scope of the line before you journey into the rarified air of the 5” and 6” observatory units. I have yet to meet an amateur astronomer whose head doesn’t swivel to the set-up of a 3” or 4” equatorial Unitron on the observing field. Even the “civilians” are irresistibly drawn to it at a public star party. The proportions are universally pleasing and the views will not disappoint. This is a telescope.

Jim's Unitron

Jim’s Unitron

Further exploring the aesthetic theme, one summer’s eve I set up next to a 16”, high end, brand name Dobsonian. Almost immediately after the lens cap was removed my 4” was throwing up etched views of Saturn with its rings and Cassini division in sharp definition at 175x, about the limit for the atmosphere that night. The 16”, after having cooled with multiple fan assistance for an hour at that point, showed a smudged, current-smeared image with no shading on the disk and ill-defined rings. We packed up about 3 hours later after a heavy dew drop. That night the dob was all sob, it never produced a good planetary view plagued as it was by a mirror that would not keep up with the slightly falling temps. It could definitely reach deeper, showing fainter stars and out-resolve me on the globular clusters but those stars were not the pinpricks they were in the refractor.

The telescope maketh the man.

The telescope maketh the man.

A combination of a pleasantly proportioned instrument and those highly acclaimed refractor views are what I mean when I say I enjoy an aesthetic presentation.

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                                                       My Achromats

                                            by Bill Nielson, Florida, USA.

As a young child in the 1950’s I was fascinated with telescopes. I pleaded with my parents for a Christmas telescope. Sure enough one showed up under the Christmas tree and I remember it as my best present ever.

It was a humble, low priced Sears offering. A short tube 60mm achro with a Barlow and a sliding eyepiece that allowed 15x-60x magnification. I loved it! Showed a great blue enhanced view of the moon. The most blue moon I’ve ever seen. The CA was bad but I loved using it to observe the moon, birds, and terrestrial targets.

At around 11 years old I had a paper route and bought a Sears 60mm with a better mount and a much superior lens. Saturn was stunning, Jupiter too. The moon was no longer blue! This was my first quality achromat.

Bounce forward 40 years or so. After owning several scopes of different types I yearned for the simple pleasure of the telescopes of my youth and the ones I couldn’t afford at the time. So now I have four achromatic refractors that serve me well. I love the simplicity and the beautiful engineering of my Polarex (75mm) and Unitron (60mm) telescopes. I also have a classic 60mm Lafayette on a sweet, perfectly matched equatorial mount. I can pick this scope up with one hand and carry it outside,
Beauty, simplicity, quality, and great optical performance are what I enjoy.

Bill's beloved Unitron kitted out for some serious fun.

Bill’s beloved Unitron kitted out for some serious fun.

Compared to APO’s, my ‘scopes stand up on their own considering price point.

I have other telescopes but my achromats are my favorite for visual, planetary, lunar, and double star observations. I use larger Newtonian reflectors for deep sky objects.

I live in a terribly light polluted urban area. The sky is milky white. However my long focus achromats deliver a dark background and near perfect star and planetary images which are very pleasing.
Some of the classics like Unitron/Polarex are collectable and demand a high price. They are highly crafted complete packages with superior mounts and accessories. They are worthy of display in any home. However there are many other small used achromats out there that are tremendous bargains. Some are almost given away at garage sales. Many have optics the equal to the expensive classics. But they usually come with less than desirable mounts. No worries, there are used and new mounts available to turn one of these great “finds” into a wonderful, cost effective telescope.

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                                              My 6” f15 D & G Telescope

                                          by Andy Jackson, Perth, Australia.

About 20 years ago I became interested in telescopes and visual astronomy. I thought that telescopes were too expensive and difficult to get as there was only one local vendor and most Australian telescope shops were on the east side of the country. My sister visited Melbourne and was able to get a set of reflector mirrors for me. They allowed me to put together my first telescope, a 110mm f7.5 reflector. At that time I was into boat building as a hobby so I made the scope out of thin ply and Australian hardwoods. It worked well enough to show me the basic sights of the night sky and gave me a passion for wooden telescopes.

As this interest developed I learnt more about the differences between reflectors and refractors. I obtained a copy of Richard Berry’s book Build Your Own Telescope. I tried making other small reflectors and had a lot of fun. Eventually I began to lust after a good refractor. At the time I could not afford an apochromat and I had read good things about D&G achromat lenses available from the USA. I followed Richard Berry’s concept for the 6” f15 in his book and added my own touches based on my experience from making the reflectors.

Andy's homebuilt 6" f/15 D&G.

Andy’s homebuilt 6″ f/15 D&G.

The telescope that resulted from all this has proved to be an exceptional instrument. It is large and bulky but performs to a very high standard and is very basic and reliable. I have found it to be ideal for the variable conditions found here in Perth. It can be set up in a few minutes and is virtually maintenance free. It holds collimation and never needs adjusting. I like the fact that it will never need re-coating unlike the reflector mirrors. I still have an 8” Meade Newtonian mirror that needs re-coating however the cost of sending it to Sydney to be re-coated is more than the cost of a new mirror.

The 6” f15 performed so well that I got the bug and kept making more telescopes for fun. I have too many now and don’t have the time or space for all of them! I have also acquired some nice apochromats up to 4” f8 and enjoy using them especially when travelling as it is not so easy to transport a long bulky refractor.

Classic books for classic 'scopes.

Classic books for classic ‘scopes.

During my ‘scope journey I have been inspired by many others that also enjoy the long focus achromat. Some great books include The History of the Telescope by Henry C. King and Epic Moon by William P. Sheehan and Thomas A. Dobbins

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The Tasco 20TE Comes Back Home

         By Mike Carman, Bellevue, Nebraska, USA

Every so often, the Midwest strikes a coupe for the patient hearted. Back in 1977 the Omaha Astronomical Society received a donated Tasco 20TE from a local MD physician. I was given the ‘scope to store in my townhouse garage for two years. At the time I was building my 6″ f/8 Jaegers and had no interest in this old “relic”. In 1979 the club attempted to sell the scope but one of the club patriarchs came forward and purchased it for $500. He then donated it back to the club around 1993. The club then put it away in storage after several outings with club members by 1995 or so. Things become sketchy owing to membership turnover and lack of records and the like. But basically the club had no use for it. Then in 2008, the 92 year old patriarch and his second wife died. The club then decided to put it up for sale again. I had re-joined the club in 2007 after leaving for personal reasons in 1982. The few members that had seen the scope weren’t real positive of its pedigree and I put two and two together and thought this must be the same scope. Sure enough it was and they agreed to sell the instrument to me for $125.

A dusty but otherwise immaculate object glass.

A dusty but otherwise immaculate object glass.

Some people can appreciate the labor of love that must go into a total restoration of a telescope like this. Others can simply be enlightened. This newly acquired telescope of mine was a nightmare. This was the result of 12-15 years of complete neglect. Membership changes in my local club and lack of records caused some problems with an accurate timeline of events.

An old dusty telescope.

An old dusty telescope needs a bit of TLC.

Anecdotal evidence suggests that this ‘scope was locked away in an inoperable ROR observatory since 1993 at our club’s rural observing site. Here follows some but not all pictures that I’ve documented.

Rusted and dust laden; the fine old equatorial mount of the Tasco 20 TE.

Rusted and dust laden; the fine old equatorial mount of the Tasco 20 TE.

Optically this scope is in a league of its own. It literally is a step above my Sans & Streiffe 76mm x 1200mm. I was viewing Castor the other night. You could definitely see the different subtle hues….and talk about diffraction rings….and this was at 400x!! The Moon was near the Zenith at half phase and I could not detect any purple in the crater shadows at 400x! Now you can say bull but I couldn’t detect any. At the limb of the Moon you could just detect that something just wasn’t quite correct about this “reflector” like image. I was simply blown away with this lens. Then I go over to the 8-inch and the stars are softer due to the seeing which had a slow boil and a much brighter view of course. The lenses have not been touched. Some dust on back and front sides but no sleeks or scratches or coating flaws.

The restored telescope ready for work.

What a beauty! The restored telescope ready for work.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thank God they received little active duty and were well capped. After a lot of extensive cleaning; the telescope was proudly displayed on its equatorial mount, where it now enjoys a new life under the stars.

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                                                A Short Tribute to Alvan Clark & Sons

                                      By John B, Mid Hudson Valley, New York State, USA

I am a great admirer of old school refractors. The 5-inch equatorial Clark I had in my possession for a number of years way back when gave absolutely exquisite images for its aperture. In fact, over the years I’ve had the opportunity to view through quite a number of the pre-Lundin era Clarks and each produced images that exceeded those found in modern-era telescopes, refractor or reflector. The very finest was the 12-inch in the possession of the late Leslie Peltier of Delphos, Ohio. With it I can only liken what one saw of Jupiter to images rendered by Hubble or modern spacecraft orbiting that planet. The view was so tack-sharp and with detail far beyond anyone’s possible abilities to draw that for the one and only time in my long observing career I got the impression I could literally reach out and touch the planet, as if it were a globe hanging right at the upper end of the telescope’s tube.

A five inch Clark equatorial: a symbiosis of art and science.

A five inch Clark equatorial: a symbiosis of art and science.

Leslie Peltier’s wonderous 12-inch 15′ 7″ focal length Clark I had the opportunity to use several times came as a gift from Miami University of Ohio in 1959. A vintage 1868 instrument, its objective lens was supposedly figured by Alvan Clark senior himself. When originally finished and just before delivery to Wesleyan University (its first home) it was tested by Professor Winlock of Harvard Observatory in Cambridge, Massachusetts, who declared that it “performed admirably.” Leslie, himself, offered that with the Clark “star clusters like M13 are gorgeous quite beyond belief, together with the Ring Nebula and the faint and difficult hot blue star in the center of the ring.

It is right and proper to endeavor to preserve these instruments for future generations.

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My Zeiss AS80/1200

 By Alexander Kupco, Ricany, Czech Republic

Zeiss AS lenses are one of the legendary objectives made by the company. Having been  designed by Dr. August Sonnenfeld in the first half of 1920’s, these popular lenses were in production until the 1990’s when Zeiss closed its astronomical division. At the speed of f/15, they were meant to replace the longish type A Zeiss apochromats. The AS doublets were based on the short Flint glass KzFS combined in Steinheil configuration with regular crown BK7. The resulting color correction was about 50% better than for the doublets made out of standard flint and crown glasses. In particular, the AS80/1200 lens was classified by Zeiss as semi-apochromatic.
Many of my own countrymen who held a longstanding interest in astronomy had telescopes equipped with AS lenses, as Jena were the only available professional opticians available during communist era. Many people have in their homes small Zeiss lenses, mostly achromats – the  C50 and C63 in particular – eyepieces, and other accessories. Zeiss refractors were the first proper astronomical telescopes that I have looked through as a kid. When I came across a AS80/1200 lens it was the perfect catalyst to trace a memory line to my youth. So I bought one.

Figure 1: The Zeiss AS80 lens in its exquisite cell.

Figure 1: The Zeiss AS80 lens in its exquisite cell.

My Zeiss AS80/1200 lens, Fig. 1, came with a price tag people usually pay for one CZJ 0.965″ orthoscopic eyepiece and it also came with two such eyepieces and a Zeiss revolver head.
While for many, the AS80 represents a luxury item, it is for me the cheapest telescope
that I own. The lens came with simple tube. I equipped it with Zeiss helical focuser, new
baffles, and the telescope was ready to go, Fig. 2.

Figure 2. the newly designed baffles for the AS 80 refractor.

Figure 2. The newly designed baffles for the AS 80 refractor.

I’m using AS80/1200 regularly for more than three years. It became my primary choice
for winter backyard sessions thanks to its ability to cope with large temperature changes.
I keep the lens detached from the tube at home at room temperature. I just put it out on window-sill before going out. In those ten minutes taken by the preparation for the observation, dressing, and mounting the tube, the lens is ready even for critical planetary
observation at high magnifications. In twenty minutes, I can be done with the sketching
Jupiter including seeing the Red Spot Junior. This is not so trivial accomplishment. My former 130mm ED doublet was just starting to show Great Red Spot under similar conditions after about 30 minutes of being outside. I never had a productive winter Jupiter
session with the large doublet due to the notoriously unstable winter weather. Here is a typical deep sky winter session that documents why I treasure the lens. It was the first opportunity to see stars after 15 cloudy nights. It was clear that the cloudless window is very short. I would not bother to set up my larger 250mm Newton in such conditions.I quickly took out AS80 lens and put the tube on my light alt-az mount. The plan was clear, I wanted to hunt for planetary nebula NGC 1360 in Fornax.
During those cloudy days, I came across an idea to create a list of objects discovered by small telescopes. Planetary nebula NGC1360 was one of the interesting objects I have learnt about thanks to this survey. I have never dared to even look at Fornax area before. From my location, a small town just on the border of 1.5 million people city, I usually cannot see by eye even Eridani. This night was special, the transparency between clouds was excellent and I could easily identify the star by eye.This star was a starting point for the hunt. I jumped from there to a nearby system, o2 Eridani. I remembered from two years ago that it had been a nice triple star with white dwarf and one of the smallest known red dwarf stars. At that time, this was an easy object in my 250mm Newton. In 80mm refractor, it was more tricky and it took me some time and untrivial effort to see the third component. A 80mm lens can show isolated 11th magnitude stars without much difficulty, however this red dwarf is placed only 9″ from the 9.5 magnitude white dwarf. No sign of the third component was seen at 171x. There was something at 235x but I had to crank the power up to ridiculous 465x to clearly reveal the presence of the red dwarf. Next object on the way down to Fornax was planetary nebula NGC 1535. I  visited it for the first time, and it was a fine view even in small refractor. I could glimpse its ring structure at 96x and 120x. There was no more time to study it at higher magnifications. It was obvious that the clouds are back very soon.
With next jump, I went directly to NGC 1360. The clouds were already there as the number of visible stars in the eyepiece was changing in time. In moments of good clarity, the nebula started to show itself. At 48x with UHC filter, it was very faint milky cloud elongated in north-south direction. I estimated its size from 8′ to 10′. Then, I checked nearby galaxy NGC 1398 which was also discovered in a small telescope. There was no chance however owing to light pollution as UHC filters are not helping on galaxies too much.
Finally, I quickly turned the scope towards another gap in clouds to open cluster NGC 1662. I had run on it two months ago and I liked it. This evening, I could see the cluster already in the 50mm finder as a hazy star. In AS80, it was very fine group of about 8 brighter stars forming ship with short mast sailing roughly in north-west direction. In between the bright stars, I could glimpse with averted vision another dozen of faint companions.
Fifty minutes ran by quite quickly and the clouds were back. I hope the story documents
why I like my small refractors. They allow me to enjoy even the shortest periods of clear
sky in times when I would not be even thinking of taking out my heavy and long 250mm
Newton.
Another joy with AS80/1200 comes from observing planets and Moon. The superb optics provides breath-taking views. My feeling is that I’m not able to record properly all I can see even on such small target as is Jupiter, so why to bother with setting up something larger. To get a flavour of what this lens is able to deliver, see my sketches in Figs. 3 and 4.

Figure 3: One of Alexander's superb renderings of Jupiter with his AS 80 refractor.

Figure 3: One of Alexander’s superb renderings of Jupiter with his AS 80 refractor.

Of course, f/15 refractor is very suitable tool for splitting tough pairs of stars. Zeiss
AS80/1200 is no exception. Small diameter combined with excellent optics provides text-
book in-focus star images, nice Airy disc surrounded by faint first diffraction ring, quite often. There is no need to wait for nights with exceptional seeing.The lens nicely splits stars above Dawes limit. Due to steady Airy discs I can sometimes glimpse even closer companions. It is fun to notice bumps or smaller discs burried partially in the main disc. Some of the most tough doubles that I was able to detect in AS80 were 2780 (6.1+6.8, 1.0″), tight central pair of Sco (4.4+5.3, 1.3″), or Aql (6.3+6.9, 1.4″).
Thanks to the good optics, tight unequal pairs are no problem for the lens. One of the most extreme example is highly unequal pair Dra (2.8+8.2, 4.8″). It took me five attempts made during one year until I run on favourable conditions and I was able to glimpse the faint companion finally.
With time, I was hooked by the AS80 lens more and more. It made me to want trying
other Zeiss optics. I was lucky enough to find several pieces for very reasonable prices.
Right now, I have another AS80/1200 lens from the WWII era, Fig. 5. The glass is held
in a nice brass cell and the lenses are not coated. My feeling is that the older lens exhibits
even better optics that the lens from GDR time. My main telescope, and my pride, that is mounted in my darker-site observatory, is equipped with lens AS110/1650. When I was buying this lens in beautiful brass cell, I had no idea about its connection to the history of Zeiss AS lenses. The surprise came when the lens was dated by Wolfgang Busch, optician and renowned collector of old Zeiss optics.

Figure 4: A very fine artistic rendition of the Great Nebula in Orion.

Figure 4: A very fine artistic rendition of the Great Nebula in Orion captured with the Zeiss As80.

His estimate, the latter part of 1924, was quite a bit earlier than the year 1926 mentioned in the books for the creation of AS lenses (R. Riekher, Fernrohre und Ihre Meister ). Wolfgang told me that the first AS lenses were made already in 1923 and that my lens is probably the first AS lens made in this diameter. This little touch of history adds a whole new dimension to my observing pleasure.
There are many ways how to enjoy the wonders of the starry heavens. For me, small refractors, like Zeiss AS80/1200, represent a way to enjoy them even under less than perfect conditions or when I’m simply too tired to grapple with something bigger.
………………………………………………………………………………………………………
A Grandfather’s Promise
By Dimitrios Barounis
Athens, Greece

Image courtesy of Dimitrios Barounis

Image courtesy of Dimitrios Barounis

You can read Dimitrios’ story here.

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De Fideli

Tales from the Golden Age: The Life & Work of William Frederick Denning (1848-1931).

William Denning ( 1848-1931) pictured with his With-Browning reflector on its simple altazimuth mount.

William Denning (1848-1931) pictured with his 10-inch With-Browning reflector on its simple alt-azimuth mount.

 

 

 

 

 

 

 

 

 

 

Remember the days of old, consider the years of many generations: ask thy father, and he will shew thee; thy elders, and they will tell thee.
Deuteronomy 32:7

W.F Denning Faciebat

 

Oh Spring! Dear Spring! Thou more must bring

Than birds, or bees, or flowers-

The good old times, the holy prime

Of Easter’s solemn hours:

Prayers offer’d up and anthems sung

Beneath the old church towers.

                                                                                                      W.F Denning

 

The mid to late 19th century was a period of frenetic astronomical activity in Britain. Inspired by the enthusiasm of home grown ‘clerical’ popularisers of astronomy, such as W.R Dawes and T.W Webb, a new generation of amateur astronomers, forming societies across the length and breadth of the country, would take up the gauntlet of observing the heavens in search of booty. Telescopes were becoming more popular, not just the achromatic refractor, which held a special place in the history of Victorian astronomy, but also the Newtonian reflector, which was experiencing a bit of a Renaissance owing to the introduction of silver-on glass mirrors offering decent aperture at prices that suited the budgets of many more amateurs. It was in this renewed spirit of enthusiasm that William F. Denning was to make his mark on the astronomical community.

Little is known of his early life. The eldest son of Lydia and Isaac Denning, William was born on November 25, 1848 in the picturesque village of Redpost, Somerset. Isaac was a retired army officer-turned-accountant, who provided a modest income for his family. When William was seven, the Denning family moved to the city of Bristol, presumably to realise a higher standard of living by entering an accountancy partnership – Denning, Smith & Co – where they prospered, and were further blessed by three more children – a brother Frederick and twin sisters, Margaret and Emma. Not much is known of William’s education, although judging by the standards of his many later astronomical correspondences, it is reasonable to assume that he received a good foundation at school. After leaving formal education, William followed his father into the accountancy business, remaining with the firm until Isaac’s death in 1884. William showed great promise as an athlete, cricketer and even dabbled in hockey. Indeed, according to a later account by T.E.R Philips, Denning was invited by the legendary cricketer, Dr. William G. Grace, to be a wicket keeper for the county of Gloucestershire – a considerable honour in itself – although for reasons that still remain obscure, he declined the offer. One guess is that the young man had other ambitions related to astronomy, which he had expressed an interest in as early as 1865, aged just 17.

One event that may have consolidated his decision to follow an astronomical career was the great Leonid meteor showers that occurred between 1866 and 1868, during which time many spectacular fireballs were witnessed streaming across the mid-November night sky, and having opened a correspondence with Alexander S. Herschel, the son of Sir John Herschel, who had carried out pioneering work on meteor spectroscopy. And while meteor watching was to become the enduring passion of Denning’s later life, his earliest forays into the hobby were decidedly varied. In 1865, Denning bought his first telescope, a good 4.5 inch refractor, with which he would carry out extensive work on the groupings of sunspots, observations of the transit of Mercury in the year 1868, as well as transit timings of the Galilean satellites of Jupiter, the latter of which formed the basis of his first publication, aged just 20, appearing in the Astronomical Register 6, Vol 92, 1868, and auguring his subsequent meteoric rise in the community of British amateur astronomers.

This first publication in the Astronomical Register was immediately followed up by several others in the next few years, during which time Denning was to spear-head a coordinated effort among dozens of his fellow amateurs to observe the Sun for a month-long period between March 14 and April 14 1869, in order to search for the elusive planet Vulcan, which was postulated to exist inside the orbit of Mercury. Although no such planet was ever seen, it did not in any way diminish his enthusiasm for coordinating multi-observer surveys in the future. Indeed, it was this boyish enthusiasm for his work that led to him founding a new society with the help of his more influential astronomical friends. Known as the Observational Astronomical Society (OAS), it was established on July 1 1869, with Denning himself acting as its first treasurer and secretary. Although the OAS did not ultimately have the legs to endure the sweeping changes that occurred over the coming years, ceasing altogether to exist after 1872, many would agree that it was a legitimate foreshadowing of the much more successful British Astronomical Association(BAA), which was founded in 1890, and which is still going strong today.

Intrigued by the growing interest in large aperture silver-on-glass reflectors that were the talk of the town during these years, and sensing ‘the pomp and ceremony’ of refractor culture, Denning used his brain and took a punt on a 10-inch f/7 With-Browning reflector with a simple alt-azimuth mounting, which he purchased in 1871. Being unusually enthusiastic about exploring the telescope’s potential under the starry heavens, the truth soon set him free, and he embraced the same instrument to embark on an extraordinary program of visual work on the bright planets. It was these observations, and his subsequent commentaries, that were to abruptly hurl the young man into the limelight of the international astronomical community.

Reference

Over the next 15 years or so, Denning became universally acknowledged as one of the finest planetary observers of his age, and especially of Jupiter. Having access to the best astronomical literature of the day, he became acutely aware that the drawings made by astronomers using larger telescopes were not revealing as much detail as one might have anticipated from their superior aperture. As a case in point, he argued that the Jovian whole disk drawings carried out by the Third Earl of Rosse using the 72 inch Leviathan of Parsonstown were no more detailed than backyard telescopes with very modest apertures in comparison. In addition, being intimately familiar with the work of other great observers of his era, such as the English solicitor and amateur astronomer, Stanley Williams, who had used a 6.5 inch Calver reflector on a simple equatorial mount to make all of his highly detailed drawings of the Giant Planet, Denning reached this remarkable conclusion in a publication communicated in 1885:

Many people would consider that in any crucial tests the smaller instrument would be utterly snuffed out: but such an idea is entirely erroneous. What the minor telescope lacks in point of light it gains in definition. When the seeing is good in a large aperture, it is superlative in a small one. When unusually high powers can be employed on the former, far higher ones proportionally can be used with the latter. We naturally expect that very fine telescopes, upon which so much labour and expense have been lavished, should reveal far more detail than in moderate apertures, but when we come to analyze the results it is obvious such an anticipation is far from being realized. The glare of excessive light and the endless mouldings and flaring of the image can only have one effect in obliterating delicate markings.

Reference

Denning’s comments were made in response to some criticisms of both his work and the observations made by other keen observers he enjoyed correspondences with, who seemed to confirm rapid atmospheric changes in Jupiter’s massive turbulent atmosphere. In particular, they were directed at the comments made by the professional American astronomer, G.W. Hough, who employed the 18.5 inch Dearborn refractor in his own Jovian studies, but who had failed to notice the same changes. Consequently, Hough dismissed the reports of Denning et al as being attributed to “the poor quality of the images” in the smaller telescopes. Rising to Hough’s criticism, Denning not only reaffirmed what he and others had seen but began to seriously wonder why Hough had missed seeing these changes with such a formidable telescope. In another 1885 publication, Denning writes:

Apertures of 6 to 8 inches seem able to compete with the most powerful instruments ever constructed……a very large aperture shows the rushing of vapours across the disc, and violent contortions of the image, which are the inevitable result.

Reference

In support of his conclusions, Denning pointed out that the disk drawings of Mars made by Asaph Hall and the Scots-born American astronomer, William Harkness,  were noticeably ‘bland’ in comparison with those drawn by the Reverend Dawes and Giovanni Schiaparelli, who both used instruments of 8-inch aperture, as well as the fine work of the British artist, Nathaniel Green, who had conducted extensive Martian observations from the Madeira archipelago, off the coast of Morocco, using a 13-inch silver-on-glass reflector.

Reference:  Sheehan, W, Planets and Perception, University of Arizona Press, (1988), pp 103.

In addition, Denning also brought Sir William Herschel’s opinions in these matters to the fore:

Sir William Herschel seems to have the non-utility of large instruments in the observation of bright planets for he wrote as follows: “On the course of these observations[on the belts of Saturn] I made ten new object specula and fourteen small plain ones for my 7 foot [6.3 inches] having found that with these instruments I had light sufficient to see the belts of Saturn well and that here [Bath, England] the maximum of distinctness might be much easier obtained than where large apertures were concerned.

After Nathaniel Green acquired his ‘ultimate’ telescope back in England – a reflector of 18 inches aperture – he found it useful to fit it with a “convenient gradation of stops.”

This was just the ammunition Denning needed to drive home his own findings:

If a large diameter telescope is useless without stops, wherein does its utility consist? Better at once to adopt a smaller speculum and obviate the more troublesome manipulation of a large instrument. True there are very rare occasions when all the aperture may be utilized; but are they worth waiting for, and when they come, do the results answer expectations?

Reference

Denning undoubtedly had a point, as the air cells coursing over the British Isles do indeed seem to favour moderate but not large apertures, but it was not true everywhere. For example, in a study conducted by the American astronomer, Charles A. Young, using the 23-inch Clark refractor at Princeton, New Jersey, he admitted that while small apertures are less sensitive to the vagaries of the Earth’s atmosphere, in his opinion, the images through the 23-inch were generally far superior to those garnered by the 9-inch glass with a frequency of about one night in three.

Notwithstanding these comments, Denning was no Luddite, acknowledging that for other avenues of astronomical observing, aperture was an indispensable commodity:

In certain departments of research large apertures are absolutely required, and have performed work utterly beyond the capacity of moderate instruments.

Reference

Denning’s keeness for observing was legendary, so much so that it is no wonder he did so well with such a modest telescope without a driven mount, and no cooling fans; a circumstance that flies in the face of the modern amateur, who often regard such devices as ‘essential.’ Denning’s reports are also entirely in keeping with the author’s own field experience with a modern 8-inch f/6 Newtonian, which has proven to be his best and most used telescope (also un-driven and with no cooling fans).

We may gain a glimpse of Denning’s extensive experience by taking a look at a few comments he made in Chapter VIII of Hutchinson’s Splendour of the Heavens:

The telescope’s definition of Jupiter varies greatly according to the altitude of the planet. From 487 nights of observation (ten inch reflector) at Bristol the following percentages were observed:-

% Nights                                 Very Good         Good        Fair         Bad       Very Bad
Jupiter South of Equator            7.0                 14.1         15.5         33.8           29.6
Jupiter North of Equator           19.8                 29.1         25.6         18.6             7.0

The reader will note the great advantage of observing the planet higher in the sky as viewed north of the celestial equator, where the orb is less affected by atmospheric turbulence. Note also the percentage of useful nights and/or observing spells Denning enjoyed from Bristol; a number wholly inconsistent with the ‘perpetual bad weather myth’ promulgated by modern amateurs. Self evidently, there were more clear nights where work could be done over ‘cloudy’ England than is commonly reported today.

Reference: Philips, T.E.R (ed.), Hutchinson’s Splendour of the Heavens, Vol 1, Hutchinson & Co, (1923), pp 337.

Intriguingly, this anomalously high frequency of good observing nights/spells communicated by Denning was also independently reported by the consummate British amateur, Charles Grover, who’s biographer revealed that he observed on 146 nights (40 per cent) during the year 1886.

Denning was a keen observer of Jupiter’s Great Red Spot (GRS), watching it change in colour, shape and size over many years with his 10-inch With-Browning speculum, and about which he discusses at great length in Splendour of the Heavens. On the evening of February 13 1888, he made a sketch of the Giant Planet with his alt-azimuth reflector, which shows a considerable amount of detail.

Denning's sketch of Jupiter dated February 13, 1888 showing the unusually large GRS and bright cloud within its confines. Source: http://www.phenomena.org.uk/page105/page131/page131.html

Denning’s sketch of Jupiter, dated February 1888, made with his 10-inch Calver reflector, showing the unusually large GRS and bright cloud within its confines.
Source: http://www.phenomena.org.uk/page105/page131/page131.html

The size of the GRS is relatively enormous though, much larger in comparison to anything seen in recent years. The reader will note a large bright cloud-like structure encapsulated within the spot. Out of curiosity, this author examined another Jupiter drawing by the young E.E. Barnard using a fine 5-inch f/15 Byrne refractor, made as close in time as possible to Denning’s sketch. As this link shows (bottom right sketch) dated April 22, 1886, Barnard’s superb eyesight recorded an equally large GRS with the same cloud like structure inside it, and with an accompanying note (seen on the previous page) which states:

A white cloud has formed over the middle of the Great Red Spot, almost obliterating it.

Could Denning and Barnard have observed the same feature, albeit a couple of years apart? I dare say, it’s very probable!

Do you have the historical evidence to dismiss this possibility out of hand? I’d be happy to  weigh the evidence.

Comparing the detail of the two sketches, we see the superior resolving power and contrast transfer of Denning’s reflector coming into play, don’t you think?

Denning’s contribution to planetary astronomy extended well beyond Jupiter though. For example, in 1876, Professor Asaph Hall using the great 26-inch refractor at the U.S. Naval Observatory, recorded an equatorial spot on Saturn, which he followed and measured through 60 rotations, and from these data deduced its period to be 10 hours, 14 minutes and 24 seconds. Hall was careful to stress that this may not have been the rotation period of the planet per se, only that of the spot itself. Back in England, both Denning and Stanley Williams, using far more modest 10 inch and 6.5 inch specula, respectively, were following vague markings on the Saturnian globe and came to a rotation period just two seconds shy of Hall’s estimate, all of which are in agreement with the best modern values for the planet’s rotation.

Reference: Clerk, A., A Popular History of Astronomy During the Nineteenth Century, Cornell University Press, 2009, pp 167

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An Aside: Quality Never Goes Out Of Fashion

How good were With and Calver mirrors?  In a word, ‘excellent’, by all accounts. Calver deliberately left his mirrors slightly undercorrected to compensate for the natural overcorrection a mirror would exhibit as it cooled off. This is also the case with the majority of modern, mass produced mirrors. A few years back, I had the pleasure of conversing with London-based amateur astronomer, Robert Katz, who lovingly restored a magnificent 10-inch f/8 Calver reflector on a simple alt-azimuth mount. He was kind enough to share his experiences of the telescope with me.

My f8 10″ Calver looks like an unwieldy beast and by any modern standards is overwhelmingly long. The original wooden stand had rotted and was missing its slow motion controls when I found it, but luckily Len Clucas, the former professional telescope-maker for Grubb Parsons in Newcastle had inherited an identical stand and cradle from the late master mirror maker David Sinden which he refurbished for me. A stepladder is essential for objects over 30 degrees high and viewing near the zenith is positively dangerous. And yet – climbing up to the eyepiece apart – it is remarkably easy to use. The eyepiece is always in a convenient position – assuming you can reach it – the azimuth and altitude controls are smooth and make tracking easy even at powers of 300x and the ingenious system of a clamped tangent arm makes rewinding the azimuth screw simple without losing position. Even though it weighs a ton the telescope is also beautifully balanced; unclamped from the slow motions, with a 40mm eyepiece in the barrel, I imagine it is the closest you can get to the laid-back star-hopping Dobsonian experience with Victorian equipment.

The optics are fine and because the focal length is actually less than that of a standard SCT, views of deep sky objects are impressive with a low power eyepiece. It comes into its own with the planets, though, and the exceptional opposition night of Jupiter in September 2010 was memorable in many ways. Thanks to good seeing in South West London – the telescope is in Hampton Hill – I spent most of the night watching Jupiter turn in exquisite detail using a fine telescope made in 1882 by one of the two great telescope makers of his day; but a telescope so simple that a child can learn to operate it confidently in five minutes. 

A lovingly refurbished 10" Calver reflector. Image credit: Robert Katz

A lovingly refurbished 10″ Calver reflector. Image credit: Robert Katz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thus, by all accounts, these fine Newtonian telescopes were first rate tools that enabled their owners to conduct detailed studies of the firmament. The fact that Denning and others used an alt-azimuth mounting to conduct his planetary studies  (most of which was published in the best astronomical journals of the day)  is also to be noted. Today, there is a tendency among some amateurs to dismiss the use of an undriven alt-azimuth mount because it doesn’t keep the planet in the centre of the field. Truth be told though, there will be plenty of opportunities (his was a f/7ish remember?) when the finest details of a planet’s aspect can be made out as it crosses the field of view, as this author has discovered over several years of continued work with simple, undriven mounts. So, like everything else in life, intrepid folk always find a way ’round such technical ‘obstacles’.

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In parallel to his growing interest in planetary observing, Denning took up the activity of comet hunting sometime in the 1870s, and he was rewarded  for his efforts in the predawn hours of October 4 1881, when, shortly after a spell observing Jupiter, he inserted a low power eyepiece and began sweeping the sky in its vicinity. Almost immediately he caught sight of a ‘suspicious’ object that turned out to be a new short period comet. Nearly another decade elapsed before discovering his next icy interloper, which he stumbled upon in 1891 and this was followed by two other comet discoveries in 1892 and 1894. For each of these discoveries, Denning was awarded the Bronze Medal by the Astronomical Society of the Pacific. Denning was also the co-discoverer of a comet with the famous Americcan astronomer, E.E. Barnard in 1891.

His publication rate rising to some 20 articles per year, Denning’s reputation as an observer of repute grew steadily, so much so that he was elected President of Liverpool Astronomical Society for the year 1887, increasing its already large membership from 440 to 641.

In addition to his published articles, Denning embarked upon writing books on amateur astronomy. While his earliest forays into this brave new world was met with unnecessarily harsh criticisms from the priggish founding editor of Nature, Sir Norman Lockyer, his later books, including, Telescopic Work for Starlight Evenings (1891), were enthusiastically endorsed by the powers that be.

Many more accolades were bestowed upon F.W. Denning in the closing decade of the 19th century, not only at home but abroad also. The Valz Price of 1895 was awarded to him by the French Academie des Science, and in 1898 Denning received the prestigious Gold Medal of the Royal Astronomical Society in recognition of his monumental work on meteors. He was even given a mention in chapter 2 of H.G. Wells’ famous novel: The War of the Worlds, which was first serialised in 1897.

While it is undoubtedly true that Denning  expressed an interest in the Martian canal theory, he was not convinced of their reality stating that, ” they were far more highly suggestive of natural than artificial production.

Reference

It is not known exactly when Denning acquired his largest telescope, a 12.5 inch Calver reflector, but what is certain is that he never acquired equatorial mounts for any of them. Nor did he bother building an observatory for his telescopes; a custom quite out of sink with the prevailing culture of his day. His voluminous drawings of all the major planets are not striking for their artistic renderings but they do reveal the workings of a true telescopic draughtsman, where accuracy and objective truth were held in higher esteem than artistic license.

By the end of the 19th century, W.F.Denning was one of the most famous astronomers in the world, commanding an extraordinary web of correspondence with the scientific giants of his age. And while the accolades kept piling up, Denning’s reaction to this new-found fame was not in keeping with a man of his standing. An admixture of declining health and bitter criticism over his ideas regarding the stationary nature of meteor radiants, conspired to alienate the consummate English amateur so much so that he eschewed the limelight and became increasingly reclusive, giving up telescopic astronomy altogether by 1906.

It is not known how Denning made a living in the last few decades of his life, but it is known that he did receive a Civil List Pension by the British Government beginning in 1904, when he was 56 years old. This amounted to an annual stipend of £150, “ in consideration of his services to the Science of Astronomy, whereby his health has become seriously impaired and of his straitened circumstances.” And while there is no evidence that he earned an income from the family accountancy business, it has been suggested that he received  sporadic payments for his literary works, and some occasional prize money for his discoveries that just barely kept the wolf away from the door.

Reference

Though he lived a solitary life, Denning kept up communication with the outside world through his many letters of correspondence and scientific publications. And while his telescopic career was now far behind him, it was by no means the end of his discovery days. In a singular period between 1918 and 1920, Denning, now a septuagenarian, observed a nova in Aquila (V603 Aql), the discovery of which was later contested. However, during a routine meteor watch in August 1920, the 72 year-old Denning discovered a new star in Cygnus, shining with a magnitude of 3.5.  Nova Cygni was the talk of the astronomical world for many months to come and he enjoyed a surge in correspondences from an adoring international following.

Reference

As well as his correspondences, Denning took to writing poetry, in which he often explored the themes of Nature, her cycles of decline and renewal. It has been suggested that he was a Christian.

The last decade of Denning’s life is one of great sadness. Upon visiting him at his last known address at Eggerton Road, Bristol, in 1922, Dr. W.H. Steavenson recalled meeting a wretched soul, living in abject poverty, and with only an open fire and a tobacco pipe as sources of comfort. Even when Denning left the house, he became the butt of every schoolboy’s joke, who ignorantly taunted the eccentric astronomer .

Denning remained an active observer of the heavens right up until a few weeks before his death, aged 83, caused by heart disease, on June 9th 1931. Entirely self taught, and arguably the most active and gifted observer of his generation, he will be remembered for his unbridled enthusiasm for his science, his love of nature and for his encouragement of a new generation of stargazers across the world. W.F.Denning (1848-1931); an extraordinary life lived.

De Fideli

Planetary Telescopes.

The author's plnetary telescope; a 8 inch f/6 Newtonian reffector.

The author’s planetary telescope; a 8 inch f/6 Newtonian Reflector.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

But thou shalt have a perfect and just weight, a perfect and just measure shalt thou have:

Deuteronomy 25:15

Comments on planetary telescopes by established authorities** in the field over the last 130 years.

As a really efficient tool for systematic work on planets, telescopes of about 8 inch aperture cannot be surpassed. It is useless waiting for the two or three serene nights in a year when the whole diameter of a big instrument is available to really good effect. Amateurs urgently require the appliances most efficient under ordinary conditions and they will find a larger aperture of little avail until it is much reduced by a system of gagging and robbed of that very advantage which is extolled so much; namely grasp of light. The 18.5 inch equatorial of the Dearborn Observatory cost £3700, the great Washington refractor £9000, the great Melbourne Cassegrainean (reflector) of 4 feet aperture cost £14,600, and at first it would appear preposterous that a good 8.5 inch With or Calver mirror, that can be purchased for some £30 will effectively rival these expensive and elaborate instruments. Many people would consider that in any crucial tests the smaller instrument would be utterly snuffed out: but such an idea is entirely erroneous. What the minor telescope lacks in point of light it gains in definition. When the seeing is good in a large aperture, it is superlative in a small one. When unusually high powers can be employed on the former, far higher ones proportionally can be used with the latter. We naturally expect that very fine telescopes, upon which so much labour and expense have been lavished, should reveal far more detail than in moderate apertures, but when we come to analyze the results it is obvious such an anticipation is far from being realized.

From W.F. Denning’s, The Defining Powers of Telescopes, Anno Domini 1885.

The planet looks as if cut out of paper and pasted on [the] background of sky. It is perfectly hard and sharp with no softening of edges. The outline and general definition are much superior to that of a refracting telescope.

E.E. Barnard comparing the views of Saturn seen with the newly erected 60-inch reflector atop Mount Wilson, with the 36-inch Lick Refractor, Anno Domini 1908

Source: Sheehan, W. The Immortal Fire Within: The Life and Work of Edward Emerson Barnard, Cambridge University Press, pp 398. Anno Domini 2007.

Although something worth recording may be seen even with a 3-inch, the intending student of Jupiter should have available a telescope of not less than 6 inches aperture. With such an instrument a great deal of first-class systematic work can be accomplished and only the smallest of the really important markings will be beyond its reach; indeed, until only a year or two before his death Stanley Williams made all his invaluable observations with a 6-inch reflector. An 8-inch is probably adequate for all purposes; a 12-inch certainly is. The bulk of the author’s work has been done with a 12-inch reflector; and although it would not be true to say that he has never yearned for something larger when definition was superb, the gain would have been mainly aesthetic and he has never felt that anything important was being missed owing to the inadequacy of his equipment.

Peek, B.M., The Planet Jupiter:The Observer’s Handbook, Faber, pp 36-37, Anno Domini 1981.

If the aperture exceeds about 12 inches , the atmosphere will seldom allow the full aperture to be used……..Direct comparisons of performance on different occasions have revealed an 8-in refractor showing more than a 36-in reflector; an 11-in refractor surpassing a 12-in reflector; canali invisible in the Greenwich 28-in stopped down to 20 ins, but visible in an 8-inch by T.E.R. Philips; apertures less than 20 ins showing more than the Yerkes 40-in stopped to 30 ins.

From Mars by J.B Sidgwick, Observational Astronomy for Amateurs, (pp 118) Anno Domini 1971.

One of the greatest Jupiter observers, Stanley Williams, used only a 6-inch reflector, but most serious students of the planet now would look for at least an 8-inch, although a good 5-inch OG can reveal surprising detail. This is not the place to debate the relative performance of refractors and reflectors, but good resolution, high contrast and faithful colour rendition are essential. A good long focal ratio Newtonian , a Maksutov, or an apochromatic refractor is probably the best but, as in every field, the quality of the observer is the most important factor, and good results can be obtained with any reasonable instrument.

Moseley T., from the chapter on Jupiter in The Observational Amateur Astronomer, (Moore, P. ed), Springer, pp95, Anno Domini 1995.

To recapitulate: Mars is not an easy target. Because the disc is generally small, it is essential to use a fairly high power telescope if it is hoped to see anything except for the most prominent features. Of course a small telescope such as a 7.6cm refractor or a 15cm reflector will show something under good conditions, but for more detailed work a larger aperture is needed. A 20cm telescope is about the minimum for a reflector; I would not personally be happy with anything below 20cm, though opinions differ, and no doubt observers more keen sighted than I am will disagree.

Moore, P., from the chapter on Mars in The Observational Amateur Astronomer, (Moore, P. ed), Springer, pp78, Anno Domini 1995.

A 3-inch refractor with a magnification of around 50x will show the planet and its ring system, but an aperture of no less than 6-inches is needed for observations to be of value; ideally one should aim for an aperture of at least this size – the larger the better. It has been claimed that the best magnification for planetary observation is about equal to the diameter of the object glass or mirror in millimetres. To see the fine details of Saturn’s belts and ring structure, a magnification of 150x to 300x is necessary, and therefore, according to the above rule, telescopes of 150mm or more are clearly required.

Heath, A.W., from a chapter on Saturn in:The Observational Amateur Astronomer, (Moore, P. ed), Springer, pp113, Anno Domini 1995.

Seeing varies from 0.5 arc seconds on an excellent night at a world class observatory site to 10 arc seconds on the worst nights. On nights of poor visibility, it’s hardly worth observing the Moon with anything but the lowest powers, since turbulence in the Earth’s atmosphere will make the lunar surface appear to roll and shimmer, rendering any fine detail impossible to discern. For most of us, viewing rarely allows us to resolve lunar detail finer than 1 arc second, regardless of the size of the telescope used, and more often than not a 150mm telescope will show as much detail as a 300mm telescope, which has a light gathering area 4 times as great. It is only on nights of really good visibility that the benefits of the resolving power of large telescopes can be experienced. Unfortunately, such conditions occur all to infrequently for most amateur astronomers.

Grego, P., The Moon and How to Observe It, Springer, pp244, Anno Domini 2005.

As a choice for planetary observations then, there is a lot to be said for the Newtonian reflector in the 6- to 10-inch aperture range.

F.W. Price, The Planet Observer’s Guide (2nd Edition), Cambridge University Press, pp 41. Anno Domini 2000

 

It allowed visual scrutiny with very high magnifications, each time it was necessary.

Adouin Dollfus (2002) in a comment pertaining to the efficacy of the Great Meudon Refractor.

A high quality Newtonian reflector is a very powerful instrument, fully capable of superb performance in viewing the planets, when the optics are kept clean and properly aligned. They have been among the favorite instruments of serious planetary observers for many decades.

Bengton, J.L., Saturn and How to Observe It, Springer, pp57, Anno Domini 2005.

As good as my 6-inch f/9 is, the 8-inch f/6 I built soon after is crushingly superior in virtually every way — including planetary performance. This is something to keep in mind if you’re considering a long-focus Newtonian. A long f-ratio helps, but aperture is much more important. Would an 8-inch f/9 be better than my f/6? Probably. But mounting and using a scope with a tube more than 6 feet long is would be a challenge. And when the aperture gets much bigger, it’s easy to keep the secondary size small without resorting to extremely long focal lengths.

From an article entitled,The Big Red One, Sky&Telescope Associate Editor and veteran ATMer, Gary Seronik, commenting on the superiority of a 8-inch f/6 reflector over an optically superlative 6-inch f/9 reflector ‘Planet Killer,’ Anno Domini 2009.

I was once loaned a 4.5 inch refractor by the British Astronomical Association back in the 1990s; it was an excellent instrument, but the optical tube was longer than me! These days refractors come with much shorter tubes, but at considerable cost and apertures of 5 in., or more, however the cost of smaller refractors have come down in recent years. Although they look splendid, remember it is aperture(size of the telescope) that is the most important. Ideally you should get the largest telescope you can for your money.

Abel, P.G, Visual Lunar and Planetary Astronomy, Springer, pp 13, Anno Domini 2013.

All in all, if you can afford it, and if you have the room to house it in some sort of observatory, I would say go for a Newtonian reflector of 10 inches -14 inches aperture and as large a focal ratio as you can reasonably accommodate…..My second choice would be a 5 inch refractor…..having a focal ratio of f/12……or an ED apochromat ( f/8).

North, G., Observing the Moon, Cambridge University Press, pp 52, Anno Domini 2014

When Mars was closest to the Earth in August 2003, the Macclesfield Astronomical Society held a star party at Jodrell Bank Observatory with quite a number of telescopes set up to observe it. As the evening progressed a consensus arose that two scopes were giving particularly good images; my FS102 4-inch Takahashi Fluorite refractor (at around £3500, or $5000, with its mount) and an 8-inch Newtonian on a simple Dobsonian mount newly bought for just £200($300). I personally preferred the view through the f/6 Newtonian but others thought that the FS102 gave a slightly better image, so we will call it a draw. It is worth discussing why these performed so well and, just as importantly, why perhaps the others did not.

From A Prologue of Two Scopes: Morison, I. An Amateur’s Guide to Observing and Imaging the Heavens, Cambridge University Press, xiii, Anno Domini 2014.

** The author chose these individuals based on both published and unpublished observations of planets available from historical archives and/or books, and having (ostensibly) sustained these observations over many years.

                                   Relevant Physical Principles

 

Resolution:

A telescope of diameter D cuts off a wavefront and blurs a point source to an image size, I,  given by I = lambda/D (radians). This can be converted to arc seconds by multiplying this result by 206265 giving I = (lambda x 206265)”/D.

Making both units of diameter and wavelength (arbitrarily set to 5.50 x 10^-9 m)  the same we obtain:

I = 0.116/D

This is similar to the more familiar Dawes formula (expressed in inches given by 4.56/D)

Thus resolution scales linearly with aperture e.g. a telescope with a diameter of 20cm will have an angular resolution twice that of a 10cm instrument.

Contrast Transfer:

Optical engineer, William Zmek, in the July 1993 issue of Sky&Telescope magazine, analysed the effects of a central obstruction on contrast transfer, arriving at this simple rule:

Contrast Transfer of an Obstructed Telescope = Full Aperture – Aperture of Obstruction.

Consider this author’s chosen planetary telescope, a 203 mm Newtonian with a secondary minor axis of 44mm (22% linearly), the resulting contrast transfer will be the equivalent of a 203-44 = 159mm unobstructed aperture, the effects of the spider vanes being essentially negligible (~1-2 %).

This result has been amply borne out by the author’s extensive field testing.See here for details.

Larger apertures also allow the observer to enjoy a larger exit pupil, which is of paramount importance in studying low contrast details at magnifications typically employed in planetary studies. See this link to see how a consideration of the size of the exit pupil can radically change the direction of a discussion about two very different telescopes.

Light Gathering Power:

Image brightness is proportional to the number of photons collected, which in turn scales as the area of the optical surface. Thus a 20cm telescope collects four times more light than a 10cm, all other things being equal. Refractors, having no central obstruction and multi-coatings applied to the glass surfaces have the greater light transmission. Reflective surfaces exhibit proportionally less transmission to the eye due to less efficient reflection off optical surfaces. In the same article highlighted above, the author described the acquisition of ultra-high reflective coatings (and greatly reduced light scatter) to both mirrors (97 per cent). Thus the overall transmission is (0.97)^2 =0.94 and subtracting the obstructing area of the secondary reduces the overall light gathering power to ~0.9. Compared with an almost perfectly light transmitting refractor object glass, this represents a 10% reduction in light, a value that even a seasoned observer would be hard pressed to see. Thus, the author’s 20cm Newtonian has a broadly equivalent light transmission to an unobstructed refractor of equal aperture.

Atmospheric Turbulence, Seeing Error & Viewing Altitude

The astronomical seeing conditions at a given site can be well described by the so-called Fried parameter r0. We need not wade into the mathematical details to understand the basic ideas behind this model. In this scheme of events the air consists of moving cells which form due to small-scale fluctuations in both the density and temperature above the observer, resulting in the blurring and/or moving of the image. The larger these cells are (which is a measure of r0) the greater the aperture that can be profitably employed. For telescopes with diameters smaller than r0, the resolution is determined primarily by the size of the Airy pattern (which scales as 1/D) and thus is inversely proportional to the telescope diameter. For telescopes with diameters larger than r0, the image resolution appears to be determined primarily by a quantity known as seeing error and scales as (D)^5/6. So, for example, a doubling of aperture results in a 1.78x i.e. (2D)^5/6 increase in seeing error. Interestingly, while the seeing error does scale with aperture, the rate of increase is not nearly as rapid as one might anticipate. This implies that large apertures can work at or near optimally, though maybe not as frequently as smaller apertures.

Reference here.

The best estimates of r0 for typical observing sites used by the amateur astronomers seems to be in the range of 5–20cm (2-8 inches) and generally larger in the better sites at high altitude, where bigger telescopes are pressed into service. Intriguingly, r0 also appears to scale somewhat with wavelength, being as high as 40cm at 900nm(near infrared).

Reference here.

Seeing is also dependent on the altitude of the planet owing to the variation in air mass through which it is viewed. If one observes a planet at the zenith, one looks through 1 air mass. At 30 degrees altitude, the air mass through which the observer views is fully doubled and at 10 degrees altitude it shoots up to 5.6 air masses!

Reference: Morison, I., An Amateur’s Guide to Observing and Imaging the Heavens, Cambridge University Press (2014), pp 22.

In general, a long-held tradition recommends waiting for the planet to rise above 30 degrees altitude to begin to exploit the potential of any given telescope, large or small.

Taken together, these physical parameters can be used to adequately explain all of the aforementioned comments made by celebrated planetary observers over the decades and centuries.

Discussion:

Unbiased testimonies provide a bedrock upon which sound conclusions can be formulated. It is self evident that aperture plays a crucial role in seeing fine detail and it is reassuring that basic optical principles reaffirm this.

The list of British observers quoted above; Denning, North, Moore, Abel, Grego, Heath and Sidgwick etc, highlight the efficacy of moderate but not large apertures in divining fine detail on planets. The consensus appears to be that apertures of between 6 and 10 inches are most efficacious in this regard. This may be explained in terms of the size of the atmospheric cells that move over British skies, which allow telescopes in this aperture range to be exploited. My own discussions with many experienced planetary observers abiding in Britain affirm the truth of this; British skies seem to favour these moderate apertures. It is important to note that this conclusion has little to do with planetary imaging, which often employs significantly larger apertures to excellent effect.

The testimony of Gary Seronik shows that an optimised 6-inch f/9 Newtonian – which presumably would provide views rivaling a 6-inch apochromatic refractor, was comfortably outperfomed by an 8-inch f/6 Newtonian, again confirming the superiority of a little more aperture.

The testimony of E.E Barnard at Mount Wilson and Adouin Dollfus at Meudon shows that larger apertures can be used to much greater effect if seeing conditions allow. Both Meudon and Mount Wilson have enabled telescopes of 30 and 60-inches to be used visually, indicating that the atmosphere can be particularly good there and for long enough periods to permit a meaningful program of visual study.

There evidently exists regions on Earth where the seeing is poor (small r0) for prolonged periods of time, explaining why amateurs in these regions stick to smaller apertures. This in part explains the popularity of small refractor culture.

The most intriguing testimony is offered by Professor Ian Morison, also based in the UK, which, on the face of it, seems to lend more credence to small refractor culture. The reader will recall that during the August 2003 Martian opposition, a large number of amateurs, fielding various telescopes, were present at Macclesfield, England. Morison claimed that two telescopes were doing particularly well; a Takahashi FS102 Fluorite refractor and a mass produced 8″ f/6 Dobsonian and that there was no clear consensus on which was delivering the better views. Having owned several econo- and premium 4 inch apochromatic refractors (and even a gorgeous 4-inch f15 classical refractor), this author (also based in the UK) has become intimately familiar with their performance. And while they all provided good views of the planets, they come nowhere near the performance of the author’s 8-inch f/6 Newtonian, which, despite its very modest cost, proved ‘crushingly’ superior to the former.

So, Morison’s testimony presents an apparent contradiction, which must have a rational explanation.

Further investigation revealed that during the August 2003 Martian opposition, the maximum altitude of the Red Planet was just 23 degrees at meridian passage as observed from London (51 degrees North latitude).

Reference here

Since Macclesfield (53 degrees North latitude) is further north than London, the maximum altitude of Mars would only have been 21 degrees and thus was significantly below the minimum altitude recommended – 30 degrees – for planetary study. Thus, it is not at all surprising that Morison et al reached the conclusions they did.The Newtonian being more sensitive to the vagaries of the atmosphere would not have been performing optimally at that low altitude, while the smaller refractor was performing much as it always does. In addition, this author observed Mars during the same August 2003 opposition using a 20cm f/10 Schmidt Cassegrain. At 56 degrees North, the planet was only 18 degrees above the horizon at meridian passage. Needless to say, the images of Mars were nothing to write home about.

Interestingly, this author reached the same conclusion whilst comparing visual drawings of Jupiter conducted with a Celestron 8″ f/6 Dobsonian during the mid-1990s with those delivered by a 5-inch refractor in much more recent apparitions. It was subsequently discovered that Jupiter was low in the sky in Aquarius at this time, while the 5-inch refractor enjoyed views of the Giant Planet situated much higher in the sky. Last year’s Jovian apparition revealed the clear superiority of the 8-inch f/6 Newtonian over the 5-inch under these more favourable conditions.

Thus there is no contradiction; aperture rules when conditions are reasonable to good. Anomalies only arise under sub-optimal conditions – persistent bad seeing, low altitude viewing etc – or if one telescope has not fully acclimated when the other has etc, hardly a fair test.

This author has brought the reader’s attention to the efficacy of a modified 8-inch Newtonian on all types of objects; deep sky, planets, lunar and double stars. These testimonies provide further evidence that such an aperture – 20cm – is probably optimal for British skies and many other environs besides.

De Fideli

Tales from the Golden Age: Thomas Harriot; England’s First Telescopist.

Thomas Harriot ( 1560-1621); England's first telesopic astronomer.

Thomas Harriot ( 1560-1621); England’s first telesopic astronomer.

 

 

 

 

 

 

 

 

 

 

 

 

What is remarkable and possibly says much about Harriot’s personality, is that he expressed only admiration for Galileo without the slightest trace of jealousy.
Dr. Allan Chapman.

The mid-16th century was a period of tumultuous change in Europe; the Protestant Reformation having swept across the kingdoms of the north, whilst in southern Europe, Roman Catholicism still held sway. The bulwark of the Renaissance had introduced radical new ideas in science, architecture, politics, art and literature, inspired by a palpable sense of nostalgia for the triumphs of classical antiquity. Knowledge, for so long the preserve of the rich and powerful, was now being disseminated at a hitherto unprecedented rate to the proletariat. The printing press had empowered a new generation of scholars with the fruits of human knowledge, not just in Latin, but in the mother tongues of the various kingdoms, principalities and nation states of a new and self-confident Europe.

This was the world that Thomas Harriot was thrust into, born sometime in the year 1560, in the county of Oxfordshire, England. Though he likely had a sister, his ancestry remains somewhat of a mystery to modern historians, and the first we hear of Harriot comes from his matriculation to St. Mary’s Hall, a daughter house of Oriel College, at the University of Oxford, on December 20, 1577. In order to matriculate, Harriot would have had to demonstrate a mastery of classical Latin and Greek, both spoken and written, as well as the Bible, the pillars of knowledge upon which all prospective Tudor scholars were encouraged to embrace. We can infer from this that Harriot’s family placed great value in education for its own sake and that they had sufficient wealth to prepare the youth for such a career, a circumstance that the majority of children could not yet enjoy.

At St. Mary’s College, Harriot would have been absorbed in what we might call a ‘classical’ education, with its strict adherence to Latinity, supplemented by rhetoric and argument, the elements of Protestant theology and civil law. Any graduate worth his salt would be expected to present and debate complex ideas in order to excel in the three principal career options open to him; jurisprudence, the Church and Parliament. This education would also include a thorough grounding in mathematics, geometry and Ptolemaic cosmology. It was in these latter studies that Thomas Harriot would excel.

It was most likely here also that Harriot first came to the attention of Walter Ralegh (1552-1618), eight years his senior, and himself a graduate of Oriel College. By his late twenties, Ralegh had established a great name for himself, both at home and overseas, as a naval commander, scholar and showman, having the ear of the Virgin Queen herself. By this time, England had become a formidable maritime power with an imperious outlook, and Ralegh had set his sights on the colonisation of the eastern Atlantic seaboard of North America. To make this a reality though, Ralegh was always on the lookout for young and enterprising officers with a mathematical penchant, to conduct the surveys, the proper execution of various censuses, as well as the creation of maps of these new territories. It was in this capacity that Harriot entered the employ of Ralegh, who bequeathed him an opulent apartment annexed to his own mansion at Durham House, on the banks of the River Thames.

Harriot’s first mission was to accompany Sir Richard Greenville, himself under the auspices of Ralegh, to Virginia, on board the Tiger, which set sail in the Spring of 1585. His duties were to thoroughly survey the hinterland of the small, Christian settlements that had sprung up around the territory of Roanoke, to learn the language and customs of the native Americans and, if possible, to purchase land from them. This was not to be a bloody enterprise however, with the usual spate of rapine pillaging. The land would be honourably acquired with a spirit of honesty and fair treatment, a circumstance that was aided substantially by the vastness of the New World and its sparse indigenous population. Ralegh had already brought two young men from the Algonkian nation, Wanchese and Manteo, back to England to immerse them in the cultural nuances of  Elizabethan London, and, whilst there, were given the freedom of Durham House, before being repatriated, under the aegis of Harriot, in their native Virginia.

By all accounts, Harriot carried out his duties with great diligence and enthusiasm, learning the ‘queer’ tongue of the Algonkians and immersing himself in their rich culture and religious beliefs. Although one of the goals of such a mission was to take the Christian faith to the native Americans, it was not to be imposed. That said, Harriot found no shortage of Algonkians who embraced the life of Christ, finding that their truths were part of a greater truth.

Harriot produced a famous treatise, A Briefe and True Report of the New Found Land in Virginia, published in 1588, of his dealings with the peoples of this new territory, and marking him out as arguably the father of modern ethnology.

According to Dr. Allan Chapman, a renowned historian of science at the University of Oxford, and fellow Christian, whom this author has had the immense pleasure of conversing with on several occasions, Harriot could also be said to be the founding father of scientific education in North America. In his True Report, Harriot appeared to give a lecture, presumably in the Algonkian tongue, to a native American audience, who were dumb struck by the cleverness of the scientific instruments he brought with him from England:

Mathematicall Instruments, Sea Compasses, the virtue of the Loadstone in drawing yron, a Perspective Glasse which shewd manie strange sightes. Burning Glasses, wide fire woorkes, Gunnes…Spring Clocks that seem to goe of themselves, and many other things that we had.

Some historians have used the accounts of the various optical devices described in his True Report, as evidence that there may have been a ‘Tudor telescope’,significantly predating those eventually acquired by Harriot. Yet, as Chapman points out in his book, Stargazers, Copernicus, Galileo, the Telescope and the Church, this is a classic case of reading too much into the literature:

The strange sights and images which seemed to perplex and even alarm the Roanoke locals, I suspect were probably no more than the facial and other distortions that anyone can see in a convex or concave mirror.

pp 261

Thomas Harriot was an accomplished mathematician; one of the finest in England. Most notably perhaps, he introduced the symbols for less than (<) and greater than (>) which are used to solve inequations. Harriot also did original work on the binomial theorem, which is an eminently useful technique for the expansion of algebraic expressions raised to any power.

When Ralegh asked Harriot to investigate the science of gunnery in the 1590s, he applied a vector based technique to resolve the projectile’s velocity into horizontal and vertical components and was able to deduce that its path fitted that of a parabola; an essentially modern analysis. He did however retain some outdated (and completely incorrect) ideas on motion, adhering to the ancient Aristotelian idea that heavier objects fall to earth faster than lighter objects.

Having a life-long interest in optics, Harriot formulated a theory of refraction in 1601, noting that when a ray of light passes from a thinner to a denser medium, the angle to which it is refracted from the point at which it enters the glass is always in the same proportion to the angle at which the ray first strikes the glass. This result, known more generally as Snell’s Law, was independently discovered by the Dutch scientist Willebrord Snellus (1580-1626) in 1621.

After Queen Elizabeth I died in March 1603, ending the line of the Tudors, James VI of Scotland ascended to the throne as James I, uniting the crowns of England and Scotland in the process. The new King, unlike Elizabeth before him, strongly disliked Sir Walter Ralegh. Indeed, just a few short months after the passing of Elizabeth, James I had Ralegh put on trial for treason. Though many scholars now consider the evidence against him to be specious at best, he was found guilty, sentenced to death, inexplicably reprieved from the gallows and condemned to spending the rest of his days under house arrest in the Tower of London. Despite this change of events, Harriot visited Ralegh at the Tower on many occasions, remaining loyal to his friend and patron.

It is important to remember that though Ralegh were imprisoned in the Tower, he still enjoyed considerable liberties, uncannily similar to Galileo’s ‘house arrest’. A far cry from the dark, dank and rat infested dungeons, they were given comfortable lodgings, enjoying fine food and drink, and freedom to roam within its walls, attend Church, and carry out day to day investigations and studies. Even their families were permitted to live there. So, despite his ‘imprisonment,’ it was still possible for Ralegh to live out a reasonably fulfilled life.

Harriot himself was not immune to the suspicions of the new regime, having being imprisoned in the Tower for three weeks, cross examined but summarily released in November 1605. Harriot’s loyalty was rewarded when Ralegh recommended him to Henry Percy, the Ninth Earl of Northumberland (1564-1632), who was also imprisoned for 17 years in the Tower for being a Catholic sympathiser and for his alleged involvement in the plot to blow up the Houses of Parliament in 1605. Fabulously wealthy, the ‘exotic’ Percy was rumoured to have spent an unprecedented £50 a year on books and employed Harriot to carry on his scientific investigations. For this he was given a very generous stipend and access to Percy’s stately southern residence at Syon Park, Brentford, London and a comfortable residence at Threadneedle Street in the city. Overnight, Harriot not only became financially independent but was now the richest mathematician in Europe, commanding a salary estimated to be ten times greater than the best paid academics of the age!

According to his 17th century biographer, John Aubrey, Harriot waded into all of the pressing astronomical questions of his day. “He had seen nine Cometes,” wrote Aubrey, “and had predicted Seaven of them, but did not tell how.” Intriguingly, according to Dr. Chapman, Harriot may have co-discovered the elliptical nature of the planetary orbits traditionally ascribed to the work of the German astronomer and mathematician, Johannes Kepler. According to his friend and protégé, Sir William Lower, while pressing his master to compile a list of notable scientific achievements later in his life, left this tantalising snippet:

“……..long since you told me as much [of Kepler], that the motions of the planets were not perfect circles,” and that the planets made their, “revolutions in Ellipses”.

In this matter Chapman leaves us with a proverbial cliff hanger, raising the question: “One wonders exactly how long since?”

Ibid pp 265

What is certain, however, is that Harriot, being a geometer of some renown and thus intimately acquainted with the mathematics of orbits, would have had extensive correspondence with the other great intellectuals of the age, Johannes Kepler included. Furthermore, there is no evidence that Harriot cultivated the notion that he had arrived at the formula of the ellipse to explain the orbit of Mars. Indeed, in stark contrast to the vast majority of learned men of his time, Harriot never published anything after his True Report of 1588, which came as a source of considerable irritation to his patrons, who wished only to seek glory for his accomplishments, as well as to his friends, who watched in anguish as others trumpeted their ‘discoveries’, which were probably best attributed to Harriot himself. This was a characteristic that was to set Thomas Harriot apart from his contemporaries, who invariably identified knowledge with power. Perhaps a quote from King Solomon can help the reader grapple with this peculiar attitude to his work;

And I turned myself to behold wisdom, and madness, and folly: for what can the man do that cometh after the king? even that which hath been already done.

Then I saw that wisdom excelleth folly, as far as light excelleth darkness.

 The wise man’s eyes are in his head; but the fool walketh in darkness: and I myself perceived also that one event happeneth to them all.

Then said I in my heart, As it happeneth to the fool, so it happeneth even to me; and why was I then more wise? Then I said in my heart, that this also is vanity.

Ecclesiates 2:12-15

Despite vigorous researches over many decades and centuries, historians of science cannot unequivocally attribute the invention of the first refracting telescope to any one individual. And though rumours abounded that there were telescopic devices significantly earlier than those that came on the scene in the early 17th century, it is undoubtedly the case that the enterprisng spectacle maker, Hans Lippershey, based in the Dutch town of Middleburg, tried but ultimately failed to secure what would have been a lucrative patent in 1608 from the Dutch States General for the simple telescopes he constructed.

As a result, the device, which consisted of a matched pair of convex and concave lenses arranged in a tube, could be fashioned and sold by anyone once the proverbial cat was out of the bag. It is likely that Harriot acquired an early ‘dutch trunke‘ or ‘cylinder‘ from one commercial source in Holland early in the year 1609. Possible clues to the construction of the instrument can be viewed at the bottom of this Telescope 400 link

From the grounds of Syon Park, Harriot and his assistant, Christopher Tooke, set up the telescope, magnifying just 6 times, on the fair evening of July 26, and at 9pm turned his instrument on a five-day-old crescent Moon and began to sketch what he saw. Various mare are included in the sketch including the Mare Crisium, Tranquilitatis and Fecunditatis, as well as some rugged lunar features situated along the terminator, which modern scholars have identified as Theophilus and Cyrillus. Curiously, this first sketch, which can be seen in this link, does not record any craters, although 6x is certainly large enough to resolve several of the more prominent ones.

A spyglass like this launched the telescopic career of Charles Grover.

The author’s 6x achromatic spyglass used to substantiate Harriot’s observations.

Out of sheer curiosity, in a separate investigation, this author used a modern spyglass with an uncoated, one inch diameter object glass, also having a magnification of 6x, in the wee small hours (01:30h UT) of January 1 2016, to record observations of the last quarter Moon and Jupiter, as they cleared the treetops in the eastern sky. Like Harriot’s telescope, the spyglass gives an erect, correctly orientated image but enjoys a much larger field of view (~ 4 angular degrees). Nonetheless, this author could confirm that many lunar craters can indeed be observed with a steady hand, as well as clearly showing various maria. Turning to Jupiter, then just a few degrees above the Moon, the telescope could clearly reveal four Galilean satellites all to one side of the planet. The author made a sketch of this sight, shown below;

A quick sketch made by the author using a 6x achromatic spyglass showing the positions of the 4 Galilean satellites positioned to the northwest of the planet at 01:30h UT, January 1st, 2015.

A quick sketch made by the author using a 6x achromatic spyglass showing the positions of the 4 Galilean satellites positioned to the northwest of the planet at 01:30h UT, January 1st, 2016.

It will come as somewhat of a surprise to the modern reader not acquainted with a Galilean telescope that, despite its very low magnifying power, its field of view was very restrictive – typically 15 to 18 minutes of arc, or just over half the diameter of the full Moon. As a result, Harriot could not have seen the entire countenance of the crescent. Incredibly, though Harriot made many more drawings of the Moon, some of which display far more cartographic details than Galileo’s later drawings, were left undated. This has proved frustrating from the point of view of the modern historian, although when we take into account the radically different personalities of both Galileo and Harriot, we can see that both men had entirely different agendas. Harriot, having spent time in Virginia, was a draughtsman and well acquainted with map making. His methods were slow and methodical. Harriot was not seeking fame and fortune in the same way that Galileo was, and, according to Dr. Chapman, because Harriot had two high profile friends on ‘death row’ in the Tower, he had little desire to make himself ‘conspicuous.’

Ibid, pp  268.

By the winter of 1609, Harriot despatched Tooke, his able technician, to the residence of Sir William Lower at Trefenti, Carmarthenshire, South Wales, instructing him to fashion several other Galilean cylinders so that he and his philosophical friends, a one Mr. Vaughan and Mr. Protheroe (and possibly a few others), could begin their own telescopic investigations of the Moon and other celestial bodies. The surviving exchanges between Harrriot and the ‘Carmartenshire philosophers’, clearly reveal their avowed acceptance of the Copernican system as well as Kepler’s elliptical orbital theory. This is the earliest known record of an ‘astronomical society’, the members of which were to confirm Galileo’s monumental telescopic work by observing the Galilean satellites and the erstwhile invisible stars in the Pleiades.

Over the next few years, Harriot was to complete his now famous Moon maps as well as embarking upon a detailed study of the Sun. His method involved observing the Sun when it was near the horizon and veiled behind mist and thin cloud (the reader should, under no circumstances, attempt such an observation!!). Harriot was the co-discover of sunspots, recording them at or about the same time as Galileo, and possibly earlier than Christopher Scheiner (1573-1650) and Johannes Fabricius (1587-1616), which, in themselves, provided more evidence against the time-honoured cosmology of Ptolemy.

Christoph Scheiner( 1573-1650), the Jesuit priest and astronomer

Christoph Scheiner( 1573-1650), the Jesuit priest and astronomer, with his telescope featured to his left.

 

 

 

 

 

 

 

 

 

 

 

 

 

Over the next two years, Harriot was to carry out some 450 observations of the Sun, never once claiming their discovery, observing how they moved across its otherwise brilliant face, breaking up and sometimes even disappearing. Indeed, modern scholars were able to establish a solar rotation period of 27.154 days from Harriot’s drawings – uncannily close to the modern accepted value of 27.2753 days. This affirms the accuracy and attention to detail so central to Harriot’s modus operandi.

According to Dr. Chapman, Tooke may have made improvements to the basic Dutch ‘trunke’ and referrring to a study conducted by the distinguished historian of astronomy and cosmology, the late Professor John North (1934-2008), identified no less than six telescopes associated with Harriot and the ‘Trefentine’ philosophers, ranging in power from 6x to 50x.

ibid, pp 272

Tooke is likely to be the first bona fide telescope maker in Britain, an optical tradition that was to be continued over the following centuries.

Although Harriot embraced the Christian message from his youth, even writing the Lord’s Prayer in the Algonkian language, some scholars have suggested that he may have experienced a brief religious hiatus in his middle years. Doubtless, the revolution heralded by the application of the telescope to the celestial realm had raised new questions in the minds of his learned contemporaries. Why were the astronomical bodies puckered and imperfect? How did God create everything from nothing? Was His divine hand needed at every stage, from the formation of atoms to the completion of worlds? Was the allegory of the Universe even attributed to a personal God or was it merely blind chance?

Although Chapman acknowledges that nothing firm can be adduced from Harriot’s surviving notes and correspondences, he is inclined to the view that the world’s first telescopic astronomer re-embraced his Christian heritage in the final decade of his life, as evidenced by his 1615 correspondence with the King’s physician, Sir Theodore Mayerne, who assured Harriot of the certainty of the existence of ‘one all-powerful God’. From his days in Virgina, Harriot had taken to ‘drinking’ tobacco smoke, as the Elizabethans had referred to it. Earlier physicians had hailed the new wonder drug as an effective remedy to counter the ‘dangerous moist humours of the body.’ 30 years of heavy inhalation of tobacco smoke was to take its toll on Harriot’s health and he had developed a cancerous lesion on his nose.

Ibid, pp 273

Because many tumours of this sort have a tendency to metastasise, spreading to other organs of the body via the lymph nodes, Harriot was arguably history’s first clearly attested tobacco-induced cancer victim, dying on July 2, 1621. Receiving a full Christian burial, he was laid to rest at his local Parish Church of St. Christopher-le-Stocks, located in the heart of the City of London. And while the Church was razed to the ground by the Great Fire of 1666 and another resurrected on the original site by none other than Sir Christopher Wren (1632-1723), this too was eventually demolished in 1781 to make way for a grand new building that would became the headquarters of the Bank of England. In the 1970s however, the gravestone dedicated to Thomas Harriot was recovered and, in his honour, a new plaque carrying his gravestone inscription was unveiled inside the bank.

It is difficult to crystallize the legacy of Thomas Harriot, being so far removed from him in time, but these words come to mind; learned, diligent, enterprising, kind, loyal, uncompetitive, humble and God-fearing. Despite not marrying and raising children, he lived out a fulfilled life without a bad word to say about his fellow men, and rendered all the more remarkable owing to his great wealth and life-long connection with the rich and powerful.

England’s first telescopic astronomer, Thomas Harriot (1560-1621) gaudeamus!

Further Reading:

Chapman, A., Stargazers: Copernicus, Galileo,the Telescope and the Church, (2014), Lion Books.

North, J., The Fontana History of Astronomy and Cosmology, (1994), Fontana Press.

You can read more about the great visual observers of antiquity in my up-and-coming book, Tales from the Golden Age of Astronomy.

De Fideli

An Evening with Octavius.

Octavius, my 8 inch f/6 Newtonian in the Cold of Mid-Winter.

Octavius, my 8 inch f/6 Newtonian in the cold of mid-Winter.

 

 

 

 

 

 

 

 

 

 

Prove all things; hold fast that which is good.

                                                                                1 Thessalonians 5:21


Date: Saturday, December 12, 2015

Time of observation: 22:00-23:30 UT

Temperature at commencement: -3C

Temperature at termination: -4C

Seeing: Ant I -1.5, transparency excellent, no wind.

Instrument: Well-collimated 20cm f/6 Newtonian (22 % CO). Standard Skywatcher Dob focuser. No fans employed.

Materials & Methods: A suite of double stars observed with the Newtonian, being mindful of magnifications used, aesthetics of the image garnered, and efficacy of the splits on a range of systems of varying degrees of difficulty. Mark III Baader Hyperion Zoom and dedicated 2.25x Barlow, 1.25″ Baader Neodymium filter, Parks Gold 7.5mm ocular. Instrument sat upon a Lazy Suzan Dob mount (undriven). Instrument moved from a warm and dry domestic setting to a cold and dry unheated shed, where it remained for several hours until its deployment at 22:00 UT. Flexi-dew shield attached.

Observations: One good night can dispel a myth and expose a fallacy. This time it pertains to the notion that small refractors are better suited to winter viewing and that reflectors or compound, catadioptric instruments can only do useful work in the warmer months of spring and summer.

This is a misleading notion and simply untrue. Nor is it supported by the weight of historical evidence, which shows that large Newtonians were used to great effect by some of the finest and most admired observers of past generations. The work of the great Victorian, Reverend T.W. Webb, is just one example. As we have explored previously, Webb chose to use a 9.25” With-Berthon silver-on-glass reflector to carry out observations in all weathers, including freezing winter nights. Nor did Webb employ active cooling to his telescope as no such device was available for him to use.

Octavius, my 8-inch f/6 Newtonian (also without active cooling fans) performed flawlessly this evening when turned on a variety of double stars, the Airy disks of which were observed as tiny, round, calm and beautifully resolved. Despite the large temperature differential between my body and the surrounding air, a warm insulating coat, gloves and hat greatly reduce heat loss. Attaching a dew shield to the end of the tube increased the distance between my body and the entrance pupil. All these measures and a steady atmosphere conspired to produce arguably the finest images of double stars I have seen in any telescope.

theta Aurigae: Very easily resolved at 160x but even more compelling at 360x, both the primary (magnitude 2.6) and secondary (magnitude 7.6) separated by about 4 seconds of arc. This system can be quite tricky, owing to the large magnitude differential between the components. A magnificent sight!

Rigel: Despite its low altitude, the exceptionally calm air made seeing the feeble spark from its companion child’s play at 60 diameters or above.

The theta1 Orionis complex: The 8-inch speculum showed all six of the Trapezium stars A through F at magnifications of 360x, the magnitude +11 E and F components becoming ever more distinct as one’s eyes became better adapted to the dark.

Alnitak: The easternmost star in Orion’s belt. The 8-inch telescope at 150x showed its whitish, magnitude 3.7 companion just 2.5” away to the south southeast of the magnitude 1.9 primary.

Mintaka: Very easy at all powers. The primary shines in a soft white colour but the companion, located a decent 52” away to the north presents as a beautiful, pale blue cast in the 8-inch speculum.

eta Orionis: Much more challenging but the decent aperture made very light work of this system at 360x. The telescope showed its very tight companion a mere 1.8” east northeast of the primary. This is a fetching colour-contrast double, faithfully rendered in the perfectly achromatic reflector, with the primary appearing yellow and its companion blue.
32 Orionis: The pair was perfectly resolved at 360x.The primary (magnitude 4.4) and its secondary ( magnitude 5.7) separated by 1.8”

52 Orionis: a classic Dawes pair of 6th magnitude luminaries, brilliant white and well separated by 1” using a magnification of 360x.

42 Orionis: Very impressed with this system, which was not as difficult as I had anticipated! Though only separated by 1.1”, the difficulty here is the very large brightness differential between the primary and secondary (4.6/ 7.5), the raw resolving power of the 8-inch aperture (360x) in these excellent conditions rendering the split easily.

eta Geminorum: The icing on the cake on this frigid evening! I have given mention to this orange variable star (magnitude ~3.5) in previous communications. Although I have glimpsed (and I mean glimpsed) the very faint secondary in 4- and 5-inch refractors as well as 17cm f/16 Maksutov at very high powers, the image in the 8 inch reflector was in a completely different league! My notes from the evening of January 29, 2015, using a 17cm Maksutov Cassegrain revealed the companion using a glare-reducing variable polarising filter at 340x and at a recorded temperature of -5C. That being said, the superior resolution of the 8 inch speculum was all too obvious to my eye, for it revealed the dim (magnitude 6.5) bluish secondary just 1.6” off to the west-southwest of the ochre primary more plainly than I have ever seen before in any telescope! And this was true even though the system was still a few hours away from meridian passage! The superiority of aperture being abundantly apparent, I watched eta for many minutes, savouring the sight which I had dreamed of seeing for many years.

Concluding Comments: Despite the cold, the Newtonian telescope worked perfectly well. Laziness and wilful scaremongering have prevented many from using their larger Newtonians to good effect under these conditions. The observations made this evening reaffirm the importance of aperture-dependent resolving power working under ideal meteorological conditions. They are supported by three tiers of evidence; physics, history and personal experience. Don’t let anyone stop you from discovering the genius of Newtonian optics! If you don’t try, how will you ever know? And as to the wisdom of confining one’s observations to aperture-limited refractors in winter, that’s all well and good, but bear in mind that you’ll be missing out on golden opportunities to see more, much more!

 

De Fideli

 

The Great Meudon Refractor

The 83cm Refractor at Meudon Observatory, Paris.

The 83cm Refractor at Meudon Observatory, Paris.

 

 

 

 

 

 

 

 

 

 

 

 

 

A Work Dedicated to the Sovereign People of France.

 

The great refractors always have their place in modern astronomical observation, through the purity and quality of their images. At Meudon, beneath the great dome, a resolving power of 14 hundredths of an arc second awaits the observer. Very few institutions in France can offer as much.

                                                                                              Dr. Paul Couteau (1923-2014)

At the beginning of the 21st Century, the stakes have changed: astronomers no longer count upon the Grande Lunette to open the way to new discoveries, but wish above all to utlise it to share with the largest number of people the passion of observation, the fascination with planets and nebulae; that will be the new career of this fantastic instrument.

                                                                                              Professor Daniel Egret

                                                           President, Paris Observatory.

Founding Days

Tucked away in a leafy southwestern suburb of Paris, amid rolling hills and valleys, and sleepy glades of chestnut and ancient oak, lies Meudon. Inhabited since Neolithic times, the Gallic incumbents called it Moldum. Under Roman occupation from the mid-1st century B.C onwards, it was known as Moldunum. The great natural beauty of the area attracted the elite in French society from these early times, its hills providing ready made vantage points for surveying and surveillance alike. During the decadent reign of Louis Quatorze, the Sun King, its most famous building, the Château de Meudon, became a favourite hunting retreat. Raped and pillaged during the Bloody Revolution, more misfortune befell the Château in 1795, when a fire all but razed it to the ground. By 1803, its demolition complete, one would be forgiven for thinking that anything good could come of it. But like the mythical Phoenix rising from its own ashes, the site had attracted many astronomers over the years and was ‘re-discovered’ by the great French astronomer, Pierre Jules Janssen (1824-1907), when he surveyed the area by balloon in the 1870s. After lobbying government officials, he persuaded them to dedicate the site to a new world power; scientific knowledge. Keen to maintain its imperial prestige, the French government commissioned Janssen with the ambitious task of building a state-of-the-art astronomical observatory on the ruins of the erstwhile stately grounds.

Demolition of the Château of Meudon by Hubert Robert.

Demolition of the Château de Meudon by Hubert Robert.

Under the aegis of Janssen, repair work commenced on the buildings, as well as the in situ restoration of astronomical equipment; kit that had been abandoned over the years and fallen into disuse. The offices and laboratories were lodged in the principal part of the estate, which formerly consisted of a modest château, stables, and an assortment of other outbuildings. A separate building, the Château Neuf, built by Mansart in 1706, was to be restored and topped by an astronomical dome 18.5 metres in diameter.

Building work commenced in 1890 and continued for five years. The chief architect appointed to the project, monsieur C. Moyaut, had all the upper wings of the château removed and restored the ground floor, being careful to preserve the stylized pediments created by Mansart at the beginning of the 18th century. In 1886, work began on the construction of a 20 metre-diameter circular space that was to form the lower walls of the observatory and upon which a rotating dome would be constructed. The obvious choice to build the dome was Gustave Eiffel, who had directed the construction of the large dome at Nice Observatory and was a personal friend of Janssen. However, it seems that Eiffel was too preoccupied with erecting the famous Parisian landmark which bears his name to commit to such a project. The contract to construct the 18.5 metre dome was thus awarded to the Anciens Etablissements Cail, a firm which specialised in large iron works and which had previous experience constructing a lesser, 12.5 metre diameter dome for the Observatory at Rio de Janeiro, Brazil. After many stops and starts and some serious injuries inflicted upon some of the workmen, the fully rotating dome was finally signed off on the morning of June 14 1895.

The state-of-the-art equatorial mounting of the refractor was erected upon a pedestal of cast iron, which in turn rested on a massive pier measuring 4.1 x 2.7 m in cross section and soaring 18 metres above the floor. The entire structure was designed and built by Paul Gautier (1842-1909) in his Parisian workshop at 56 boulevard Arago.  Structurally and mechanically, it was very similar to the mounting provided by Gautier for the newly completed 77cm (30-inch) Nice refractor, which saw first light in 1886. A spiral staircase wound its way upwards around the pier and led the astronomer to the observing platform, which could be adjusted in elevation to accommodate the changing altitude of the celestial object under study. The platform, which is 8 metres wide and 2 metres deep, is affixed to the rotating dome. The equatorial mount could subtend an arc length of 30 degrees ensuring vibration free movement for two hours, after which time an alarm sounded, summoning the astronomer to return the sector to the start of its travel, interrupting observations for a short time.

Side view of the great 77cm ( 30-inch) Nice refractor showing the design of its massive equatorial mounting.

Side view of the great 77cm ( 30-inch) Nice refractor showing the design of its massive equatorial mounting.

Dedicating the Instrument

By the end of the 19th century, the art of melting, homogenising and casting high quality glass blanks was in a relatively advanced state. Janssen commissioned the work of France’s finest opticians, the brothers Henry, to produce the crown and flint object glass for the Meudon refractor. Since 1882, they had moved their optical workshops to the Montrouge, a commune of southern Paris, and a conveniently short distance from the new observatory. Breaking somewhat with convention, the Henry brothers settled on a contact Littrow design for the main objective, which consisted of an equiconvex front lens followed by a negative lens of the same inner radius, with the last surface being flat. This design made it relatively easy to fabricate to very high standards. A second crown object glass of the same aperture was fashioned and kept in storage.

The distinguished French astronomer, Audouin Dollfus ( 1924-2010).

The distinguished French astronomer, Audouin Dollfus ( 1924-2010), who spent his entire professional career at Meudon.

According to the late Audouin Dollfus (1924-2010), resident astronomer at Meudon for 60 years between 1945 and 2005, the two large lenses had a measured diameter of 82.95 centimetres but when they were fitted inside their cell, the clear aperture was reduced to 80.6cm. The chromatic correction of the object glass was optimised at 594nm. With a focal length of 16.397 (~f/20) metres (measured at the green spectral line of mercury), it displayed some secondary spectrum at blue-violet wavelengths. That being said, according to Dollfus, this could be completely eliminated by using a simple yellow filter. The assembled object glass was mounted in its tube in 1893, a full three years before work on the revolving dome had been completed and was tested by pointing the telescope at stellar point sources that crossed the slit of the motionless dome. The quality of the images was very well documented, having being tested by some of the finest optical evaluators of the age. For example, in 1929, the famous optical tester Bernard Lyot wrote concerning the large Meudon object glass:

“When the atmospheric conditions are favourable, the objective gives perfect images, necessitating a magnification of 800.”

Dollfus, A., The Great Refractor of Meudon Observatory,pp 22

In another test, carried out on the night of May 22 1937 by staff astronomer Fernand Baldet, a star of magnitude 6.3 was examined with a power of 2,300 diameters, recording “a perfectly circular diffraction pattern surrounded by broken moving rings.”

According to Dollfus, in further tests conducted between 1966 and 1975, resident Meudon astronomer, Paul Muller, examined numerous double stars and could cleanly separate pairs as close as 0.15 arc seconds, and others showing strong elongation at 0.12 seconds of arc!

Jean Texereau, chief optician at the Paris Observatory, performed modern optical testing methods on the object glass.Wave testing showed the figure to be perfect over the central 68cm, reaching 1/4 wave P-V at its extremities. Texereau recorded a slight turned edge in the outer 5.5cm which he attributed to stress of the glass within the cell.

Collectively, these testimonies reveal that this 19th century object glass was performing at or very near the theoretical limits imposed by its aperture.

This will come as a considerable shock to contemporary amateur astronomers, who remain largely ignorant of the prowess of long focal length achromatic refractors. Furthermore, the testimonies of these professionals yet again flatly contradict the proclamations of some contemporary amateurs who have claimed that apochromatic refractors perform better. Self evidently, the latter remain an expedient luxury for double star astrometry and, as we shall see, many other enterprises besides.

Janssen was also mindful of the advances photography could bring to his science and because the 83cm refractor was designed for visual observations, he set about ways of mounting a second telescope which was to be devoted to photographic use. Thus, in essence, the Meudon refractor would not be singular but double! The best emulsions of the day – gelatin silver bromide – were sensitive to short wavelength (320-410nm) radiation and so the photographic telescope would have to have an optimum chromatic correction at 430nm. A second object glass of 62 cm aperture and focal length 15.9 metres was to be mounted alongside the visual instrument. This photographic objective saw first light in 1898 and was operated by Henri Deslandres and his assistants, who took some of the first long exposure photos of globular clusters and the enigmatic nebulae, as well as planetary surfaces. The same objective produced very high quality spectra of spectroscopic binaries and Nova Persei, which erupted onto the scene in 1901. The same instrument was used to deduce the rotation period of Uranus (via the Doppler effect) in the following year. And in 1903, the 62 cm astrograph delivered some spectacular images of Comet Borrely.

The drawtube of La Grande Lunette, equipped with a fine rack and pinion focuser, could accept six large, long focal length eyepieces offering magnifications from 220 to 540 diameters. A further half dozen short focal length oculars extended the magnification range up to an astonishing 2,300x! Remarkably, a specially designed low power, wide-angle ocular delivered an enlargement of 150x diameters and a field of view of about half an angular degree. Furthermore, an ingeniously designed metal stage equipped with two micrometer screws enabled the eyepiece to be moved up to 6 inches up or down, or from side to side, and in so doing, extending the field of view considerably. The workshops of Gautier fashioned a precision bifilar micrometer, with platinum wires to be used with the great telescope to measure the angular separation of double stars as well as planetary and satellite diameters. Sadly, the skill of the artisans who fashioned these pieces has waned in the modern psyche, being largely lost to the work-a-day world.  The effort and time lavished upon them, every last part, bit, appendage, preserves in the learned man’s eye, the true value of good work, an honest day’s grind.

And, of course, those perfect little imperfections!

These instruments were statements; they were built to last, made with human hands, hearts and minds!

To the left of the focuser was mounted a plate holder to rigidly hold the 24 x 24 cm square photographic plates which collected the focused light from the 62 cm astrograph and covered a field of view nearly three quarters of an angular degree in diameter.

La Grand Lunette was fitted with several auxiliary refractors serving a variety of purposes. The principal finder was a powerful, long focus 15cm (6-inch) achromatic telescope. It had two main functions. In the first instance, the instrument was used to assess the seeing conditions on any given night, which in turn would dictate what types of objects were to be studied and the magnifications to be employed in their pursuit. It also acted as a precision guiding telescope during long exposure astrographs taken with the 62 cm astrograph. In its earliest years of use, the astronomer would operate a handle to move the telescope in declination and a cord that enabled fine motion control in right ascension. The original clock drive, located at the base of the great double telescope, is controlled by a tangent screw which turned slowly and regularly and was powered by a heavy weight that slowly unwound from a cable affixed to a larger drum. When the weight had fallen through its maximum distance, it had to be rewound by means a large crank which demanded considerable muscle power from the astronomer who happened to be on duty.

The mechanisation of La Grande Lunette did not stand still. As soon as new technologies came to the fore, the directors of Meudon Observatory sought to assimilate them. We shall not dwell on such matters, but suffice it say that the dome and the telescope drive were eventually powered by electricity generated in situ by dynamos and gas powered motors. And thanks to the efforts of Dr. Paul Muller during the 1960s, the observing platform was eventually replaced by a moving floor, which could be precisely adjusted in height as the telescope was moved to observe objects of differing altitude. Such refinements were to maintain the great Meudon double refractor as one of the crown jewels of the French scientific establishment throughout the twentieth century.

The great double refractor at Meudon was dedicated at a time when new technologies were being employed to revolutionise our understanding of the Universe. In particular, the new science of spectroscopy was being applied to studying the celestial bodies, both in the Solar System and beyond. In January 1898, the brilliant French astronomer, Henri Alexandre Deslandres (1853-1948), was appointed as staff astronomer at Meudon and would spend the next six years applying his considerable skills at the telescope and serving as the Observatory’s Director later in his career. In particular, Deslandres had gained expert instruction in the use of the spectroscope during his time at the Paris Observatory (1889-97), where he had used the 1.2m reflector, as well as inventing the spectroheliograph, an instrument that served to greatly advance our knowledge of the Sun. Deslandres quickly set the Meudon telescope to work measuring radial velocities of stars and studying the dynamics of spectroscopic binary systems.

Since 1895, Deslandres had been devising new ways to use spectroscopy to garner information about the rotational characteristics of the planetary bodies. At the Paris Observatory, he had already obtained solid spectroscopic evidence for the rotation of the rings of Saturn, but owing to its much greater distance and smaller size, the rotational aspects of Uranus had not been elucidated. This was further exacerbated by the paucity of atmospheric features on the planet that could lend themselves to visual tracking, as well as its large axial tilt, allowing only a residual component (i.e. spectroscopically inclined) of its rotational velocity to be measured. The method was straightforward in principle but difficult to achieve in practice. Specifically, as a planet rotates, the limb approaching us displays spectral lines that are redshifted and, correspondingly, are blue shifted as they recede from us on the opposite limb. After many trials and simulations, Deslandres, together with his assistant Burton, managed to obtain high quality spectra of the planet’s limbs during the summer of 1902, and from these data, deduced something quite amazing:

“It is very probable that the planet Uranus rotates in a retrograde sense, like its satellites.”

ibid, pp 68

Using similar techniques, Deslandres measured the rotation periods of Jupiter and Saturn (and its glorious rings) to high precision.

Watchers of the Planets

Come, let us learn something of the culture of the great planetary observers of old.

To make his observations, Antoniadi installed himself behind the eyepiece of the refractor in darkness. Fixing upon a particular region of the planet’s disk, he watched the image, moving or quivering through the effects of atmospheric turbulence.He looked to seize upon the favourable moments in order to furtively catch the finest details and to engrave them upon his memory. Thus he practiced the exercise upon another region. After having thereby memorised the different configurations, he arranged them with respect to each other. Finally, leaving the eyepiece, he placed himself behind a table with an empty desktop upon the observing platform. With  pencil and eraser, he sketched upon paper at a single sitting all the memorised features of the planet.

ibid pp 77.

A time honoured sketch of Mars, made by Eugene M. Antoniadi using the Great Meudon Refractor.

A time honoured sketch of Mars, made by Eugene M. Antoniadi, using the Great Meudon Refractor.

 

 

 

 

 

 

 

 

 

 

 

 

While Meudon Observatory was never without a planetary observer from its inception, they were all eclipsed by the skilful eye of Eugene Michael Antoniadi (1870-1944). Born in Constantinople and of Greek nationality, the world was Antoniadi’s country. Cultured, refined, a man of letters, Antoniadi made his reputation in France after he had worked under the eccentric, Camille Flammarion(1842-1925), who had set up a grand private observatory at Juvisy. Flammarion, a Darwinist and leading member of the French spiritist movement, was, naturally enough, also an ardent supporter of the Martian canal theory, championed by Giovanni Schiaparelli (1835-1919) and Percival Lowell (1855-1916), having popularised in his voluminous writings, the notion that extra-terrestrial life was a cosmic certainty.

The great planetary astronomer, Eugene M. Antoniadi (1870-1944).

The great planetary astronomer, Eugene M. Antoniadi (1870-1944).

And though Flammarion was in possession of a formidable refracting telescope of 9 inch aperture (by Bardou), Antoniadi was keenly aware of the superiority of the 83cm Meudon refractor for the up-and-coming 1909 Martian opposition. Accordingly, he wrote to Deslandres, the then Director of Meudon Observatory, informing him that he would offer his services as ‘Astronome Voluntaire’. It was an offer Deslandres couldn’t refuse. Antoniadi’s most famous work on Mars began on the evening of September 20 1909, when he observed the Red Planet under exceptionally fine seeing conditions. La Grande Lunette showed him details that were hopelessly beyond the power of Flammarion’s instruments, and yet intriguingly, there was no sign of the canals. It was a revelation to the young planetary observer:

The planet appeared covered with a vast and incredible amount of detail held steadily, all natural and logical, irregular and chequered, from which geometry was conspicuous by its complete absence.

ibid pp73

Received wisdom insists that planetary sketching be done at the telescope, but that was not Antoniadi’s modus operandi. As recalled by Dr. Dollfus, he would rather commit his observations to memory before attempting a sketch. Curiously, this author ‘discovered’ the effectiveness of this method (at least for planets) whilst studying Jupiter in the 2014-2015 apparition using a 18cm Maksutov, and, more recently, using the author’s most powerful telescope.

King Solomon of old was most correct; there is nothing new under the Sun!

In so far as what is known, E. M. Antoniadi faciebat!

Antoniadi spent the next few decades, on and off, observing the planets and their principal satellites. By 1930, having amassed an astonishing array of detailed drawings of Mars, and having corresponded with other first-rate observers across the world using equally powerful telescopes, was able to lay the fabled Martian canals to rest; they were simply optical illusions. Antoniadi did however entertain a less grandiose vision of Martian life; he believed the seasonal waves of darkening that occurred during Martian Spring were tracts of vegetation. This idea was entertained right up until the advent of the Space Age.

Antoniadi’s fine drawings of Jupiter and Saturn reveal the workings of an exquisitely trained eye. The amount of detail visible through La Grande Lunette often necessitated sectional drawings of the turbulent atmospheres of the giant planets. Curiously, though the instrument could take much higher powers, Antoniadi’s sketches show that he preferred modest enlargements of 500x or so on bright planetary disks like Jupiter. This serves to remind the reader that excess powers can be counterproductive in the study of low contrast details on planetary surfaces.

Antoniadi also spent many hours drawing the various albedo features on the Galilean satellites using a routine power of between 500 and 800 diameters. Adhering to the tried and trusted culture of note making (which is sadly in great decline in the present epoch), he explained how the best details could often be made out while the satellites crossed in front of the planet, the bright background providing the contrast needed to pick off the finest details. Indeed, he claimed that observing the satellites against a dark sky was far less productive in this capacity.

The great stability of the images garnered by the 83cm Meudon refractor allowed extremely accurate micrometer measurements of the angular sizes of the Galilean satellites to be divined. What is more, the drawings he made of the surface features of these satellites enabled him to deduce that they were tidally locked, that is, presenting the same face to the planet as they orbit Jupiter. After Antoniadi’s retirement from active service, other astronomers at Meudon, including A. Dollfus, Bernard Lyot and Henri Camichel were able to assemble the first detailed maps of their surfaces in the early 1940s.

On the Physical Nature of the Planetary Bodies

The great Meudon refractor was also instrumental in advancing our knowledge of the physics and chemistry of many solar system bodies. One of the pioneering techniques developed by Meudon scientists was astronomical polarimetry. Ordinary sunlight consists of transverse electromagnetic waves that vibrate in every direction, that is, they are unpolarised. Upon reflection from a planetary body, certain planes of vibration are enhanced and others attenuated. The degree to which this occurs depends on the nature of the reflecting surface. For example, a smooth and polished surface produces a strong enhancement in certain directions, while a matt surface produces a comparatively weaker enhancement. Furthermore, opaque materials produce much stronger polarisations than that of a transparent material. What is more, the distribution of matter within a body also effects the polarisation profile obtained. For example, light reflected from a solid surface has a very different polarisation profile to that obtained from a cloud made of discrete, interspersed particles of ice or water say. By carefully studying the nature and degree of polarisation enhancement on a test object, one can also deduce the sizes of the particles comprising it.

Chief Astronomer at the Meudon Observatory in 1943 and received the Bruce Medal in 1947

Bernard Lyot ( 1897-1952) who became Chief Astronomer at the Meudon Observatory in 1943 and the recipient of the prestigious Bruce Medal in 1947 , as well as the Gold Medal of the Royal Astronomical Society.

In 1922, Bernard Lyot fashioned a prototype fringe polarimeter to be tested on a small 17.5 cm refractor, but later modified it for use with the great 83cm Meudon telescope. Once the object was centred in the telescopic field, one would look through the polarimeter and observe a series of jagged fringes representing the various polarisation enhancements, changing in intensity as the angle of inclination was varied. The device had a built-in ‘compensator’ which enabled the investigator to introduce an equal but opposite amount of polarization that nulled the individual fringes. Lyot steadily improved the sensitivity of the instrument to measure tiny polarisations, of the order of one part per thousand. The great image scale and stability afforded by La Grande Lunette enabled small sections of a given planetary body to be individually analysed, thereby recording regional differences in the physio-chemical makeup of the body.

Turning the great refractor upon the Moon, Dr. Lyot was able to reach a remarkable conclusion;

The Moon must be covered by dusts having a composition similar to that of our terrestrial volcanic ashes.

Ibid pp 97.

The planet Venus, long shrouded in mystery, also yielded some of her secrets under the watchful eye of La Grande Lunette. The polarisation curves obtained for this planet were strikingly different to those obtained for other bodies where the reflection came from a solid surface. Instead, Lyot deduced that the data was consistent with an upper atmospheric layer consisting of very fine droplets, some 2 microns in size, and having a refractive index  ‘within the range of water’ (1.33)

As the technique was refined and extended to other wavebands in later years, stretching into the infrared and ultraviolet, Meudon astronomers were able to detect innumerable transparent particles in the Cytherean atmosphere, spherical in form, with a radius of 1.05 microns, and a refractive index of 1.44. The substance that best fitted these data was concentrated sulphuric acid!

When Lyot applied these techniques to Mars, and in particular, having compared the polarimetry curves of the so-called ‘seas’ and ‘continents’ he concluded that there was little to choose between them and that if anything, they resembled the dusty surface of the Moon. Lyot’s pioneering polarimetry measurements also could distinguish between yellow dust clouds, and whiter clouds, often seen on the morning limb of the planet, composed of transparent particles, more characteristic of hoar frost or some such. Little by little, the unbridled machinations of mankind were being tempered by the unrelenting march of scientific progress.

Exploring the High Energy Universe
In the wee small hours of December 13 1934, the English amateur astronomer, Manning Prentice, observing from the small market town of Stowmarket, Suffolk, discovered a magnitude 3.4 star that was previously invisible in the constellation of Hercules. The nova reached its peak brightness of +1.5 just over a week later, on the evening of December 22. When the astronomers at Meudon were alerted to this nova La Grande Lunette was set to work to record its spectrum. During a three week period during March 1935, staff astronomer, Henri Camichel had managed to obtain 32 spectra of the object, which by then had faded back to magnitude 4.1, remaining so until month’s end after which it slowly faded out of view. The spectra revealed numerous emission lines, some known and some unknown, which were broadened with two equal maxima with a separation that corresponded to radial velocities from 590 to 870 km/s.

Visual inspection of the system by the staff astronomers at the Lick Observatory atop Mount Hamilton in California, revealed a stellar companion on the evening of July 4 1935. This was followed up by observations carried out by Fernand Baldet at Meudon, who charged the 83cm refractor with powers of 1600x to 2,300x confirming the duplicitous nature of the system. Baldet’s notes showed the stars to be of similar colour, separated by a mere 0.25 arc seconds but with no trace of nebulosity. By taking long-exposure spectra of the system into the autumn of 1935, Camichel was able to establish the essential nature of a cataclysmic variable star:

One can account for the particulars of the spectra by supposing that the star, at the moment of its peak brightness, ejected gaseous masses which were illuminated according to the excitation mechanism for planetary nebulae…. One could explain the doubling of the emission lines in terms of two very large masses moving in opposite directions. That hypothesis seems to be confirmed by the fact that the star was seen to be double.

Ibid pp 106

It is noteworthy how so many of the astronomers who, having used the great Meudon refractor for ultra-high resolution studies, spoke so highly of its virtues. Indeed, according to Dr. Dollfus, “It allowed visual scrutiny with very high magnifications, each time it was necessary.

ibid, pp 107

Once again, testimonies like these stand in sharp contradistinction to contemporary perceptions of the classical achromat, which unfortunately, are born of ignorance more than anything else.

Closing Years of Active Service

La Grande Lunette continued to be used though the latter half of the 20th century, its doors constantly opened to new generations of enthusiastic observers. Dr. Paul Muller, mentioned earlier, arrived at Meudon in 1956 after a spell at Strasbourg Observatory. Muller conducted a grand series of close double star measures with the telescope, collating his results in three publications. Systems as close as 0.12 seconds of arc were recorded in this archive. Another example is to be found in the work of the Japanese amateur astronomer, Shiro Ebisawa, who, beginning in 1968, travelled to Meudon to use the great refractor to continue his planetary studies for a few weeks at a time. A Mars specialist, Ebisawa made many fine drawings of the planet with the great refractor, as it progressed through its seasons. One new feature credited to Ebisawa’s impeccably trained eye is the so-called pre-polar hood, which manifests itself in the autumn of each Martian year and which preceded the deposition of fresh ice layers on the planet’s polar caps.

A very special event was celebrated at Meudon from July through December of 1988, when the Martian orb would once again swell to 24 seconds of arc, just as it did in that faithful year of 1909. The French Astronomical Society invited distinguished overseas observers to Meudon to conduct a series of commemorative visual observations of the Red Planet. Among them were Shiro Ebisawa (Japan), Dr. Richard McKim (future President of the BAA), from the United Kingdom, and the celebrated Italian observer, Marco Falorni, as well as a team of eight French-born observers, who enjoyed 100 clear nights out of 160 where the prodigious resolving power of the 83cm Meudon refractor was pressed into service. Many invaluable sketches of the planet were conducted during this time, in remembrance of the grand cultural tradition of visual observation conducted with such diligence in earlier decades. A similar but smaller scale program was carried out during the less favourable opposition of 1990, which yielded a further 45 detailed observations of the Red Planet.

The magnificent revolving dome erected over the historic telescope suffered terrible damage in the great storm of 1999, bringing to an abrupt end all work conducted at the observatory. But thanks to a generous grant awarded to the institution by the French Ministry of National Education, work on repairing the dome could commence, together with an ambitious program of telescope renovation. Such efforts will allow the great Meudon refractor to be enjoyed by an adoring public well into the 21st century. In the words of the late Professor A. Dollfus, “La Grande Lunettte makes people dream…..It has become legendary, an exceptional instrument symbolising a way of thinking and practicing Astronomy…. And the story is not over.”

Viva La France!

References & Further Reading

Dollfus, A. The Great Refractor of Meudon Observatory, (2013), Springer.
Sheehan, W., Planets and Perception, Telescopic Views and Interpretations, 1609-1909, (2015) University of Arizona Press; Reprint edition.
Sheehan, W. The Immortal Fire Within: The Life and Work of Edward Emerson Barnard, (2008), Cambridge University Press.


De Fideli

Taking Back Visual Astronomy II: Resolving Binary Stars with Newtonian Reflectors

Octavius the Progressive.

Octavius the Progressive.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 De omnibus dubitandum

The Newtonian reflector has a long and distinguished history among dedicated observational astronomers. With the advent of generous aperture, silver-on-glass mirrors in the late 19th century, many more amateurs could enter the field and make valuable contributions to the study of the Moon and planets. What’s more, their comparatively enormous light gathering power compared with traditional refractors made it possible to see new morphological details of hitherto elusive deep sky objects, thereby aiding in their classification.

The traditional instrument of choice in double star astronomy has been the classical refractor. With their long, native focal lengths and excellent thermal stability, they are especially adept at separating point sources at very high magnifications, at or near the theoretical limit imposed by their aperture. Refractors don’t scale well though and become impractically cumbersome and expensive in apertures above 6 inches (and if you really want to do sub arc second work you’ll need something larger anyway). I have demonstrated in earlier work that more economical telescope designs – the Maksutov Cassegrain in particular- can be excellent double star instruments. Having used a large, 17cm f/16 Maksutov continuously for a year, this author debunked a long standing assumption about these telescopes that prevented many from exploring their considerable charms. Specifically, some prominent amateurs, perhaps in some desperation to justify the purchase of much more expensive refractors, cultivated the idea that large Maksutovs (and, by implication, other catadioptrics) would not acclimate. This assertion was found to be largely unsubstantiated, after extensive field testing showed that these instruments can and do work well, even in winter.

In more recent times, this author has begun to explore anew the many attributes of the Newtonian reflector. As described in an earlier review lasting about six months, a closed-tube 8” f/6 Newtonian reflector was found to cool quickly (typically 40 minutes for a temperature differential of 20C) – significantly faster than even a 5 inch refractor. What is more, no cooling fan was deemed necessary and the telescope offered up excellent, high resolution images of planets like Jupiter. What was most surprising however, was its ability to split tricky double stars when contemporary wisdom said otherwise. This led to further investigation by examining the historical literature in order to establish whether Newtonians were ever used for double star astronomy and, if so, how efficacious they were in this capacity.

Having explored the life and work of the Reverend T.W. Webb (1806-1885), it came to my attention that the celebrated 19th century observer had indeed used a large 9.25 inch f/8 silver-on-glass reflector made by George With to resolve very tight pairs at or close to the limit imposed by its aperture. As a follow up, double star observer, John Nanson, alerted me to the work of an obscure British 19th century observer – Kenneth J. Tarrant – who employed a 10.25 inch Calver reflector (probably a f/7 or f/8 relative aperture) during the 1880s and 1890s to not only observe double stars, but to measure them also!

I would invite you to examine the documents presented here, noting the dates and seasons when the measures were made, thereby providing information on the frequency and likely conditions (like English summer temperature swings) under which observations were conducted – as well as the measures themselves, some of which show that the mirror was indeed capable of resolving pairs at or near the theoretical resolution of the telescope. I canvassed the opinion of the double star expert, Bob Argyle, based at the Institute of Astronomy, Cambridge, for his take on Tarrant’s data. Specifically, I asked Argyle whether there was anything in the Victorian amateur’s data that would stretch credulity, calling his attention to Tarrant’s measures of 25 Canum Venaticorum.

“As far as I can see, looking at Tarrant’s results, these are what I would expect from a good Calver telescope – in fact he did not seem to stretch the telescope very often. Specifically 25 CVn looks very plausible – the current WDS mags are 5.0 and 7.0 so it’s somewhat brighter than the values Tarrant gives (and currently at 1″.7).”
Tarrant’s measures demonstrate three things;

1. The British climate allowed him to frequently work to very high standards, which included sub arc second pairs.
2. The Calver reflector must have produced images stable enough for mensurative purposes.
3. Tight pairs with very significant brightness differences (up to two or three stellar magnitude differences) were also resolved.

Not much else is known about Tarrant however. “I don’t know of any other references to Tarrant’s work, “ said Arygle, “but he seemed to hold the BAA Double Star Section together before WWI finished it, and probably deserves a paper from one of the historical groups.”

In more recent times, a number of other observers using Newtonian reflectors have come to the fore. This author has already brought to your attention some of the ongoing work of Christopher Taylor, who employs an open-tubed 12.5 inch F/7 Calver reflector to watch a number of sub-arc second pairs moving rapidly in only a few years. You can see a few images of his telescope here. In addition, I am mindful of the work of the French double star observer, Jean-Francois Courtot, who has resolved pairs down to 0.66” using his homemade, 8-inch Newtonian since 1993.

It would also be worthwhile considering the portfolio of the well known astronomical artist, Jeremy Perez, who has sketched many double stars using both a 6″ f/8 and a 8″ f/6 Newtonian reflector, as well as the observations of Mircea Pteancu, who has used a 8″ f/6 reflector to successfully resolve sub-arc second pairs.

Thus, not only is there a historical precedent for the use of the Newtonian reflector in doing the kind of work traditionally associated with the classical refractor, but the notion that the former instruments would only be capable of such work in tropical or temperate climates is not supported by the evidence.

That said, not all Newtonians are equally well favoured to carry out such work!

To see why, we need to explore aspects of the physics of the Newtonian telescope.

Modern parabolic mirrors of decent quality are (or should be) essentially devoid of spherical aberration. The main optical defects in the Newtonian are due to other Seidel aberrations, particularly coma and astigmatism. Let C represent coma and A represent astigmatism.

Mathematically, the angular expansion (theta) of the image due to coma is given;

C = 3theta/(16F^2) where F is the focal ratio (relative aperture) of the telescope.

Astigmatism is given by:

A = ( D/2f) tan^2(theta), where f is the focal length of the telescope.

Since D/f = 1/F and if we consider small angles, where tan (theta) expressed in degrees ~ theta radians, the formula for astigmatism simplifies to;

A = (theta)^2/2F.

We can see from the formula for both C and A that coma (C) scales proportionately with theta while A scales as (theta)^2, so that for very small angles ( << 1 radian) it follows that coma will always overwhelm astigmatism in any properly executed mirror.

Let us now set the resolution of the telescope to the Dawes limit (in arc seconds) given by 4.56”/D
To convert this formula to radians, we need to do some more arithmetic.

1 degree = 60 x 60 = 3600”

Also 1 angular degree = 1/57.3 radians =0.017 radians

Thus if 0.017 radians = 3600” then 4.56” = (0,017/3600) x 4.56 radians = 2.21 x 10^-5 radians

So the Dawes formula expressed in radians is:

(2.21 x 10^-5)/ D where D is in inches.

For critical work at maximum resolution we may equate the expressions for coma and astigmatism with the Dawes limit;

Thus,

A + C = (2.21 x 10^-5)/D

But since A << C for any small angles (which is appropriate here), we may simplify this to just:

C = (2.21 x 10^-5)/D

Thus, since we have C = 3theta/(16F^2)

We get: (2.21 X 10^-5)/D = 3 theta/(16F^2).

Cross multiplying and rearranging, we obtain:

Theta = (16F^2 x 2.21 x 10^-5)/3D

Simplifying gives theta (in radians) = (1.18 x 10^-4 x F^2)/D

For convenience, we can now convert this formula to arc minutes;

1 arc minute = 1/60 degree = (1/60) /57.3 = 2.9 x 10^-4 radians

So, 1.18 x 10^-4 = (1.18 x 10^-4)/ 2.9 x 10 ^-4 = 0.407

Thus our final result is that

Theta (arc minutes) = (0.407F^2)/D.

We are now in a position to analyse what happens when we use various different numbers for the focal ratio (F). The formula predicts that for a constant aperture D, the maximum available field (theta) over which the image contains no appreciable aberrations scales as F^2.

This means that the faster the F ratio, the smaller the true field over which aberrations are minimized.

For example, a 8 inch f/6 mirror would have an optically corrected radius of (0.406 x 6^2)/8 = 1.83 arc minutes or 3.66 arc minutes in angular diameter. Doing the same math for F=5 and F=4 yields diameters of 2.54 and 1.62 arc minutes, respectively.

To see how this impacts work at the eyepiece, consider my own telescope, a 8” f/6 Newtonian. In order to get adequate image scale for sub-arc second pairs, I like to use a magnification of 548x (3.5mm Baader zoom and 1.6x Barlow). Since my eyepiece has an apparent field of 72 degrees, the true field available at this magnification will be 7.88 arc minutes [ that is (72/548) x 60]. Thus, the percentage (linear) of the field that gives perfect definition will be (3.66/7.88) x 100 ~ 50 per cent. When we get to an F/5 system, the percentage falls to just 30 per cent, and at F/4, a pesky 20 per cent!

One can see that at F/5 or faster, positioning the image of the double stars will become problematical, but that’s not the end of the story!

As anyone familiar with the operation of a Newtonian will tell you, the lower the F ratio, the harder it is to collimate the optics accurately. Indeed, the sensitivity to mis-collimation (a quantity called primary mirror axial error) in millimetres is given by the 0.022 x F^3. It follows that the wiggle room for a F/6 Newtonian will be a comfortable 4.8mm but just 2.8mm at F/5 and only 1.4mm at F/4!

What does all this mean?

In a nutshell, the faster the F ratio of the primary mirror, the smaller the true field at any given magnification that is truly free of aberrations and the greater the likelihood of mis-collimation. I was being kind when I described the result linearly; but when you recognise the relevant field area (which scales with r^2), you suddenly realise you’re in deep water. X marks the spot! LOLl

These are the principle reasons why an F/5  or faster Newtonian will be less likely to resolve to the Dawes limit. F/6 is about good enough – thank goodness for small mercies! – and anything slower is a bonus!***

This also agrees with my own experience, having never satisfactorily resolved sub arc second pairs with an F/5 or F/4 Newtonian. It also agrees with the aforementioned historical curiosities!

Look again at Tarrant’s measures of 25 CVn conducted in the summer of 1885.

Octavius; a ‘scope to believe in!

***Note added in proof: The above calculations do not preclude the possibility that a precisely aligned, fast Newtonians (f/5 or slower) can’t do this type of work  but rather serve to illustrate that the difficulty of achieving these high resolution results becomes more difficult as the F ratio falls. Investing more money in precision focusers and more exotic collimating devices can increase the odds of success, as could the possibility of introducing optical accoutrements like coma correctors (now being made by various manufacturers) into the optical train.

References

Bell, L The Telescope, Dover (1971)

R.W. Argyle (Ed.) Observing and Measuring Visual Double Stars, Springer (2012).

Results so far: In the last six months or so, I have had the privilege of using this fine SkyWatcher 8-inch f/6 Newtonian reflector. As explained in an earlier review, I modified the instrument by purchasing a smaller secondary mirror (22 per cent by diameter) made by Orion Optics, Newcastle Under Lyme, England. I could have reduced this further but I wanted the telescope to be an excellent all-rounder rather than just a one trick pony. Both the primary and the new secondary were treated to enhanced Hilux coatings, which significantly increased its light grasp, reduced scattered light around images and has a longevity that is guaranteed for at least 25 years. Such an instrument provides breath-taking views of the Moon and planets and serves up a 2.25 degree true field for stunning deep sky vistas.

Even before I had these modifications done, I was very impressed by its ability to resolve some tricky doubles and triple systems. On the best nights, stars present as tiny Airy disks, round as buttons, even at very high powers ( > 500x). The spherical correction of the mirror is excellent and displays no on-axis astigmatism, which is a definite show stopper for this kind of work. My best images yet came just a few nights ago, where on the mild evening of Friday, June 26 at 22:20 UT, I beheld the most striking image of Epsilon Bootis (340x) I have seen in just about any telescope! The components – a soft yellow primary and a royal blue secondary – were magnificently rendered with acres of dark sky separating them. The same was true when I examined Delta and Mu Cygni, as well as Pi Aquilae (1.5″); text book perfect renderings if ever I have seen them!

At twenty minutes past midnight on the morning of June 9 last, I managed to glimpse the elusive companion to Lambda Cygni (my best yet at this location, 0.9” and 1.6 stellar magnitude differential), convincing me that I could go still further.

My methodology is fairly straightforward and is based on the recommendations of Christopher Taylor, who I mentioned earlier.

• The telescope is checked for accurate alignment using an inexpensive laser collimator before the commencement of each vigil and backed up by careful star testing.

• Only stars above a certain minimum altitude are examined, not less than 35 degrees

• I use a Baader Neodymium Moon and Sky Glow filter, which darkens the twilit sky at my location, reduces glare from very bright stars, and retains a neutral colour balance.

• After charging the telescope with the appropriate optical power, the stellar image is swung to the east of the field and left to drift slowly into the centre, where it is critically examined by my eye. The above is repeated again and again until I am satisfied that what I am seeing is not a diffraction artifact or some such.

• The time, date and conditions, magnification etc are always recorded. And if at first you don’t succeed……. try try again Lol!

In my correspondence with Bob Argyle, he was kind enough to suggest two stellar systems which are especially ripe for study with the 8-inch speculum; 78 UMa, now conveniently located near the bright star Alioth in the Plough Handle (components have magnitudes 5.02 and 7.88, with a current separation of ~0.8”) and Tau Cygni (magnitudes 3.38 and 6.57 with an angular separation of 0.9”).

I will begin with 78 UMa, as it should be fairly easy to find near Alioth in the twilight.  I shall leave Tau Cygni to later in the season.

I will report back on my progress in due course.

If you have a similar ‘scope at home, why not give it a try too?

If these stars are not suitably located for you, seek out others of similar difficulty by looking up the WDS catalog.

This project will certainly tax your powers of observation.

It would be great to hear about your experiences!

 July 1, 2015

NB: Taylor used a ‘routine’ magnification of 825x with his 12.5 inch f/7 Calver to achieve separations of 0.35 -0.40″ pairs. May attempt slightly higher powers on my own (smaller, 8 inch) telescope, perhaps 600x plus?

Nae luck as yet. A heat wave has settled in over the UK. While southern Britain basks in sunshine, conditions have remained stubbornly sultry with lots of cloud hampering any attempts to track down UMa 78.

Attempted a brief vigil late in the evening of Friday, June 26. Although my ‘easier’ test systems mentioned above all looked excellent, cloud prevented me from locating  my target near Alioth. I did however ‘uncover’ a delightful new binary system about half a finder field away from Alioth; STF 1662 ( RA  12h 36 min, Dec: 56 34, magnitudes 7.83 an 9.75, separation 19.3″).

Just received word that my article on modifying the SkyWatcher Skyliner 200P will be featured in the August 2015 issue of Astronomy Now………hallelujah!

July 2, 2015

Time 22:50h UT

Ambient: Clear, good transparency, 14C, slight SW wind, strong twilight, seeing not so hot (Ant III-IV), midge flies legion.

Four ‘warm up’ systems  observed @ 340x

Epsilon 1&2 Lyrae: well resolved.

Epsilon Bootis: resolved with some distortion.

Delta Cygni: Companion seen periodically, but with some considerable distortion.

Pi Aql: Resolved fairly well but only occasionally.

A 1.5″ night. Little point in continuing. Packed up early.

 July 4, 2015

Happy Holidays to all my viewers in the United States!

Moi?

Semper eadem.

Weather still rather unsettled, very humid with lots of heavy down pours, so little else to report from my own observations.

Investigo: I love data and admire diligence. Though I don’t know him from Adam, the American amateur astronomer, Mr. Tom Bryant, gave me both in bucket loads!

Mr. Bryant has been very busy testing the performance of his C8 on hundreds of double stars from all across the heavens.

You can see the fruits of his considerable labours here.

Go on; have a good, long look at that huge list. Dates (all year round!!!), times, instruments, are recorded, and, crucially, the location of those observations.

Input! Input! Input!

Lol!

And I see he’s constantly updating (see the latest dates listed).

Way to go!

He’s done remarkably well on many sub-arc second pairs don’t you think?

0.7″ doesn’t seem too much of a stretch for him and he’s elongated pairs down to 0.5″!

Here’s a recent review of a modern C8.

This instrument has a central obstruction of ~ 35 per cent and takes a while to acclimate…. apparently.

Here’s  the climate data for Bethesda, MD, which is quite near Silver Spring, MD, where Mr. Byrant uses his C8 inside his cosy, wee observatory, Little Tycho.

Typing in the months, one by one, we see diurnal swings of about 10C throughout the year, and which is a little larger than those encountered at my location.

My 8″ f/6 Newtonian, with a 22 per cent central obstruction, ought to do just as well – if not better – would you not think?

Only the seeing and my laziness can limit its performance.

Surely?

 July 5, 2015

Some thoughts on a lazy, Sunday afternoon:

The diligence of Tom Bryant and Carlos has delivered treasures to them. Work pays.

God endowed King Solomon with wisdom because he desired it ahead of wealth and power.Still, because of his faith, the Lord gave Solomon all three, and in great abundance.

Yet, he was better at dispensing that wisdom to others than applying it to himself.

In the proverbs of that ancient King, we learn of the traps laziness sets for us;

No matter how much a lazy person may want something, he will never get it. A hard worker will get everything he wants. 

Proverbs 13:4

A lazy person is as bad as someone who is destructive.

Proverbs 18: 9

Why don’t lazy people ever get out of the house? What are they afraid of? Lions?

Proverbs: 26:13

Nuff said, eh?

20:30 UT

At last, another opportunity will likely present itself later this evening to visit 78 UMa.

With a bit of luck, I’ll have more to report back on soon enough.

But let’s not confuse ourselves. There is one telescope forum in particular that harbours a few lazy liars I’m in the processing of flushing out.

Folk who masquerade as being ‘experienced’ but ostensibly reveal very little of that quality. Nor do they show any real insight except that which they borrow from others.

They neither understand their observing environment, nor the kinds of instruments that would best work there. e.g. using a large, fast reflector to split low-altitude double stars in a desert?!

How dumb is that? Lol!

But this is just ignorance, and I’m willing to overlook that.
That said, there’s a more insidious side to all this, which I am not willing to overlook.

Lies, lies, porky pies.

You see, some individuals spend their time cultivating untruths about what can and can’t be done with certain telescopes, without ever testing these claims in a scientific way.

Worst still, they persist in maintaining these myths, despite the mounting counter-evidence presented to them.

I suppose it’s a form of blindness.

Why shouldn’t a Newtonian deliver the readies?

If you know, tell me; I’m all ears!.

iustitia! iustitia! iustitia!

July 6, 2015

00:20h BST.

Ambient: Mostly clear, tranquil, cool (10C), twilit.

Seeing: II-III

A better night tonight. Seeing fairly good.

All warm up systems beautifully resolved at 340x

0.9″ companion to Lambda Cygni well glimpsed at 548x during moments of better seeing

78 UMa: diffraction pattern examined on and off for 20 minutes at 548x. Higher powers found to be unhelpful. Companion unseen.

Heavy dew this evening.

Good, productive night, all in all.

22:25UT

Teeming down with rain tonight.

Thus far, it’s not the kind of Summer we enjoyed last year.

Still, when are two ever the same? lol

Moi?

Semper eadem.

It occurred to me that I’ve already achieved what I set out to demonstrate; that a decently executed Newtonian can be used to explore the dynamic realm of sub-arc second binary star astronomy; I mean, I’ve already bagged (a few times now) a 0.9″ with a sizable brightness differential (1.7), so anything beyond that just reaffirms my premise.

But I don’t think I’m being overly ambitious to work for something better. Do you?

I will continue to work with 78UMa until the skies get darker.

July 8, 2015

00:30h BST

Test everything; hold fast to what is good.

                                                                   1 Thessalonians 5:21

Ambient; mostly cloudy, 13.5C, a few patchy sucker holes opening and closing. Breezy (7mph westerlies).

Seeing: II, certainly a notch up on last night.

Only three test stars examined tonight; all images at 340x were clean and crisp but shaky in the wind.

Spent a few minutes on and off examining 78UMa at 340x and 544x. Complex diffraction image, no elongation observed at 544x, so the companion must be ‘disembodied’ from the primary (Airy disk round as a button). Wind and cloud making detailed observations very difficult. Companion unseen.

I have noticed, going back through my notes, and again tonight, that on windier evenings, the images through the Newtonian can look especially fine. I have thought about why this might be. Perhaps the breeze circulates the air inside the tube more efficiently and might be ‘brushing off’ any boundary layer that might be on the mirror?

I think there is something in this.

Mother Nature lending a helping hand, just as she must have done with other observers using their specula over the decades and centuries.

Thank goodness for the wind!

09:50h BST

Last night was most interesting. Not much in the way of systems observed but the quality of the images in the modest wind was duly noted.

It was such a simple revelation to me that I cannot help but think it is universally true.

My previous observing records with refractors and a large Maksutov have shown that good to excellent seeing can accompany windy weather. I look back fondly at the wonderful skies of last Summer, where I got superb results with a 17cm Maksutov. I note especially my observations made on the evening of July 16, 2014, where the Maksutov cleanly resolved Lambda Cygni  during a windy (9mph) spell.

In the case of the Newtonian, I think windy conditions can have additional benefits in improving image quality, independent of the seeing.

Open air observing with Newtonians appears to be a good thing and I shall continue with this custom.

Might a fan be beneficial?

Maybees aye, maybees naw.

Would I consider installing one?

No.Ohxi.

I get enough breezy evenings in a year to continue as I am.

Besides, I am willing to bet that the foolishness of the wind is smarter than the ingenuity of any man-made fan.

A curious aside: Our Victorian friend, Kenneth J. Tarrant, observed 25 CVn with his Calver reflector on the 189th day of the year. Curiously this was July 8, 1885 – almost exactly 130 years ago today!

LoL!

I found some old British archives for the general weather for that month here.

I note that in this meteorological document, for the dates July 7-11, there were ‘favorable South-westerly winds in most places’.

Might  Mr. Tarrant have enjoyed a few breezy evenings when he made these measures?

I wonder!

July 9, 2015

00:20h BST

Ambient: Clear, cloudless sky, very beautiful twilight, no ground wind, unseasonably cold (6.5C), seeing III-IV. Cool Arctic air flow tonight; bright stars scintillating strongly.

Test systems all resolved, but the more difficult ones not so cleanly. U78Ma examined at 340x an 544x but too turbulent to study.

Vigil aborted.

11:20h BST

I have been thinking about the wind again and how best to use it. When Mr. Tarrant observed 25 CVn, his telescope would have pointed westward, towards Canes Venatici, and if there were a southwesterly breeze during the time he observed the system, some part of it would have blown over his Calver primary mirror.

This immediately presented a simple activity that I could use profitably during breezy evenings. When first placed outside, I could remove the cap that covers the front of the instrument and point the telescope directly into the prevailing winds. That way, the air would be blown over the mirror and it would help expel any ‘stagnant’ air inside the tube.

When observing an object in a part of the sky away from the natural direction of the wind for any prolonged period of time, I could swing the instrument back into the natural air flow  periodically, for a minute or two perhaps, before resuming my work.

I did some searching this morning to ascertain if anyone had recommended this procedure, either in printed texts or online. To my astonishment, I came up with nothing.

Maybe you know better?

In addition, I have been looking at images of those silver-on-glass reflectors of old (existing before the era of the electric fan) and noticed that many of the tubes have little hinged  ‘windows’ at the side, near the primary mirror, so as to assist (presumably) the circulation of air in the optical train. I may consider something along these lines myself; perhaps drilling a coupe of small holes on opposite sides of the tube and fitting a fine wire gauze over them to enable air to flow through but not particulates.

I can make the wind work harder for me.

Something to think about anyways.

To my chagrin, more unsettled weather is forecast for the weekend ahead.

Mair anon..

July 13, 2015

23:45h BST

Ambient: almost entirely clear, tranquil skies, seeing excellent (I-II), 10C, humidity high.

Success!

Started on Delta Cygni (340x) and was rewarded with a beautiful calm image! Companion resolved from its primary by a veritable country mile.

Pi Aql: Very cleanly resolved (340x) even at less than optimal altitude.

78UMa: Companion seen fairly well, roughly due east of the primary and inside first Fraunhofer diffraction ring. Glimpsed at 22:50h but better seen at 23:30h.  Checked the WDS data on the system Der Admiral sent me the other week. Its estimated position angle of ~118 degrees agrees fairly well with my observation.

No’ bad ken.

Where next Columbus? LOL

Anyone following me?

Vigil ended owing to heavy dew.

July 14, 2015

Bastille Day, New Horizons hurtles past Pluto, ken.

20:00h

Consummatum est.

No more to prove. No more work to be done. No one left to fight.

A 8 inch f/6 reflector can indeed be used to resolve sub arc second pairs. You don’t need an expensive telescope to do it.

A little preparation and the determination to succeed is all that is required.

And one good night.

I contacted Bruce MacEvoy, who I had the pleasure of meeting in California a few years back. He will be editing a brand new edition of the Cambridge Double Star Atlas. Bruce followed my work with the Maksutov and, more recently, the Newtonian reflector. After congratulating him on his new role, I reminded him that he had a responsibility not to cultivate untruths about the types of telescopes that can and cannot do high resolution double star work. He assured me that the atlas will not endorse the fallacy that one type of telescope is superior to others.

Satis.

Nota Bene: November 29, 2015: Dave Cotterell, based in Ontario, Canada, posted a string of high resolution images of double stars – some quite tricky for any telescope – using his 12.5″ f/6.5 Newtonian, thereby providing more evidence that these instruments can and do make excellent double star ‘scopes. In addition, he has reported his visual results here, using the same instrument, showing that he was able to cleanly resolve pairs down to 0.5″ or  0.6″. Well done Dave!

De Fideli

 

A Historic Clark Telescope Receives a New Lease of Life

The newly refurbished 24-inch Clark refractor used by Percival owell to carry out his Martian observations. Image courtesy of Sarah Conant, Lowell Observatory.

The newly refurbished 24-inch Clark refractor used by Percival owell to carry out his Martian observations. Image courtesy of Sarah Conant, Lowell Observatory.

In the last decade of the 19th century, the wealthy Bostonian oligarch, Percival Lowell, established a grand Observatory atop Mars Hill, Flagstaff, Arizona, some 7,250 feet above sea level. Here, in 1894, Lowell had installed a magnificent 24 inch refracting telescope, built by the famous American telescope maker, Alvan Clark & Sons. Nearly a century after Lowell’’s death, the telescope has been refurbished and will wow the public with spectacular views of the night sky.

An Eye on Mars
Bought for the princely sum of $20,000 ($500,000 in today’s money), the telescopes long focal length was ideal for viewing the planets. But there was one world in particular that captured Lowell’s imagination: Mars. Back in 1877, the Italian astronomer Giovanni Schiaparelli, had reported seeing networks of linear features on the Martian surface, which he interpreted as ‘canali’, or ‘channels’ but he later believed them to be artificial, works of intelligent minds. This was dynamite to Percivall Lowell, who dedicated many years of his life to studying the Red planet through pristine mountain air, far from the lights of towns and cities. Lowell’s many drawings of Mars showed up even more canals than Schiaparelli, many of which were seen to extend from the polar ice caps to the parched equatorial deserts, Lowell published his views in three books: Mars (1895), Mars and Its Canals (1906), and Mars as the Abode of Life (1908). In these writings, Lowell combined his misguided faith in Darwinian evolution with the latest theories in planetology to popularise the idea of an advanced race of intelligent beings desperately trying to survive on a dying planet. Lowell’s far-fetched ideas inspired others to create a new generation of science fiction literature, most celebrated of which was H. G. Wells’ influential The War of the Worlds.

Ultimately, many of Lowell’s ideas turned out to be false. When other highly experienced observers, such as E.E. Barnard and Eugene Antoniadi, who had access to larger refracting telescope than Lowell’s 24-inch, examined the Martian disk, they could not see any linear features. Indeed, they maintained that when seen through larger telescopes, the so-called canals resolved down to darkly shaded dots that looked completely natural and not artificial as Lowell had contended. World-wide fame and affection soon turned to ridicule, as more and more evidence was amassed against his fanciful theory of advanced Martian beings. Perhaps the most scathing of all came from the British naturalist, Alfred Russell Wallace, who quipped that only a race of madmen would construct canals on this small desert world.

Another view of the restored 24-inch Clark at Lowell Observatory. Image courtesy of Kevin Schindler, Lowell Observatory.

Another view of the restored 24-inch Clark at Lowell Observatory. Image courtesy of Kevin Schindler, Lowell Observatory.

A Revered Instrument
Because of its unique provenance, the 24-inch Clark refractor at Lowell Observatory became one of the most celebrated telescopes in the history of astronomy. The late Sir Patrick Moore once claimed that it was his favourite telescope. The instrument was massive, fully 32.1 feet (9.77 metres) in length (f/16) with a tube made of riveted steel. Lowell mounted two other instruments alongside the main telescope, also refractors of 12-inch and 6-inch aperture, either of which could have served as the centrepiece of a small college observatory in their own right. The telescope was placed on a massive, state-of-the art equatorial mount. The vaulted dome in which the great telescope was housed, was designed by an ex-cowboy turned machinist, Godfrey Sykes, and was erected from hatchet-hewn ponderosa pine timber by a team of ten labourers in as many days!

A New Career in Education
After Percival Lowell passed away in 1916, the 24-inch continued to be used for research but in recent years it has been complete dedicated to public outreach, attracting about 85,000 visitors per year. As one might imagine, time has taken its toll on the famous instrument and in 2015 the staff at Lowell Observatory initiated an extensive refurbishment project for the 24-inch Clark. I contacted Kevin Schindler, resident historian at Lowell observatory, who kindly answered some questions I had about the project.

What was the primary motivation for restoring the Lowell 24-inch Clark refractor?

“The main reason was the telescope getting more and more difficult to move in recent years, said Schindler, “The telescope is moved by hand, and historically a person could actually push it with one finger. But by 2013, it was so hard to push that some people simply weren’t strong enough to push it. Plus, the telescope had developed a tendency to “clunk” when moved in a certain position, and this was clearly getting worse. As it turns out (we didn’t know this until the telescope was disassembled), both problems were caused by flattening of the main bearing. A new bearing was built and now those problems are gone. The old clock driven mount has also been replaced by a state-of-the art goto system to greatly speed up the pointing of the telescope during public out reach events.”

How much money had to be raised to fund the cost of the telescope’s restoration? Did the team receive any grants or bursaries to meet costs?

We raised nearly $300,000 for the project, Schindler explained, “ Two different sources – a private individual named Joe Orr (since deceased) and the Toomey Foundation for the Natural Sciences each contributed $100,000. We also raised money via crowd-sourcing efforts and many individual contributions”.

Could you provide a brief break down of the individuals/firms involved in refurbishing the instrument and which projects were assigned to whom?

The majority of work was done in-house,” Schindler told me, “under the management of Lowell’s Director of Technical Services, Ralph Nye. Other Lowell staff that played significant roles included: Peter Rosenthal, who refurbished most of the telescope controls (including a full powder coating for the tube) and ancillary parts, Jeff Gehring, who machined many new parts for the telescope, Glenn Hill, who refurbished walls and floor of the dome, and Dave Shuck, who created a new landscape outside the dome. Others were involved, and the people listed above helped out each other, but this is the basic leadership duties of the project.”

How do you think these restorations will be received by the public?

“The public will be quite excited about the restoration,” explained Schindler, “the Clark is one of the primary reasons visitors come to Lowell. They’ll be thrilled both because the telescope will be working better than ever, making for a more pleasant viewing experience, and also because the telescope is now visually stunning. Also, the Clark Telescope has been in Flagstaff since 1896, and its dome is an icon of the Flagstaff skyline. It is a cherished part of the very fabric of Flagstaff.”

Will the instrument continue to be used to train undergraduates and/or as a research instrument in its own right?

“The telescope will be used solely for public education, Schindler told me, “The Observatory is open seven days and six nights per week, and the telescope is a critical part of both the day and night-time experience. No plans are on the table to use it for research, and undergraduates will continue to be trained on modern research telescopes.”
In addition to the mechanical work, the massive, air-spaced doublet objective of the Clark had to be carefully cleaned. Over the last few years, brush fires have laden the air thick with sooty particulates which were deposited on the outer surface of the lens, decreasing its light transmission and increasing light scatter in the images. This has necessitated the removal of the lens cell from the telescope every two years or so for cleaning.

Many observers have visited Lowell observatory over the years and commented on the fine views the telescope has delivered. For many, the 24-inch Clark represents arguably the finest telescope made by Alvan Clark & Sons. Although the firm did produce larger instruments, such as the 36-inch Lick and 40-inch at Yerkes Observatory, the sheer weight of the glass has caused them to warp under their own weight. The 24-inch, in contrast, has not warped over the years and still provides stunning views of the heavens.

A large crane removes the telescope mount for refurbishment. Image credit: Kevin Schindler, Lowell Observatory

A large crane removes the telescope mount for refurbishment. Image credit: Kevin Schindler, Lowell Observatory

Splendid Views
I asked Kevin Schindler to tell me about some of the most memorable views he has enjoyed through the Clark over the years. “Regarding memories of excellent seeing conditions, two come to mind,” Schindler explained, “ the first must have been in the early 2000s. I had looked through the Clark for years by that time, but this was the first time the conditions were good enough to slip a 14mm eyepiece into the Clark and, for the first time for me, resolve Jupiter’s moons as disks; I could also clearly distinguish some colour, and this experience was almost surreal in its splendour. The other time was during the 2003 Mars opposition, distinguishing Phobos and Deimos. That was not visually stunning but a 10 on the coolness scale.”

As amateur astronomers, we all hope that the restorations to this iconic telescope will inspire a whole new generation of star gazers. And while there is most certainly no life on Mars as Lowell understood so, the spirit of his legacy lives on as we continue to look skywards for answers to our deepest questions.

Homo unius libri

Neil English is writing a new book chronicling the history of visual astronomy; Tales from the Golden Age of Astronomy. The author would like to thank Josh Bangle and Kevin Schindler of Lowell Observatory for sparing the time to answer questions.

Optimising a 8-inch Newtonian for Visual Use

Based on an article which originally appeared in the peer-reviewed  Astronomy Now magazine (August 2015).

Telescopes 101

200POver the last decade or so, amateur astronomers have become increasingly obsessed with acquiring very expensive apochromatic refractors that offer near optically perfect views under good conditions, but are limited by their restrictive aperture. I have heard people claim that a 4- or 5-inch Apo refractor gives ‘better ‘images than an 8-inch reflector on planets for example. This is patently nonsense, as the 8 inch Newtonian has twice the aperture and much more light gathering power than any 4 inch refractor, no matter what its pedigree. So what is going on here? As I said elsewhere, this is a pleasant fiction.  The view through the smaller ‘scope might look nice from moment to moment but that’s only because it can’t resolve finer detail that the larger telescope can, but at the expense of being more sensitive to the vagaries of the atmosphere.  In other words, the smaller ‘scope conceals far more than it displays; its beauty merely skin deep. Rest assured though, when the Newtonian is working optimally it will not only yield ‘prettier’ images than the refractor but they will be a whole lot more detailed too. That’s just physics.

After many years of testing telescopes of every conceivable size and genre, I have come to the conclusion that a good 8-inch F/6 Newtonian provides the biggest bang for buck in today’s market. It offers decent aperture for both planetary work and deep sky observing, with a generous 2.25 degree field. It is portable and acclimates quickly, often without the need for cooling fans. With a focal ratio of f/6 it works quite well with even budget wide-angle eyepieces and is capable of being accurately collimated during daylight hours. One of the best examples comes from the SkyWatcher Skyliner range of Dobsonians, which can be purchased as an entire package for less than £300, including delivery to your door. Having purchased this telescope, I wanted to demonstrate ways in which a very good instrument can be further improved to give the best possible images – improvements that do not incur a large outlay of additional funds.

Tube modifications
Refractors tend to have very well baffled tubes that stop stray light from flooding into the optical train especially in comparison to economically priced Newtonians. But through some simple measures, you can help control this stray light reaching the eyepiece. One of the most important things that needs to be done is to flock the region of the tube immediately opposite the telescope focuser. Many astronomy retailers sell rolls of flocking material costing just a few pounds. I simply cut off a piece of this material measuring 6 x 8 inches and stuck it onto the inside of the tube immediately opposite the focuser. In addition, the drawtube of the focuser was similarly flocked.

Flocking the tube opposite the focuser is a good move.

Flocking the tube opposite the focuser is a good move.

Mirror Modifications
The secondary mirror in the Newtonian is usually elliptical in shape and is orientated such that its minor axis minimizes the size of the central obstruction that is all too important in producing images rich in contrast. The mirror supplied with the Skywatcher Skyliner 200P has a minor axis diameter of 50mm, thus providing a central obstruction of 25% by aperture. And while this is perfectly acceptable for all round use, a number of alterations can be made to the secondary to improve the telescope’s overall performance.

A new 44mm flat with edges blackened with matt black paint.

A new 44mm flat with edges blackened with matt black paint.

 

 

 

 

 

 

 

 

 

 I contacted Orion Optics UK, based at Newcastle Under Lyme, Staffordshire, who have a long-standing expertise in delivering quality Newtonian and Maksutov Cassegrain optics to discriminating observers. In particular, they have developed their highly regarded Hilux enhanced coatings with 97 per cent reflectivity and were also able to make to order any secondary size I wanted. At first, I had intended to get the existing SkyWatcher secondary and primary Hilux coated and to purchase an additional secondary with a 36mm diameter for high resolution work. But in the end I decided to settle on a single flat with a diameter of 44mm, thus providing a very modest 22 per cent central obstruction. This size of flat also means that I can employ wide-angle two inch eyepieces without imparting too much in the way of vignetting at the edge of the field. Finally, before mounting the new secondary, I blackened its edges with matt black blackboard paint.

Inserting a cooling fan to blow cool air over the surface area of the primary mirror would help to accelerate the telescope’s acclimation but, truth be told, I haven’t found the need for one. The telescope will acclimate in about 40 minutes if taken from a warm indoor room to the cool of the night air. What’s more, if the instrument is left in a dry, unheated shed, it will be in a permanent, ‘grab ‘n’ go state.

Performance in the field
The telescope was mounted atop an inexpensive water butt with the mushroom knobs on the base of the lazy Suzan mount slotted directly into two pre-drilled holes of the butt. Such a measure raised the telescope to a decent height off the ground and kept the base free from dirt and grime. The modified 8 inch Newtonian has the same contrast transfer as 6-inch refractor (200-44mm) and, owing to its ultra-high reflectivity coatings considerably greater light gathering power. All in, the telescope and its modifications came to less than £550. How does it perform? In a word; splendidly! But to elaborate, I’ve enjoyed some of my very best views of Jupiter with this telescope. Indeed, they are every bit as good as a 6 inch apochromatic refractor costing five to ten times more! And contrary to popular belief, a 8” f/6 Newtonian is no slouch on double stars. You just have to look at the superlative work done by astronomical artist, Jeremey Perez, who uses a similar telescope to see why. During a spell of good, clear weather I was able to cleanly resolve the tricky pairs , Iota Leonis, Mu Cygni and Eta Geminorum – systems that are more challenging with an excellent 12.7 cm  f/12 refractor and 17cm f/16 Maksutov. Subsequent work has shown that the same telescope can resolve sub arcsecond pairs, again, within the remit of its aperture.

Deep sky objects really come alive in an 8-inch telescope. I have enjoyed some beautifully crisp views of the Double Cluster (Caldwell 14) and its star-studded hinterland at 30x. Spring galaxies like M81, M82 in Ursa Major and M51 in Canes Venatici are very well presented and a joy to study at medium and high powers. All in all, this was an enjoyable and worthwhile project to undertake and has transformed a good telescope into a great one!

Octavius: instrument of change.

Octavius: on solid ground.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For further details see my related articles here and here.

Two more threads that you might find interesting can be viewed here and here.

In this thread, the poster uses a 12.5″ f/6.5 Newtonian to resolve pairs down to 0.5- or 0.6″, as well as posting actual images of other pairs here.

Post scriptum: The Premo-Dob manufacturer Teeter’s Telescopes are now using GSO mirrors in their Dobsonian line. As Rob Teeter openly acknowledges, the optical quality of these mirrors is generally excellent. These are the same quality mirrors that went into the telescope highlighted above. So, like I said elsewhere, I wouldn’t trade my 8-inch Newtonian for any 6-inch refractor on Earth! Why would I?

Neil English is author of Choosing and Using a Dobsonian Telescope.

De Fideli

A Little Prinz from my Youth

                              By Paul Brierley, Macclesfield, England
In 1976 my father bought from Dixons, a 60mm F11 “Prinz” refractor.  As a young boy, mad about astronomy, I thought all my dreams had come true!
Dad would take it outside and show me the Moon and stars. I well remember my first views of “Lunar” through it, and I was instantly hooked. The telescope came with a very rickety altazimuth mount, together with three Huygens eyepiece, a Barlow lens, Moon filter
and the dreaded solar filter.
A 60mm f/11 Prinze gets a new lease of life. All images courtesy Paul Brierley.

A 60mm f/11 Prinze gets a new lease of life. All images courtesy Paul Brierley.

The telescope was used on most nights during the winter of 1976 and during the latter years of the 1970s and early 1980s. I was able to see Jupiter and Saturn, and using projection, our Star.
I well remember trying to record my observations, but soon gave up. The mount was just too unstable. If you sneezed it would wobble. Eventually the scope fell into disuse.  I don’t know what happened to its mounting, but, I kept the optical tube assembly.
In  2015, I decided that I wanted to use this telescope again, and this followed an evening of astro-imaging, when  I was happily downloading CCD images from another telescope. I decided to dig out the “Prinz”  The Moon had risen and I was able to view it, with the telescope handheld.
The Prinz achromat on a sturdy modern mount.

The Prinz achromat on a sturdy modern mount.

I have an adaptor that allows the use of modern Plossls and Orthos. I looked and was stunned by the quality of the telescopes optics. I decided there and then, to restore it, and put into service again.
On August 22-23, I started work.I stripped down the optical tube assembly and re-painted it. I took the optics out of it’s cell and carefully cleaned them. I used Optical Wonder Fluid, from Baader. Now they have been cleaned. The doublet lens is as good as new, with no sign of fungus or scratches.
I took up play in the focuser and found a mounting bracket for the optical tube. The tube was originally white, but I didn’t have any suitable paint. So, I painted the tube matt black, using black pipe paint. It looks as good as new, and now the focuser slop has been removed. Images stay central during focus. I can now use this telescope again.  I  can mount the optical tube onto my Acuter Merlin mount, and I am happy to say, unlike 1976., it is very stable.
It saw first light once again on August 28 2015. Once again, It was the Moon that took the glory. The view through a 18mm Volcano Ortho was very impressive.  I believe the lens has a single magnesium fluoride anti-reflection coating but does a fine job.  The Moon was very sharp with no colour fringing visible. I would hesitate to say that I think this telescope, although only a doublet achromat, is similar to a modern ED Apo in optical quality. I will use this telescope from now on, for lunar and planetary observation, together with high resolution imaging of the Moon, using a QHY5II-M camera.
An August Moon, as captured by the 60mm Prinz.

An August Moon, as captured by the 60mm Prinz.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

My sincere thanks to Paul for sending on this short article about a special little telescope that sparked his lifelong interest in astronomy. He is a member of the BAA, SPA, Webb DSS, as well as Macclesfield Astronomical Society.

De Fideli