Tales from the Golden Age: A Short Commentary on Walter Scott Houston’s “Deep Sky Wonders” Part II

A Distillation of observing notes from the late Walter Scott Houston(1912–93)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 8: August (continued)

Summer lies hot and tranquil on the land. The gigantic storms of winter and the turbulent atmosphere that accompanies them are only memories now. At this time of year the seeing is steady all night.

West of the Meridian in late evening lie the great star fields dancing with the brilliance of Sagittarius, Scorpius and Scutum. The eastern sky, however, is a virtual desert of bright stars. The Great Square of Pegasus has little to offer the naked eye observer, and Equuleus is likewise dim. On nights when a bright Moon floods the heavens with its golden light, the eastern sky appears almost devoid of stars. Near the meridian, however, in the small constellation of Delphinus the Dolphin.

pp 187

I can almost imagine Scotty setiing up at sunset, his charts in one hand, his tobacco pipe in the other, pensive, waiting for the curtain of darkness to draw on the landscape. August is a very special time in my own seasonal viewing, as it represents the end of a long period of summer twilight, when the sky never becomes truly dark. Running from late May to the end of July, year in, year out, the arrival of true darkness in early August is an event to be celebrated!

As Scotty mentions, the summer months generally bring the best seeing in the year, and that’s true across many areas of Europe too, despite the encroach of biting insects; Scotty had the mosquito, here it is the midge fly. Despite its diminutive size, Delphinus offers a fair amount of deep sky real estate for the enthusiastic star gazer and Scotty does a sterling job highlighting them for his readership.

Scotty says that he developed a “fondness” for Delphinus because of its richness in variable stars, which he enthusiastically monitored in the early days of his work for the AAVSO. On page 188 he points out that the constellation is home to a number of very fetching double stars that are accessible with binoculars or a small telescope. Arguably the most celebrated is Gamma Delphini, which marks the northeastern corner of the Dolphin. Through my 80mm f/5 achromatic telescope it is easily resolved at 50x showing a lovely golden primary and pale yellow secondary separated by about 12″ of dark sky.  Scotty says they’ve hardly moved since the system was first surveyed in 1830 by Wilhelm Struve.

Houston also mentions the much more challenging binary system; Beta Delphini ( magnitudes 4.0 and 4.9)  the secondary of which exhibits an apastron of 0.6″ and periastron of 0.2.” This system was first discovered by S.W Burnham in August 1873 using his 6 inch Clark refractor. Scotty informs us that Burnham was lucky enough to examine the stars near their maximum separation. Then on page 189 he delivers another invaluable account of his own efforts to resolve this pair using his old Newtonian;

In 1950 I examined the star with my newly completed 10 inch reflector. Then the separation was near a maximum of 0.6″ with the companion due north of the primary. My first attempts to split the pair failed because the companion was lost in the diffraction spike caused by the telescope’s secondary mirror holder. Success came only after rotating the tube 45 degrees in its cradle to shift the position of the spike.

pp 189.

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Author’s note: I have spent the past few years carefully studying the properties of Newtonian reflectors in regard to their ability to split double stars. My findings showed that they were excellent instruments in pursuing this high resolution work, which has been traditionally associated with equatorially mounted classical refractors, and more recently in the promotion of very expensive apochromatic refractors. My own instrument of choice in the divination of difficult double stars, including sub arc second pairs is a 20.4cm f/6 Dobsonian (affectionately called ‘Octavius’) with a 22 per cent central obstruction. This work has instilled in me a deep respect for these telescopes that I am eager to share with my peers across the world. I give thanks both to Scotty and to Stephen James O’ Meara for including this material from his old Sky & Telescope columns and this book, respectively.

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Octavius; the author’s tried and trusted 8″ f/6 Newtonian on its ‘pushto’ mount.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Delphinus is also home to a number of rather lacklustre deep space objects. A challenge for larger apertures is provided with the tiny, compact globular cluster NGC 7006 (magnitude10.5), found by panning some 3.5 degrees east of Gamma Delphini. In my 8 inch telescope, NGC 7006 remains unresolved at 200x; more like a fuzzy snowball than anything else. Indeed, Scotty maintains that it remains unresolved in all but the largest instruments, and I would tend to agree. The reason is the enormous distance of this globular; now estimated to be about 140,000 light years (Scotty quotes 110,000 light years).

In the last couple of pages, Houston  discusses a few other objects of note in Delphinus, including the globular cluster, NGC 6934, the planetary nebula, NGC 6905, and the galaxy, NGC 6956. What is noteworthy is that Scotty weaves the experiences of other observers into his narrative, including Barbara Wilson, Philip Harrington, as well as celebrated authorities from yesteryear, such as the Reverend T.W. Webb (see pages 190 through 191).

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Chapter 9: September

Scotty begins this month’s adventures in the oft overlooked constellation of Lacerta, the Lizard. Sandwiched between the larger constellations of Cynus to its west and Pegasus to its east, Lacerta is one of the ‘new’ constellations introduced by Johannes Hevelius in 1687. Scotty suggests we shouldn’t overlook Lacerta owing to the fact that since 1910, three novae have blazed forth from within its borders, so who knows when the next one will come.  First up, Scotty draws our attention a very picturesque open cluster of stars for binoculars or small telescopes; NGC 7243. You’ll find this cluster a little over 2.5 degrees west of Lacerta’s brightest luminary, Alpha Lacertae. Here’s how Scotty describes this cluster:

The cluster stands out especially well from the stellar background when I stop down my 4 inch Clark refractor down to 1.8 inches. According to Revue de constellations by R. Sagot and Jean Texereau, NGC 7243 in a 4 inch at about 50x is a rich traingular cluster of many stars between 9th and 11 th magnitude. The number of stars increases from about 15 in a 2 inch to 60 in an 8 inch. I found no define shape in a 12 inch recently, but counted at least 80 stars within a 1/3 of a degree area. Look for a wide double at the luster’s center, particularly if you have a 6 inch or larger telescope.

pp 197.

The surprisingly rich open cluster, NGC 7243, in Lacerta.

 

 

Author’s note: This cluster is indeed a fine sight in 15 x 70 binoculars or a small telescope. My 80mm f/5 telescope reveals about 30 members at 50x, but nearly double that in my 8 inch reflector. Larger telescopes show more, growing to well over 100 in a 12 inch instrument, though the precise number also depends on the magnifications employed. Best to experiment with NGC 7243 to see what’s what.

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4 degrees directly south of NGC 7243 is NGC 7209, described on the bottom of page 197 and 198.

At midnorthern latitudes, the grand constellation of Cygnus rises high in the sky for exploration during September. On pages 200 to 210, Twinky covers much of its rich cache of deep sky treasures. After providing some interesting background on the constellation, Scotty launches into a wonderful discussion on the North American Nebula (NGC 7000), an enormous emission nebula located about three degrees east of the bright summer star, Deneb.

The huge and sprawling North American Nebula ( NGC 7000); a visble and infrared presentation. Image credit: Wiki Commons.

 

 

From my location, the skies are just dark enough to enable me to see the brightest parts of this emission nebula without the aid of a nebular filter. With a 32mm Plossl eyepiece delivering the large true field possible with a 1.25″ ocular, my 80mmf/5 achromatic delivers a wonderful field some 4 degrees wide at 13x. Scotty points out that NGC 7000 is an object celebrated more in modern times than in the past (see page 202). He attributes this to the rather restricted fields of the best telescopes of yesteryear, which tended to have very long focal lengths and the relative paucity of good, wide angle eyepieces. Indeed, in the darkest skies that Britain can offer, you can indeed make out the North American Nebula with the naked eye. Indeed, I last observed NGC 7000 in August of 2016 during a trip to the remote island of Skye, off the northwest coast of Scotland.

From here, Scotty moves on to M39, a nice open cluster for binoculars or small telescopes right up at the northern end of the constellation. To see it, centre your telescope on 4th magnitude, Rho Cygni, and move a little under 3 degrees further north, where it will appear in your low power telescopic field. Covering an area about half a degree wide, my tiny 3.1 glass at 13x reveals about twenty members, scattered haphazardly across the field. Scotty says he noticed a dark streak running about 5 dgrees east southeastward  from M39. A dark dust lane? What do you think?

Messier 39 in northern Cygnus; a nice binocular and/or small telescope object.Image credit:Wiki Commons.

In discussing dark lanes and nebulosity, Scotty mentions something very curious at the top of page 203:

The detection of dark nebulosity depends on many factors. I lean toward using long focus instruments because my experience has shown that they tend to scatter less light and provide a higher contrast image than do rich field telescopes. I have had some dramatic views of dark objects with my old 10 inch f/8.5 Newtonian reflector and the 12 inch f/17 Porter turret telescope in Springfield, Vermont.

pp 203.

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Author’s note: If you actually read through the book, you’ll notice that Scotty also makes the same claims for the images served up by his 4″ f/15 Clark refractor.The common denominator, so far as I can see, is the long native focal length of both his aforementioned  reflecting telescope and the classical achromat. Cassegrain and compound (catadioptric) telescopes don’t really count, as the primary mirrors are quite fast (typically  f/2 to f/4). The latter’s high net f ratio relies on the magnifying effects of the secondary mirrors.

What do you think?

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Pages 204 through 208 covers the weird and wonderful Veil Nebula in Cygus, an ancient supernova remnant which occured 15,000 years ago. Scotty describes it thus:

…..a broken bubble of luminous gas some 2 degrees in diameter. Although ignored by generations of telescope users, in the past 30 years the veil has progressed from a difficult test object to a reasonable target for anything from binoculars to the largest amateur telescopes. It is an excellent nebula for trainig the eye, perhaps the most important observing ” accessory,” to help us get the most out of the telescope we are using.

pp 205

Scotty informs us that the brightest parts of the nebula were discovered by Sir William Herschel back in 1784 during one of his sweeps using his homemade 18.25 inch speculum.  The Veil is partitioned into two distinct regions, east and west, with the former (NGC 6992) being slightly more easy to see. The eastern Veil (NGC 6992 & 6995) is found about 2.7 degrees northeast of the star 52 Cygni (an excellent colour constrast double for small telescopes). The western segment (NGC 6960) can be detected snaking its way past 52 Cygni. Getting to the spot in the sky where the Veil is located is the easy part but seeing it is quite a different matter! You’ll need very dark and transparent skies to have the best chance of seeing it with a backyard ‘scope without a nebular filter.

On page 206 Scotty raises the very interesting observation that it was hardly mentioned by the great amateur astronomers of the 19th century, even though their telescopes were certainly capable of detecting it.

Your chances of seeing the Veil nebula increase dramatically as the aperture of your telescope increases, but you can get very good results using an 8 or 10 inch telescope and a OIII filter. To see the individual strands with the structure a medium power should be selected (80x or 100x works well). Filters can work with smaller telescopes too, provided the magnification is not pushed too high. Below is a sketch I made a few years back of the eastern Veil using my 80mm f/5 achromat at 20x,with a 1.25″ OIII filter attached.

NGC 6992/95 as sketched with a 80mm f/5 refractor, x 20 & OIII filter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Though he doesn’t mention them much, Houston describes his 5 inch binoculars on page 208. Earlier in the text, he does say that they were hobbled together from two Apogee 5 inch x 20 richfield refractors:

My Japanese 5 inch binoculars, though very heavy, originally had only a shaky tripod. I remounted them on a 3 inch pipe held in concrete down to the bedrock that is Connecticut. A well greased flange allows motion in azimuth while the altitude motion is provided by the binoculars’ built in trunions. Though makeshift, the mounting is granite steady and turns smoothly.

pp 208

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Author’s note: This is ‘vintage’ Scotty; making do with simple, no frills setups to maximise the time spent observing! Inspirational or what!

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On pages 208 through 210, Scotty shifts gear and dicusses the curious case of NGC 6811, a small open cluster located just under 3 degrees northwest of the challenging double star, Delta Cygni. Though his own notes recorded it as rather lacklustre; he received a curious letter from an amateur based in Denmark;

Several years ago I received a letter from Tommy Christensen, who lived in Odensa, Denmark, and observes with a 3.5 inch refractor. Along with a description of M33 and the Veil Nebula was a brief note about the open star cluster NGC 6811 in Cygnus. He called it one of the most beautiful clusters he had seen and mentioned a ‘ dark band about 5’ thick running through the middle of the cluster, not completely without stars, but nevertheless conspicuously dark.”

pp 209.

Scotty solicited comments from his army of fans, deliberately keeping his question about NGC 6811 vague.  Some of the responses he got were hilarious (you can read them for yourself on page 209), but quite a few folk did notice such a dark lane.

His conclusion was right on the money though:

This is a beautiful, albeit minor example of how people see things differently. Everyone was looking at the same cluster, but because of experience, conviction, or psychological factors, each saw it in a different way.

pp 209

The remainder of this chapter covering the September sky is devoted to Aquila, the celestial Eagle. On page 213, Scotty mentions our very own Rob Moseley (who kindly chimed in to this website a while back confirming the prowess of the Orion/Skywatcher 180 Maksutov in regard to its ability to resolve double stars) who wrote Scotty concerning the planetary nebula, NGC 6804;

One of the great pleasures of deep sky observing is the individuality that certain objects acquire in the eyepiece. I’m always delighted to learn that someone sees an object in a new perspective. One such example is Robert Moseley of Coventry, England, who tracked down NGC 6804 while testing a new 10 inch f/6 reflector. His best view was at 120x. He writes,” It gives the impression of a highly condensed but partially resolved cluster. It is a faintish oval nebulosity with a 12th magnitude star near its northeastern edge. With averted vision at least one other star could be seen superimposed upon it.” Moseley questioned the 13th magnitude I had given for NGC 6804 in an earlier column. Published magnitudes for planetary nebulae cause many disagreements, and I believe it is best to slightly mistrust all of them and to record your own magnitude estimates with your notes.

pp 213.

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Author’s note: Well done Rob! A fine addition to a fine book!

I like Scotty’s attitude to estimating magnitudes. What’s all the fuss about?

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Chapter 10: October

October is a most auspicious month for amateur astronomers. The summer haze and humidity have given way to cooler days and crisp, clear skies at night. darkness comes earlier, dewing of the telescope’s optics is generally less of a problem, and the sky is not do jammed with star clouds that confusion rules.

The Milky Way stretches from east to west across the northern star patterns, but here we are looking in the direction approximately away from the center of the galaxy. Star swarms marking the galaxy’s plane are thinner, and it is easy to star hop and make finder searches for objects embedded within them. Some of the most beautiful sights for small telescopes are in and around this corner of the Milky Way.

pp 217

October is indeed a wonderful month to be out of doors. The leaves of decidous trees shut down their chlorophyll factories, revealing the aureal tints of their secondary pigments. Nights are pleasantly long and temperatures remain mild for the most part. The great Square of Pegasus and Andromeda, the Chained Lady, loom large nearly overhead, ripe for exploration with binoculars and telescopes. And it is here that Scotty begins his adventures.

Beginning with the Square of Pegasus itself, Scotty asks a simple question requiring nothing from his readers except their naked eyes. How many stars can you count within the confines of the Square?

If you can see 13 you are reaching magnitude six.

pp 218

On the next page he follows this up with another question. How many deep sky objects are visible in Pegasus? The answer to this question depends on how acute your vision is but also on the size of the telescope you observe with. And it is here that Scotty reflects on the growth of telescopic aperture in comparison to earlier times:

Telescopes of 17 inch aperture are now off the shelf items of modest cost. There are a dozen or more amateur groups in the United States that either now have or are completing instruments with apertures of 24 inches or more. Such light gathering power brings within reach of the backyard observer virtually every deep sky object in the NGC and IC compilations. Thus the Great Square of Pegasus alone contains more than 100 suitable objects.

pp 219

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Author’s note: Scotty is referring here to the Dobsonian Revolution that swept the amateur world by storm in the last quarter of the 20th century. The Newtonian reigns supreme! As I explained in my book, Choosing and Using a Dobsonian Telescope, this was a true revolution and the only one that has occurred in amateur astronomy in living memory. And it’s gone from strength to strength; now amateurs are using fast 30 inch + behemoths for very reasonable cash investments, and which breakdown into convenient packages that can fit in an average sized car.

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The first deep sky object visited is 12th magnitude NGC 7479, found by panning just shy of 3 degrees due south of Alpha Pegasi, which marks the southwestern (Scotty mistakenly quotes southeastern pp 219) corner of the square;

The magnificent barred spiral galaxy, NGC 7479 in Pegasus. Image credit: ESA/NASA

If your eye is properly dark adapted, the galaxy should be visible in even a 3 inch telescope, but a 6 inch is better. A cloth over your head and the eyepiece gives you good protection from stray light. I have seen it easily with my 4 inch Clark refractor, but with small an instrument it is not possible to see any detail. On the otherhand the 12 inch f/17 Porter turret telescope at Stellafane in Springfield, Vermont, offers a more interesting view. At 300x the central bar is obvious and there is a hint of a spiral arm at one end.

pp 219/20

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Author’s note: My 8 inch reflector at 60x can make out the galaxy’s bright core, but the spiral arms do not yield at any power. Caldwell 44 needs a big gun to do it justice!

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Time and time again, Scotty affirms that high f ratio ‘scopes appear to do better than those of low f ratio, but is careful not to jump to any firm conclusions;

A 12 inch f/5 reflector set up near the Porter telescope did not offer as good a view of NGC 7479 even though I thought the mirror was good.It may have something to do with the longer focal length of the Porter telescope, or a better eyepiece. The importance of fine quality eyepieces has been overlooked by many amateurs…..Objects once considered only within reach of large amateur instruments are being seen in smaller telescopes equipped with fine eyepieces.

pp 220

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Author’s note: This is a can of worms! Don’t go there Scotty!

Longer focal length mirrors have less geometrical aberrations than their shorter focal length counterparts. That’s why we have coma correctors, for example! The former also hold their collimation better. That’s one of the principal reasons why I have called for the introduction of a mass market 8 or 10 inch f/7 Newtonian. Eyepiece quality is important too, as Houston points out. But we live in wonderful times nowadays. Eyepieces of higher quality than arguably the best in Scotty’s day are now available at very reasonable prices.

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On pages 222 through 226, Scotty sojourns to two celebrated globular clusters adorning the autumn sky; Messier 15 in Pegasus and Messier 2 down in Aquarius.

Messier 15 as imaged by the Hubble Space Telescope. Image credit: Wiki Commons.

M 15 is easy to find about 4 degrees northwest of Epsilon Pegasi. At magnitude 6.3 it’s just within the visual range, provided you have keen eyesight and observe under a dark, country sky. The finder view is very distinctive, as the globular sits a mere half a Moon diameter due west of the magnitude 6.1 star. It pays to study the field at low power. Both objects are of the 6th magnitude but that of the globular is integrated, while that of the star is a point source. This is a good place to learn the difference between the two concepts.

The view of M15 is impressive with anything from binoculars to the largest telescope. telescopes of 4 inch aperture and lesswill not resolve the core of M15. My 4 inch Clark refractor at 40x shows M15 as a slightly oval disk, more luminous in the center, with edges just beginning to break up into individual stars. Increasing the magnification enhances the view, and at 200x stars at the center of the cluster star to be resolved.

pp 223.

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Author’s note: M15 is a beautiful object at 150x in my 8 inch f/6 reflector. If you have a telescope of 12 inches or larger, M15 presents an extra challenge for you. Located in the northeast corner of the cluster is the 14th magnitude planetary nebula, Pease 1 (mentioned by Scotty on page 224). This was the first planetary to be found within a globular cluster. It was discovered in 1928 by Dr. Francis Gladheim using the 100 inch Hooker reflector atop Mount Wilson.

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Moving to the northern edge of Aquarius, the Water Bearer. You can track this magnitude 6.6 globular a little over 4 degrees north of Beta Aquarii. My 130mm f/5 reflector at 100x shows it be noticeably elliptical and more condensed than M 15 but still a fine sight nonetheless. Scotty writes some interesting notes on M2:

The famous variable starobserver and comet discoverer Leslie Peltier finds M2 a more difficult object for the unaided eye than M33, the large spiral galaxy in Triangulum. In the clear dark skies over the Yucatan peninsula in Central America I could view M33 directly, but M2 required averated vision before it could be glimpsed directly. But I have seen M2 often with the naked eye in Kansas, Missouri, Arizona, and even from the bayous of Louisiana. Binoculars give enough detail to keep the amateur interested, while the view I once had with the Wesleyan University’s 20 inch Clark refractor was spellbinding.

pp 225

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Author’s note: I would agree with Scotty that you’ll need a good 12 inch (see page 226) or larger telescope and high magnification to fully resolve this globular cluster

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As a child  I would stand outside on autumn evenings and fantasize about constellations. I would watch as the horse archer Sagittarius shot a golden arrow at Scutum( Sobieski’s Shield). The arrow would strike the top of the shiled, tearing a great hole in it, and the fragments would fall back together as the arrow shaped open cluster M1.  The arrow would then soar upward into the star clouds, where it would hang poised for another  target in the Milky Way or perhaps another galaxy or even some imaginary other universe.

pp 226

With beguiling prose like this, Scotty would set his readers reeling for crystal clear skies. This is how he introduces his next object, the globular cluster, M71 in the peitite constellation of Sagitta, the Celestial Arrow, easily found immediately north of Aquila. Scotty says he first spied this 8th magnitude cluster with his 40x spyglass of 1 inch aperture. You can pick M71 fairly easily as it lies about midway between the third magnitude luminaries, Delta and Gamma Sagittae.

My 130mm f/5 reflector at 123x shows up a suprising number of stars (about two dozen) in this globular in a pretty stellar hinterland. Indeed, one can be fooled into thinking M71 is a dense open cluster rather than a bona fide globular. Scotty provides us with these notes;

My old 10 inch f/8.6 reflector, which, with its 0.75 inch thick plate glass mirror, was essentially a forerunner of today’s Dobsonians, gave a magnificent view of M71 at 100x. Stars were visible across the entire disk, and the object looked decidely like  an open clusterThe 20 inch Clark at Wesleyan University’s Van Vleck Observatory in Connecticut shows something  more globular.

pp 228

On pages 230 though 232 Houston discusses the celebrated Helix Nebula (NGC 7293) in Aquarius. In his discourse, Scotty includes the descriptions provided by dozens of observers using all manner of telescopic aids and is well worth a read.

On page 234, Twinky discloses a wonderful snippet of American astronomical history:

After the U.S. Civil War, however, Americans went on an observatory building binge. Funding for many installions came from state legislatures, since the astronomers provided time signals to their local areas. Almost every observatory from that era had a transit instrument for determining time. In return for their service, the lawmakers funded a large telescope to keep the astronomers happy. When I was at the University of Wisconsin in the 1930s, Wasburn Observatory still had the big brass fittings on the control board that routed time signals to commercial customers…. Most American observatories did not have special programs to search for deep sky objects.

pp 234

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Author’s note: As explained in my book, Choosing and Using a Refracting Telescope, the largest equatorially mounted telescope in the United States in 1830 was a 5 inch Dollond refractor. Henry Fitz  is reputed to have made about half of all the telescopes sold in America between 1840 and 1855. Soon other makers of renown were establishing themselves, including  Alvan Clark & Sons and John Brashear, who improved and continued this telescope making legacy for the next 80 years or so. The great classical refractors, erected in their ‘cathedrals’ dedicated to the heavens, were symbolic of the new scientific confidence that the United States would enjoy well into the 20th century.

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The final pages of this month’s chapter (236 through 238) discuss a number of deep sky objects south of Fomalhaut, many of which were discovered by Sir John Herschel from his observing station at the Cape of Good Hope, South Arica.

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Chapter 11: November

We’re now approaching the end of the observer’s year but that certainly doesn’t mean there will be any let up in the convoy of celestial treasures to be enjoyed. In many ways, Scotty leaves the best until last, exploring as he does the bountiful constellations of Cassiopeia, and Andromeda riding high in November skies, as well as venturing to more southerly destinations in Pisces and Sculptor.

Scotty gets us off to a flying start by exploring a number of beautiful open clusters in Cassiopeia, the Celestial Queen, including NGC 457, NGC 436 and the visually striking NGC 7789.

The beautiful and exceedingly rich open cluster, NGC 7789, in Cassiopeia. Image credit: Hew Holooks.

 

 

 

 

 

 

 

 

 

 

 

No treatise on deep sky observing could fail to ignore NGC 7789, found about halfway between Rho and Sigma Cassiopeiae. Discovered by Caroline Herschel back in 1783, my 130mm f/5 reflector frames the cluster beautifully at 85x, revealing at least three score stars spalshed across an area roughly one quarter the size of the full Moon, and the 8 inch pulls in more than 100 at moderate powers! Scotty doesn’t hold back describing the splendour of this rich galactic cluster 6,000 light years away from the solar system;

NGC 7789 is one of those rare objects that is impressive in any size instrument. With a 4 inch rich field telescope the cluster appears  as a soft glow nearly 0.5 degrees across and speckled with tiny, often elusive, individual stars. the 12 inch f/17 Porter turret telescope at Stellafane picks up more than 100 stars. Through a 16 inch aperture the view is spectacular, and the whole field is scattered with diamond dust. And a 22 inch Dobsonian reflector in the clear skies of california gave a most impressive view with countless sparkling points filling an entire 60x field. I particularly like the drawing made by [Admiral W.H] Smyth with a 6 inch refractor.

pp 243

Another object of note in these pages is M 52. To find this 7th magnitude cluster, consider an imaginary line running from Shedir to Caph. Now extend this line about the same distance again until your finder picks up a roughly kidney shaped foggy patch of light a little less than half the size of the full Moon in diameter.

M52 ; a fine open cluster for small telescopes in Cassiopeia. Image credit: Wiki Commons.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

November is a great month for observing the Andromeda Galaxy (M31), easily found with the naked eye from a fairly dark site a few degrees about Mirach (Beta Andromedae).  Large binoculars can often provide the best views of this enormous spiral galaxy on our doorstep but I am also very pleased with the view served up by my 80mm f/5 refractor coupled to a 32mm Plossl delivering 13x. It shows a very bright nucleus which gradually fades on either side. Just how far one can trace the spiral arms of M31 depends on a number of factors, not least of which is telescopic aperture, visual acuity, sky darkness and transparency. Most backyard ‘scopes can trace them to maybe 3 degrees from end to end, but Scotty informs his readers on page 246 that George P. Bond, employing the 15 inch refractor at Harvard College Observatory was able to follow the spiral arms out to 4 degrees as far back as 1847. Yet, in 1953, Robert Jonckheere, using ordinary 50mm binoculars measured their visble length to be 5.17 angular degrees!  Scotty recommends moving the nucleus out of the field to have the best chance of tracing these spiral arms. Indeed, he claims that after using 15 x 75 binoculars, he was able to measure a length of 5 degrees from end to end!

The great Spiral Galaxy in Andromeda seen here with its bright satellite galaxies, M32 left and M110 ( below to the right of centre). Image credit: Torben Hansen.

 

 

 

 

 

 

 

 

 

 

 

The two bright satellite galaxies attend M31, both of which are easily discerned in my 80mm refractor at the lowest power. M32 lies closer to the core of M31, whilst M110 is located further away ‘below’ the disc of M31. Scotty also reminds his readers that two other companion galaxies can be ferreted out some 7 degrees north of M31; NGC 147 and NGC 185. NGC 147 (actually located over the border in Cassiopeia)., which shines with an integrated magnitude of 9.5 can be found just under 2 angular degrees west of Omicron Cassiopeiae. The other galaxy, NGC 185, is slightly brighter, owing to its smaller, more compact size. It lies just one degree east of NGC 147. Both are well framed in my 8 inch reflector at 30x.

Scotty then moves down to Pisces, to visit the grand face on spiral galaxy, M 74. This magnitude 9.2 gem is easily located in my 80mm refractor by centering the 3rd magnitude Eta Piscium in a low power field. The galaxy is then seen as a ‘fuzzy star’ about 1.3 degrees off to the east and slightly to the north of Eta. You need a larger telescope to make out the spiral nature of this galaxy though. My 8 inch at 150x shows a number of faint stars splashed around its periphery and with good transparency, you’ll be able to make out something of its spiral nature but not a great deal. In general, it’s best to use the largest telescope available to engage in this kind of work.

After discussing some less well known faint fuzzies in Pisces, Scotty finally moves into Sculptor, featuring some of the observations of Ron Morales, Barbara Wilson and Steve Coe.

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Chapter 12: December

The stuff dreams are made of; the Pleiades Cluster in Taurus, with its associated nebulosity. Image credit; Wiki Commons.

December brings winter, and with it many cold but often clear nights. On such evenings, when the stars sparkle like diamonds, there is no sight as spectacular as M45, the Pleiades. Currently, this open star cluster rides high in the eastern sky at the end of astronomical twilight. It is delightful in any instrument, from the naked eye to the largest amateur instrument, although I find large binoculars give the most impressive view. Almost every culture, past and present, mentions in its folklore the dazzling stars in this nearby culture. They have enhanced the imaginations of gifted poet and commoner alike as far as we can remember. They are the starry seven of Keats, the fireflies tangled in a silver braid of Tennyson, the fire god’s flame of the old Hindus, and the ceremonial razor of old Japan. No other celestial configuration appears so often on the pages of the poet.

pp 261.

There can be few sights that move the human spirit more deeply than the sight of the Seven Sisters rising serenely in a dark country sky. The cruelty of winter frost temporarily abates, as the mind soars. Why is the night sky so beautiful? Why were the stars made? Different people have different answers to these questions but to me they plainly attest to a Creator who delights in fashioning beautiful things, and was gracious enough to place them in the firmament so that we might know something of His awesome power. Rich or poor, young or old, the Pleiades is for everyone.

Not surprisngly, Scotty has a lot to say about this magnificent star cluster. How many stars can you see within its confines? Most have no trouble making out six members. With a little practice, a seventh can be made out, but the keenest eyes report more, many more.

Depending on light pollution and sky conditions , most persons can see between four and six naked eye Pleiads.Traditionally, the average eye can see six stars here, the exceptional eye seven, and 10 bear names or Flamsteed numbers. However, during the 1800s the noted British amateurs Richard Carrington and William Denning both counted 14 stars. The late dean of visual observers, Leslie Peltier, told me he could always see 12 to 14 stars on any good moonless night.

pp 263.

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Author’s note: Having average eyesight, I can usually only count 6 members, but have certainly glimpsed a seventh but only in the darkest skies that Scotland can offer. If you have a good, blackened telescope tube (without its lenses) lying about, try peering through it to minimise the amount of peripheral light entering your eye. Can you see any more? Indeed, in perusing the work of the Victorian populariser of astronomy, Sir Robert Ball, I recall him stating that one could see stars during broad daylight if one were to observe from the bottom of a deep well. Alas, I can’t confirm this! 19th century skies were considerably darker than those we typically enjoy today, helping to explain why these observers of old saw so many more Pleiads than we generally can.

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On page 263 through 265, Houston discusses the nebulosity enveloping M45, itself a good sign that the cluster is relatively young ( of the order of a few tens of millions of years most likely). The area of sky around  the star Merope is usually the place where most amateurs report such nebulosity. Technically this is a reflection nebula, where the star light is insufficiently energetic to ionize the gas but enough to allow it to get scattered off innumerable dust grains within the cluster. It was first reported by the German amateur astronomer, Wilhelm Tempel, back in 1859 using a 4 inch Steinheil refractor whilst working in Italy. Scotty points out that seeing this nebulosity depends strongly on the conditions of the sky through which we observe;

From Tucson my 4 inch showed it readily. In Connecticut, a 10 inch reflector failed but in Vermont a 5 inch Moonwatch Apogee telescope succeeded. At the August convention of the Astronomical League in Tennessee, I was surprised to find several observers who had seen the Merope Nebula more than once. It was readily visible in a 6 inch reflector made by Fred Lossing of Ottawa. Once its position southwest of the star Merope was pointed out, others saw the dim glow too. In the 16 inch, the nebula seemed much more obvious, and averted vision was not required.

pp 263.

The Crab Nebula (M1) in Taurus. Image credit: Wiki Commons.

Of course, the Pleiades is grand star cluster within the larger constellation of Taurus, the Bull, and on page 265 Scotty discusses a few other gems that are visible within the constellation using the naked eye, binoculars or a modest telescope. The Hyades is a sight to behold with the naked eye or through low power binoculars or even opera glasses. Then there is the Crab Nebula (M1), which is best found by centering the star Zeta Tauri in the low power field of view of your telescope and then panning 1 degree to the northeast. The Crab is rather disappointing telescopically as it certainly does not resemble the images seen in long exposure photographs, and increasing aperture doesn’t greatly transform the view. Scotty agrees:

The Crab can be seen in 2 inch finders. Small telescopes reveal only a shapeless 8th magnitude blur variously sketched as oval, rectangular, or more often something in between.

pp 268

After discussing a few deep sky objects in Cetus, Scotty throws caution to the wind and encourages sky gazers to return to the easy objects that delighted us in our youth:

As many of us know, the telescope is a wondrous invention, and the heavens contain all manner of marvels that can still astound the imaginative mind, no matter what the smog density may be. Some of the better sights await us in the December evening sky. The Northern Cross is erect in the Northwest; Albireo has already set. Pegasus is now a great diamond shape sloping slowly to the west, as Orion mounts closer to the meridian. This is no time for routine or difficult objects; it is better that we sweep again the old favorites of our youth; the sights that enthralled us with our first homemade reflector.

pp 276

By now, old Twinky was already thinking about the great sights that he would revisit in the new year; the Great Nebula in Orion, Barnard’s Loop, the magnificent Double Cluster; and so it begins again!

Dr. Neil English’s new book, Tales from the Golden Age of Astronomy will be published in the Spring of 2018.

 

De Fideli.

Tales from the Golden Age: A Short Commentary on Walter Scott Houston’s,”Deep Sky Wonders.”

A Distillation of observing notes from the late Walter Scott Houston(1912–93).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Between 1946 and 1994, the noted American observer, Walter Scott Houston, wrote the Deep Sky Wonders column for Sky & Telescope magazine, entertaining several generations of amateur astronomers across the English speaking world. His great personal knowledge of the deep sky and enthusiasm to share his experiences were downright infectious. With beautiful prose and just the right amount of technical detail, Houston’s writings presented delightful ‘word pictures’ of the many deep sky objects that adorn the night sky. The present work, first published in 1999 by Sky Publishing Corporation, represents a distillation of his writings which appeared a few short years after his untimely passing in December 1993.

The copy of the book discussed here refers to the paperback edition (309 pages), containing a preface, followed by 12 chapters covering all the months of the year, and ending with source references, a bibliography and index. The selective writings are edited by the noted observer and former Sky & Telescope columnist, Stephen James O’ Meara.

The Preface

This is divided into three distinct sections with commentaries from O’ Meara, Brian Skiff and Dennis di Cicco, who provide interesting biographical details of Houston’s life and observing philosophy.

Born in Tippecanoe, Wisconsin, on May 30 1912, Houston developed an early interest in optical instruments, constructing his first telescope as a preteenage boy: a 1 inch aperture refractor from salvaged spectacle lenses, and mounted inside a cardboard tube, which provided a magnification of 40 diameters. But we also learn that ‘Scotty’ was far more knowledgeable about microscopes than telescopes. Growing up in an era where good telescopes were very expensive by modern standards, Houston, like so many of his contemporaries, resorted to grinding his own mirrors in order to sate his growing aperture fever. This resulted, we are further informed, in a badly made 6 inch primary mirror he finished in 1930, but it was soon improved upon when he apparently produced a first rate 10 inch silver on glass mirror which formed the heart of Houston’s first serious telescope, an instrument that consolidated his lifelong love for the treasures of the deep sky. The interested reader will note that Scotty’s 10 inch mirror is on display at the R.W. Porter Museum of Amateur Telescope Making, Springfield, Vermont.

After leaving school, Scotty studied for a degree in English literature at the University of Wisconsin and it was here that he made his acquaintance with a one Joseph Meek, who stoked his interest in observing variable stars. Indeed, after joining the American Association of Variable Star Observers (AAVSO) in 1931, he went on to contribute an astonishing 12,500 observations throughout his long life!

Scotty was quite the scholar, securing teaching positions at various public schools and universities across the American Midwest. During World War II, he served as an instructor for pilots at the Army Air Force’s Navigation School, at Selman, Louisiana. Finally, he moved to Connecticut, where his skills in the written word were put to good use as an editor for American Education Publications, a post he held until his retirement in 1974. He and his wife, Miriam, were inveterate travellers, visiting astronomical conventions and star parties across the United States, where he endeared himself to the community, which had so admired his Deep Sky Wonders column over the years and decades since its inception back in 1946.

Observations made with this homemade 10 inch f/8.6 reflector formed much of the basis of Scotty’s earliest astronomical forays, conducted under the dark skies of rural Kansas throughout the 1950s. That instrument must have been a best of a ‘scope, but it served as his workhorse for many years. Scotty was also very enthusiastic about using binoculars, as we shall discover. His association with the AAVSO introduced Houston to arguably his favourite telescope;a 4 inch f/15 Clark achromatic refractor. On page 84 of Deborah Warner’s book, Alvan Clark & Sons, Artists in Optics, we learn of more details about the instrument:

William Tyler Olcott, the author of several popular books on astronomy, used a 4 inch aperture Clark refractor made in 1893. A wooden tripod supported the brass with nickel tube and a hand driven work wheel. Olcott later gave the telescope to Phoebe Haas (q.v), who then gave it to the American Association of Variable Star Observers, which in turn loans it to its members. The Olcott instrument is now being used by Walter Scott Houston.

pp 84.

A neoclassical 4 inch f/15 refractor, similar to that used by Houston, and once used by this author for several years.

Later in his life, Houston acquired a 5 inch Apogee ‘Moonwatch’ rich field refractor delivering a fixed power of 20x, which he used to sweep the skies, and which features in many of his later monthly columns. He also had in his possession a 5 inch binocular, which is occasionally mentioned in the text.

Scotty eschewed the growing number of amateur astronomers who were becoming increasingly obsessed with their equipment. He was an observer, not a ‘gear head’. Brian Skiff explains:

Scotty had a light touch and avoided being distracted by technical details. You don’t find any invidious comparisons of different telescope or eyepiece brands in his writing or much about the nitty gritty of equipment at all, because Scotty knew that the most important piece of equipment was the eye, and its training the most important activity; all else was trivial in comparison. Time wasted arguing the virtues of one eyepiece over another was time not spent honing your observing skills.

xiv

How times have changed!

It was with this modest cache of instruments that Walter Scott Houston created his literary magic; word enchancements that we shall explore in this essay.

Houston invited many of his readers to comment on the more speculative commentaries he made in the course of making his observations, and accordingly invited them to write him with their findings. In this way, Houston built up a formidable correspondence base with fellow observers across the United States, Canada and further afield, and when he attended star parties he would get to finally meet his admirers in person. Back in those days before internet, Scotty corresponded with his fans via snail mail. Specifically, they’d receive a small blue postcard with a personalised message. In these and other ways, he endeared himself to his readers and inspired many to take up the gauntlet to explore the riches of the deep sky.

One of his greatest admirers was W. H. Levy, of comet fame. Indeed, according to Skiff, it was ‘Twinky’ (aka Houston), who provided the essential push to him becoming the celebrated comet discoverer he subsequently became:

David Levy tells the story of meeting Scotty at a Deep Sky Wonder Night in northern Vermont in late August 1966. He had just begun comet hunting some months earlier. In the middle of the night, David took a break and began telling Scotty of his hopes to discover a comet someday. Puffing slowly on his pipe, Scotty asked David what the sky was like outside. He answered that it was pretty clear, dark and moonless. Scotty then asked if David’s telescope was out there, to which the answer was “yes.” Scotty took another puff on his pipe, looked up quizzically and said, “Well, David, you sure aren’t going to find a comet as long as we’re inside talking about it!”

xiv

In 1980, Scotty underwent surgery to remove a cataract from his observing eye. As we shall see in his discourses, this greatly increased his sensitivity to shorter visual wavelengths as well as ultraviolet radiation. We will also discover a wealth of information concerning what ordinary individuals achieved using modest instruments, thereby providing yet more historically relevant documentation on what experienced individuals saw under the starry heavens. The individual chapters cover the entire observer’s year, parsing the sky up into twelve slices, with each fully two hours of right ascension in width. So, why not pull up a chair and enjoy some of the highlights of this charming and inspirational work from memory lane.

The Great Nebula in Orion, the majestic furnace of winter. Image credit Wiki Commons.

Chapter 1: January

I learned my constellations in Tippecanoe, Wisconsin, a town that long ago vanished into the urban sprawl of Milwaukee. Back then Tippecanoe was a rather treeless tract of farmland bounded by the great clay buffs of western Lake Michigan. The sky ran right down to the horizon, with an almost irresistible force, called for you to look at it. In January 1926, after a midnight walk home from ice skating, I wrote:

Snow crystals like blue diamonds, but with a dreamy gentle radiance totally unlike the harsh gem. A rail fence as black as Pluto himself runs along the road. The forest is black in the distance. The landscape is a masterpiece in ultramarine and sable.

As if in contrast, the heavens above blaze with a thousand tints. Incomparable Orion leads the hosts with blue Rigel, ruby Betelgeuse, and bright Bellatrix. His silver belt and sword flash like burnished stellar steel. And more advanced is the dark and somber Aldebaran, so heavy and gloomy. In fitting contrast are the delicate Pleiades, who sparkle “like a swarm of fireflies tangled in a silver braid.”

How can a person ever forget the scene, the glory of a thousand stars in a thousand hues, the radiant heavens and the peaceful Earth? There is nothing else like it. It may well be beauty in its purest form.

pp 1/2

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Author’s note:  Few books make an entrance like Scotty’s opening lines of chapter 1. Recalling the days of his youth, when the skies near his home were sublimely dark and crystal clear, and when light pollution was simply non existent, Houston thrusts us headlong into the starry universe of a freezing January night. Such a scene reminds this author of the sable skies of his own youth, when he’d sit on his back on a windswept sand dune on the south coast of Ireland during summer holidays, where the stars, too numerous to count, would stretch all the way down to the horizon! The brilliant luminaries of January, coupled to the naturally darker sky experienced as our planet faces away from the hustle and bustle of the down town Milky Way, would have certainly bewitched the young sky gazer and instilled in him/her a great yearning to explore its cavernous reaches with optical aid.

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On page 2 through 5, Scotty introduces us to the glories of the Great Nebula in Orion, a most fitting place to start Deep Sky Wonders. He describes how the nebula was first ‘discovered’ in 1611 and informs us that Sir William Herschel turned his first homemade reflecting telescope toward it in 1774 in the aftermath of some two hundred failed attempts to fashion a decent speculum mirror! Scotty’s mind wanders, as he discusses the drawings made of the Orion Nebula by telescopic observers prior to the advent of astronomical photography;

Drawings of the Orion Nebula made before the influence of photography raise more questions than they answer. Only superficially do the sketches bear any resemblance  to one another. The bright section of the nebula drawn by Bindon Stoney using Lord Rosse’s 3 foot reflector in Ireland doesn’t begin to match what I saw in 1935 with the 36 inch reflector at Steward Observatory in Arizona. Trouvelot’s 1882 lithograph based on observations with the Harvard 15 inch is a reasonable match to my view through a 3 inch. On the other hand, John Mallas’ drawing in the Messier Album, made in the 1960s with a 4 inch telescope shows features that most observers need a 10 inch to see.

pp 4

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Author’s note: It is difficult to see the precise point Scotty is making here. Certainly, the visual acuity of the observer has a role to play, and it is certainly true that a good observer with a small telescope will probably see more than a poor observer using a larger instrument. Nevertheless, it is undoubtedly true that for observing the Orion Nebula (or, indeed, the vast majority deep sky objects) that a good observer will see more in a larger instrument than the same individual will see in a smaller one, provided the optics are working as they ought to.

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The Nebula, as Scotty ably reminds us, responds well to all magnifications. “Its chaotic form gives a strong impression of twisting and turbulent motion,” he writes, “that are too slow to follow….. and its green tint is obvious to most. …… With low powers and a field wide enough to include the whole nebula, it becomes an object compelling enough to draw exclamations of delight from even the most disinterested bystander.”

pp 5.

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Author’s note: Scotty is dead right! Seeing the Orion Nebula through most any telescope, large or small, is sure to knock your socks off and is arguably one of the best outreach objects to enthral beginning observers.

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On pages 5 through 6, Scotty discusses the elusive Barnard’s Loop, an enormous, faint emission nebula running for several tens of degrees east of the Orion’s belt asterism.  He informs us that E.E. Barnard did not, in fact, discover the structure. It was the harvard astronomer, W. H. Pickering who first picked it up on photographic plates made at Mount Wilson in 1889; a full five years before Barnard’s own wide field astrographs confirmed it.

The beautiful but visually challenging Barnard’s Loop in Orion. Image credit: WIki Commons.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In all his years of searching with instruments of all shapes and sizes, Houston admits that the structure had eluded him, until one night at his Connecticut home, he saw it with his naked eye when he placed a OIII filter up to his eye! The sighting of it drove him wild:

My wife says I jumped clean over the observatory (it’s a small building).

pp 6

Sticking with elusive objects, Scotty then moves onto the Horsehead Nebula, which, although discovered photographically in 1900, had eluded the most seasoned deep sky observers for generations. It’s found very close to 2nd magnitude star, Alnitak, the southermost luminary in the Hunter’s belt. Even to this day, the Horsehead has evaded most deep sky observers, generally requiring large aperture telescopes and excellent seeing conditions. A Hydrogen beta filter (unavailiable in Scotty’s time) also helps make this nebula pop.

Scotty provides his own findings with the Horsehead:

From Connecticut my 4 inch refractor failed to reveal the Horsehead, but my notebook indicates that it was visible from Kansas with a 10 inch reflector. I have since fished it out using a 4 inch Clark, a 4 inch off axis Newtonian telescope made by Margaret Snow, a 5 inch Moonwatch Apogee telescope under the same circumstances as Mr. Wooten, immediately after the passage of a cold front.Scattered light from 2nd magnitude zeta foils many attempts to find the Horsehead, since the two are seaprated by only 1/2 a degree.

pp 8

Less challenging is the Flame Nebula (IC 434), located a mere 15 arc minutes to the southeast of Alnitak. Scotty reports that the Flame has been observed in instruments as various as a 60mm classic refractor as well as small reflecting telescopes. Scotty received reports that the Flame was exceptionally well observed at high altitude.

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Author’s note: Many years ago, during my brief forays into astrophography, I captured a reasonable image of the Horsehead and Flame Nebula using a 8 inch Schmidt Cassegrain telescope on Kodak ektachrome. Visually, it remains an elusive object to my eyes. The Flame Nebula can be glimpsed at powers of about 200x in a good 8 inch reflector and of course, one should not neglect Alnitak itself, which presents as a wonderful triple star for backyard telescopes.

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Scotty made it very clear from his writings and correspondences with amateurs across the country that the sighting of many deep sky objects depend more on the condition of the sky from which it is observed than the visual acuity of the individual. This is brought into sharp focus whilst discussing his next January target, M33, the Pinwheel Galaxy in Triangulum, which is presented on pages 9 through 11. Good seeing conditions and clean air swept clear of particulates render M 33 visible without optical aid. Scotty also informs us that it can prove a difficult target to pin down telescopically, owing to its low surface brightness:

With a diameter of 1 degree, the 7th magnitude spiral more than fills the field of view in high power binoculars and presents an almost featureless glow that is easily missed. Therefore, very low powers or even small binoculars give the best view.

pp 10.

The Pinwheel Galaxy, as imaged in a 10 inch Newtonian reflector. Image credit: Alexander Meleg.

With careful study in a moderatey large back yard telescope, Scotty  says;

“M 33 is usually smooth, but on one night I saw the whole surface surprisingly mottled, with the southeast part considerably brighter than the northeast….. Most observers settle for for locating NGC 604, a bright knot in one arm 9.1′ east and 7.6′ north of the galaxy’s nucleus….. One night in an 8 inch, a congested mass of bright patches was seen superimposed on an overall spiral pattern.

pp 11

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Author’s note: The Pinwheel is a fascinating object to study in telescopes of 8 inches or larger aperture. It is very well presented in my 8 inch reflector at 30x, where a roughly ‘S’ shaped structure is seen snaking its way from a slightly brighter and more condensed centre. If you crank up the power to over 100x or so, one can make out NGC 604 as a distinct blob at the extreme tip of the galaxy’s northern spiral arm.

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On pages 11 through 15, Scotty fleshes out details of an interesting correspondence with a one Pat Brennan, of Regina, Saskatchewan, an avid deep sky obsever who used a homemade 6 inch f/7 Newtonian to carry out his own observations of more obscure NGC objects and who was struck by the disprepancy between their description in Dreyer’s New General Catalogue (and its revisions) and how he found them at the eyepiece. As Scotty points out, the all sky photographic surveys, recording as they do a bewildering number of faint and bright objects, would often overwhelm well defined clusters as seen in a small amateur telescope. A few such objects (loose open clusters) are discussed, including NGC 1662, NGC 2180 and NGC 2184 in Orion, NGC 2251 in neighbouring Monoceros and NGC 7394 in Lacerta. The moral of the story here is that until one actually observes such systems for oneself, descriptions can be next to meaningless.

The magnificent Double Cluster (Caldwell 14) in Perseus.

 

 

 

 

 

 

 

 

 

On pages 16 through 19, Scotty discusses one the most beautiful deep sky treasures in all the heavens, the celebrated Double Cluster (also known as Xi Persei) in the constellation of Perseus. Although known to the ancients, the Double Cluster’s true majesty could scarcely be revealed until the age of the telescope was upon us. And while anyone evenly briefly acquainted with the night sky can find it without much trouble with the naked eye, Scotty is nonetheless careful to provide his readers with good directions on how to find it from less than ideal skies.

Scotty reveals that many of the great telescopic observers of past centuries recognised its splendour, including W.H. Smyth, T.W Webb and W.T. Olcott. Serviss’ Astronomy with an Opera Glass, published in 1888, described it thus:

With a telescope of medium power, it is one of the most marvelously beautiful objects in the sky; a double swarm of stars, bright enough to be clearly distinguished from one another, and yet so numerous as to to dazzle the eye with their lively beam.

pp18.

A composite drawing of the Double Cluster by the author conducted with a 32mm Plossl coupled to an 18cm f/15 Maksutov Cassegrain.

Houston provides his readers with some historical references to observers who first coined the term ‘Double Cluster’, with a number of individuals using the phrase beginning around the latter part of the 19th century. From here, Scotty wastes no time in providing his impression of the system as seen through a medium sized telescope:

Each of these two open clusters would stand well on their own , but they are even more spectacular because, less than a degree apart, they are visisble in the same low power field. I see h Persei (NGC 869) being slightly brighter and more concentrated of the two. Becvar’s Atalas catalogie gives the star count in NGC 869 as 250. Just 1/2  a degree east, Chi Persei is said to contain some 300 stars. However, anyone who looks with a 10 inch telescope will certainly consider the catalog values to be conservative.

pp 19

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Author’s note: Scotty declares that the finest views he has personally enjoyed of the Double Cluster was with a 6 inch refractor equipped with a special 4 inch focal length ocular designed by Art Leonard. This author has observed these clusters with all manner of instruments, including opera glasses, a three draw spyglass with a one inch diameter objective, binoculars of various sizes, as well as a plethora of astronomical telescopes. Arguably the best view was enjoyed with a rather specialised 8″ f/6 doublet achromat (utterly useless at high power though), but these days he is completely sated with the medium power views served up by his workhorse instrument, a 8″ f/6 Newtonian reflector.

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The final pages of this opening chapter discusses a number of NGC objects in the far southern constellation of Fornax. On page 23, Houston discusses the visibility of the planetary nebula, NGC 1360:

A short notice on this object was in Deep Sky Wonders for 1972, and it surprises me now. I wrote that NGC 1360 was not seen in a 4 inch reffractor but glimpsed with a fast 5 inch refractor; a sad testimony to the murk of my Connecticut skies that evening…

pp 23.

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Author’s note: This is an intriguing statement, and one that flies somewhat in the face of much contemporary ‘wisdom’. Afterall, a quality 4 inch long focus refractor (his beloved Clark) ought to see things ‘better’ than a fast achromat only an inch larger, right? Wrong! Scotty had little reason to prevaricate. The larger instrument showed up this magnitude 9.4 Robin’s Egg Nebula, where the 4 inch apparently could not; and under the same conditions!

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Chapter 2: February

The chapter begins in the rather lacklustre constellation of Camelopardalis, to an oft overlooked galaxy that presents as quite a spectacular sight from a dark sky site; the barred spiral galaxy NGC 2403. Scotty comments that it was,

too bad Messier missed this spiral while hunting comets. If it had been included in his list, it would certainly one of the better known galaxies in the northern sky. Sky catlogue 2000.0 lists NGC 2403 as about 1/4 of a degree and shining with a total light of an 8.4 magnitude star  values similar to famous Whirlpool Galaxy, M51. Indeed, NGC 2403 is the brightest galaxy north of the celestial equator that does not have a Messier number. pp 28

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Author’s note: One can find NGC 2403 about 7.5 degrees northwest of the third magnitude star Omicron Ursae Majoris (Muscida). My observations indicate that it is somewhat larger than Scotty’s quoted size; more like 25 x 13 arc minutes and thus covering an area roughly half that of the full Moon.

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NGC 2403 featuring supernova 2004DJ as imaged by Rochus Hess using a 25cm f/5 Newtonian astrograph.

As Houston rightly points out, this remarkable non Messier object is well seen in large binoculars and is a ” lovely gem” in his 4 inch Clark refractor. He also points out that the famous American comet hunter, Leslie C. Peltier, included NGC 2403 in his list of galaxies used for testing out the suitability of a telescope for comet hunting. Through his 10 inch reflector the view was transformed into “an ocean of turbulence and detail.” This is more like the description this author recognises in his 8 inch f/6 Newtonian at powers of 100x or so.

Scotty then goes on to describe another galaxy in the celestial Giraffe; IC 342, first discovered by the great English amateur astronomer, W.F. Denning in the 1890s. Houston quotes this galaxy as a 12th magnitude spiral galaxy and is very much more faint than NGC 2403. Scotty was unsure about whether it constituted a bona fide member of the Local Group. Today, we know for sure that it is. This author has not seen this faint galaxy personally, but it shouldn’t present as too much of a difficulty in an 8 or 10 inch telescope with averted vision and low powers.

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Author’s note: The integrated magnitude of IC342 is quoted as between 8.4 and 9.1 depending on the source; both of which are considerably brighter than the magnitude 12 figure quoted by Scotty on page 29.

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Intriguingly, Scotty mentions that despite several attempts to see IC 342 with a number of 4 inch refractors, he never managed to see it with such instruments, but does go on to say that, “using a 10 inch reflector I noted it as easy and even stands 100x once located.

I wonder what you see?

Kemble’s Cascade. Image Credit: Wayne Young.

On page 30, Scotty presents his wonderful word painting of one of the most striking asterisms in the entire heavens; Kemble’s Cascade:

Despite more than half a century of peering into nooks and crannies and looking where the guide books were silent, I missed one of the sky’s more beautiful asterisms. In 1980 a letter from Lucian J. Kembe, who lives under the clean skies of Alberta, Canada, told of a fine grouping he had come across.While sweeping  with 7 x 35 binoculars in Camelopardalis, kemble found a “beautiful cascade of faint stars  tumbling  from the northwest  down to the open cluster NGC 1502.” I called the asterism Kemble’s Cascade when writing about it in this column. The name has stuck.

pp 30

It was Houston who honoured Fr. Kemble with this discovery; a remarkable feat in itself as was apparently unnoticed by earlier observers. Kemble’s Casacade runs for about 2.5 degrees all the way from Cassiopiea right down to the open cluster NGC 1502 in the Camelopardalis. My 80mm f/5 achromatic refractor frames the entire line of some 15 stars (the brightest of which is magnitude 5) using a 32 mm Plossl delivering 13x. The magnitude 5.7 cluster, NGC 1502 is also worth scrutinising with binoculars or a small telescope, where some four dozen members can be made out with a concentated gaze.

Gaius; the author’s 80mm f/5 refractor.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scotty also points out that the cluster is home to two interesting multiple star systems for small telescopes; Struve 484 and 485. The former is a pretty communion of three suns, with the two fainter members separated from the primary by 5.5″ and 22.5″. The latter is a wonderful amalgam of nine suns, seven of which have magnitudes in the range  7 to 13th magnitude and according to Scotty are, “within reach of a good 4 inch telescope” pp 31. The remaining two members, he says, are within range of a 8 inch telescope.

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Author’s note: I can confirm that a good 8 inch reflector can tease all of the Struve 485 members fully apart and is quite a sight for sore eyes, as one might imagine.

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During the early 1980s, new filter technologies were coming to the fore that would soon render objects previously considered all but invisible plainly seen. This would come about with the invention of broadband and narrow band filters and it is noteworthy that Scotty lived during this era;

At the 1982 Texas Star Party, I was asked what was the best new challenging deep sky object after the large aperture Dobsonian revolution had dispatched most of the test objects from the 1950s and ’60s. I suggested the california Nebula, not knowing that a piece of modern technology would soon remove it from the the list of challenges; a skyglow piercing nebula filter. In fact, I remember saying that it is the ultimate test object for visual observers. So much for that wisdom, for little did I realize when I made the comment that before I returned to Connecticut I would see the nebula with my naked eye through an O III filter. In the winter of 1992, in Mexico, the same filter showed the California nebula as bright.

pp 34.

Scotty informs us that this extraordinarily elusive object (prosaically referred to as NGC 1499) in Perseus was discovered visually by the young E.E.Barnard in 1885 using the 6 inch Clark refractor at Vanderbilt University, Nashville, Tennessee. Barnard is well known for possessing incredibly acute vision, especially for faint objects on the precipice of vision. On page 35, Scotty offers his regal advice to observers wishing to see this object;

A low magnification should be used so that the field of view shows plenty of sky to contrast with the object. the telescope’s optics should be well collimated and free from dust and dirt that would scatter light and reduce the image contrast. The eyepiece also should be clean , and all air to glass surfaces antireflection coated. While a number of things affect the visibility of Low Surface Brightness (LSB) objects. I suspect that seeing them depends more on observer experience and eye training than on specific telescope f/ratios and magnifications.

pp 35

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Author’s note: From a dark sky, away from the artificial lights of towns and cities, cast your gaze immediately north of xi Persei. NGC 1499 spans a whopping four full Moon diameters (two angular degrees) in extent. If you can’t spot it with the naked eye, try holding up a Hydrogen beta filter (which transmits at 486.1nm), which should greatly help in the visual discernment of this emission nebula. A regular Deep Sky filter should also help. The hydrogen gas that constitutes the bulk of the nebula is excited by  xi Persei, which is itself a member of the Perseus OB2 association of hot, young stars. Telescopically, one ought to choose a small rich field telescope offering as wide a field as possible, and again, one should couple this to an appropriate filter. Good luck in your endeavours to see this amazing structure!

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Page 35 recounts a number of ways amateurs have seen the California Nebula over the years. Perhaps the most endearing is that described by a one Alister Ling from Montreal, Canada, who wrote Scotty with this tale. He was visiting his friend, David H. Levy, and took a small boat out upon a lake near his cottage where the air was exceptionally tranquil (think Big Bear Solar Observatory):

I made a monocular from my 400mm telephoto lens by attaching a 28mm orthoscopic eyepiece to it. This gives a magnification of about 14x and a field several degrees in diameter. No sooner had I located xi Persei than the extended nebula was quite obvious. It was about 1.5 degrees long with two fairly bright stars embedded near its edge. Roughly near its midpoint there is an obvious kink in the nebulosity. It appears more like a mass of unresloved stars than a gas cloud; very much as the Milky way appears to the naked eye. Later, a crescent Moon rose in Gemini, and rendered the California Nebula invisible.”

pp 35

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Author’s note: Those were the days eh! Fun with a makeshift telescope! I can’t imagine many folk doing something like that now. Note also how the nebulosity completely vanishes in moonlight!

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In the clear, cold nights of winter, the dazzling constellation Perseus stretches its silvery fishhook high in the northern sky. The Milky Way narrows considerably in Perseus, being partly veiled by interstellar dust, and we are looking well away from the center of the galaxy, in Sagittarius. Star charts show that the open star clusters which abound in Cassiopeia and Auriga are noticeably fewer in Perseus. But the constellation does offer many objects that will reward the observer who braves the cold weather to observe them.

pp 36

With words such as these, how could anyone resist the opportunity to venture outside on a clear winter’s night to observe the glory of the firmament? Scotty understood that the stars offered a kind of comfort that could not be found elsewhere. He was drawn to them, like a duck to water.

We move from Perseus briefly to explore a splendid telescopic object; M27 (NGC 6853), the Little Dumbbell, in the diminutive constellation of Vulpecula, the Fox, at the head of Cygnus. One of the brightest of the planetary nebulae, it is easily seen in binoculars as a 8th magnitude misty glow. Scotty says it’s hard to find though, and he’s right! Thankfully, he offers the reader an easy way to locate it;

Start with Phi Persei. This star and a dimmer one just to the south from a pointer, with Phi at the head that directs the observer to a diamond of faint stars, within which M76 is dimly perceptible.

pp 36.

The Little Dumbbell (M76) in Vulpecula. Image credit: Robert J. Vanderbai.

A telescope transforms the binocular view immeasurably. In my old 4 inch f/15 achromat, it appeared as a roughly boxed shaped object, greenish in hue, and about twice as long as it is wide. It responds well to high magnification. 200x is the order of the day. Two lobes of this planetary nebula are seen projecting out at either end with a pretty smattering of faint stars strewn across its face. Scotty decribes it thus:

With a small aperture or in indifferent sky conditions, M76 shows only a dim irregular oval with ragged edges. But one night, with an 8 inch reflector in the hills of the Golden Gate in san Francisco, M76 was a most exciting object.It appeared more than 2′ by 1′( large for a planetary) and high magnifications brought out an intricate network of tubulent celestial clouds.At Stellafane in Springfield, Vermont, M76 appeared as a marvelous object in George Scotten’s 12 inch f/5.7 Dobsonian reflector. The nebula seemed to float between us and the starry background, its edges appearing  even more faryed than when smaller telescopes are used. Its curled twists and streamers seemed to show the whole mass in turmoil. At the 1992 Winter Star Party in the Florida Keys I had a chnace to view M76 through a 36 inch Dobsonian reflector built by Tom and Jeannie Clark. To reach the eyepiece required climbing a stepladder half as high as the surrounding palm trees, but the view was worth it. it made anything I had ever seen in my old 10 inch reflector just a dusty memory.

pp 37.

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Author’s note: Scotty vividly describes what amateur astronomers refer to as ‘aperture fever.’ That said, though he most certainly enjoyed and appreciated the views through giant light buckets, there is no evidence that he ever personally succumbed to them. Evidently, he was completely sated by much smaller, simpler kit.

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From Vulpecula, we venture back into Perseus once more, where Scotty discusses the bright open cluster M 34. Situated about half way between Algol (the Demon star) and the famous double star, Gamma Andromedae (Almach), this magnitude 5.2 open cluster is an excellent target for binoculars or a small telescope.Scotty was of the opinion that the best views of this cluster were to be had with 15 x 65 binoculars, although I think the view is equally compelling at 13x in my 80mm f/5 refractor. A 4 inch telescope shows up a few dozen stars loosely associated with each other and varying in brightness from the 8th to the 12th magnitude.

Many observers, including Scotty, have noted additional structures inside the cluster more reminscent of that seen in globulars than any other type of object. Scotty also mentions the interesting double star at its heart.

I see three noteworthy curved rays of stars running out from the center which are very  evident in my 4 inch Clark refractor at 40x. Indeed, they even show in binoculars. Near the center of the swarm  lies the double star Otto Struve 44, which my 4 inch refractor splits nicely at 100x, especially when the heater is turned on to remove any trace of dew  from the objective. The primary star is of magnitude 8.5 and 9.2 companion is 1.4″ distant at position 55 degrees(toward the northeast)

pp 39

One of the great charms of reading the work of historical figures is the thrill of discovering new information about how our hobby has changed over the years and, just as importantly, how it has not changed! Such knowledge is valuable. On page 40, Houston says that until the 1970s, most deep sky charts never listed objects fainter than about 13th magnitude. The reason he says is because truly big telescope mirrors were hard to come by because they rapidly became too heavy and unwieldy. Back then, mirrors were made with a diameter to mirror thickness ratio of 6:1. A 6 inch mirror was already one inch thick and a 12 inch would have to be 2 inches thick!  And those big mirrors didn’t come cheap either:

Such mirrors larger than 12 inches cost a fortune.

pp 40

And yet, Scotty was an accomplished ATMer:

In 1932 I made a 10 inch reflector from 1/2 inch plate glass. The mirror had to be carefully supported or else it made every star in the field appear double; pretty but hardly suitable for astronomy.

pp 40

Indeed, Scotty goes on to say that during the early 1930s, the largest telescope dedicated to serious amateur observing was a 13 inch reflector donated by Cornell University to the Milwaukee Astronomical Society.

By the 1980s, advances in manufacturing technology ensured that virtually any good sized star party across the United States had good telescope mirrors 20 inches or larger in size, allowing the 13th magnitude barrier to be broken. As a test for this 13th magnitude + limit, Scotty offers the galaxy trio, NGC 1130 (magnitude 13.0) and NGC 1129(+14.5) and finally NGC 1131 (+15.5). According to Scotty, these should all be visible in a good, modern 10 inch reflector from a suitably dark site.

The remainder of the chapter discusses the huge and winding constellation of Eridanus, the celestial River. Alas, owing to my own far northerly location (56 degrees) only the northernmost tip of this constellation (to the southwest of Orion), is on view and thus I’m not in a position to comment on many of the objects Scotty discusses here, which are better suited to those observing at more southerly latitudes.

As darkness settles on the February landscape, the mighty Hunter Orion stands high over the southern horizon. Now is a fine time, however, for observers living in northern temperate latitudes to explore the backwaters and eddies of the the River Eridanus cascading westward from brilliant, blue white Rigel. Eridanus meanders in graceful loops and bends before disappearing below the southern horizon, where it ends at Achernar deep in the southern sky at declination –57 degrees.

pp 42.

The majestic barred spiral galaxy, NGC 1300 in Eridanus. Image credit: Hubb;e Site Images

Scotty goes on to inform us that Eridanus offers no star clusters to the observer but does have a profusion of galaxies. One good target for small telescopes is NGC 1300, a rather fetching barred spiral galaxy, with a visual magnitude of 10.3. Houston says:

It is within reach of a 4 inch, and I have seen it easily with a 3.5 inch Questar telescope.Though photographs  of NGC 1300 with larger telescopes reveal a central bar with two thin but tightly wound spiral arms, smaller amateur instruments show only a blurred spindle. A 4 inch f/12 oof axis reflector suggested some detail in the glow but fell short of showing any spiral structure. A 10 inch or larger will give a more diatinct image, about 6′ x 3,’ and may even reveal the faint companion to the north, NGC 1297.

pp 43.

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Author’s note: This is arguably one of the most accessible galaxies in Eridanus even for those living at high northern latitudes. You can find it by panning about 2.3 degrees north of third magnitude Tau Eridani. An 8 inch or larger reflector and power of about 200x gives quite a good view of its main features.

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In discussing NGC 1232, found just 3 degrees southwest of NGC 1300, Scotty mentions something curious;

In my 4 inch refractor it seems to be better seen with a 150x eyepiece than with a 50x used in combination with a 3x Barlow lens. This is curious, for usually a Barlow and a long focus eyepiece give a view a view superior to an eyepiece of shorter focus that is used alone.

pp 44.

What do you think?

On page 45, Scotty commences a fascinating discussion on the ‘natural tools’ deep sky observers employ in order to see faint objects on the edge of visibility. In particular, he mentions averted vision, long known to experienced observers, but stresses that it is not equally effective for all observers. Some folk get more out of it than others, as it were.

And, like any other human endeavour, visual astronomy is not an exact science. There are exceptions to every rule:

In experiments at the Naval Research Laboratory in the late 1950s, one subject actually saw less as the image approached the edge of his retina. However, one exceptional individual’s sensitivity increased steadily in both colors; the gain in red light was three magnitudes in a direction 40 degrees from the fovea. These experiments, by J.L. Boardman, were done with scotopic(dark adapted) vision……. Until the tyro observer acquires the skills needed to ferret out fainter deep sky targets, there is often a period of frustration at the eyepiece.

pp 45.

The moral of the story here is that no book or instruction manual can ever reveal the optimum method of visualing faint fuzzies. Personal experimentation is the only sure way of getting ahead.

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Chapter 3: March

Walter Scott Houston was the complete observer. He was as happy looking with his naked eye, as he was with the help of various optical accoutrements, particularly binoculars and telescopes. Curiosity drove him.

It is in this vein that Scotty opens his topics for discussion for the month of March, and in partcular, to a beautiful, though quite elusive object in the wilds of Monoceros.

On a trip to a high altitude site in Northern Mexico he recalls:

The first target was an old favorite of mine, the Rosette Nebula( NGC 2237–39) to the east of Orion in the stellar wilderness we call Monoceros. Without a filter only a tiny glimmer of light was visible, but with an ultrahigh constrast (UHC) filter the nebula burst forth in specatcular fashion. I know of no other object in the sky where flicking back and forth in front of a naked eye produces such a wonderful effect.

pp 49

It is true indeed true that the Rosette Nebula, or that “elusive wreath of winter”, as Scotty referred to it, is often better seen in a finder ‘scope than the main instrument. Binoculars allow one to easily centre the open cluster embdeed at the epicentre of this highly complex structure; NGC 2244 easily found about two fifths of the way between ruddy Betelgeuse and brilliant white Procyon. My 80mm f/5 achromatic telescope shows up about two dozen stellar members at 50x, but larger telescopes show even more stars in the hinterland. Finding the surrounding nebulosity, of course, is an entirely different matter. Its fairly low altitude in my winter sky renders it exceptionally challenging and I’ve only glimpsed the brightest (western) edge at low power in the same telescope in the wee small hours of the morning (when the glow from Glasgow, 25 miles to the south is minimised, or ‘Glasglow’ as I disaffectionately refer to it), after a cold front has swept the air clean of particulates. Inserting a nebular filter (and powers below 50x or so) to dim the stars of NGC 2244, immeasurably improves the visibilty of the brightest parts of the associated nebulosity.

Imagers have revealed the Rosette to be enormous in relative terms; fully 1.3 square angular degrees in extent. And what a photographic spellbinder it is too!

The beautiful Rosette Nebula in Monoceros, as imaged by Andreas Fink using an 8 inch f/4 GSO imaging Newtonian.

 

 

 

 

 

 

 

 

From page 49 through 52, Scotty launches into a wonderful discussion about the Rosette Nebula, detailing how this object was discovered piecemeal. Sir William Herschel, for example, discovered the open cluster NGC 2244 but entirely missed the nebula. Neither was it seen my Charles Messier or Admiral W. H. Smyth. William Lassell however, observing with his splendid 48 inch speculum reflector from the pristine, dark skies of Malta in the 1860s, described the same cluster with the nebulosity!  And while seeing parts of the emission nebula once took on the mantle of a test object, the arrival of modern nebular filters have long removed that distinguished status from it.

From Monoceros, we move northward into the constellation of Gemini, the Heavenly Twins, where Scotty waxes lyrical about arguably one the finest Messier Objects in the northern sky; the enormous, tumbling chaos that is M35:

M35 is my favorite open cluster. Located about 2.5 degrees northwest eastward of Eta Geminorum, it is an an impressive frame of bright stars with a softly flaming background of fainter ones, seemingly containing hundreds of members. William Herschel did not include the cluster in his general catalog of deep sky objects. It was his way of honoring Messier as the man who, through his earlier catalog of about a hundred deep sky objects, had inspired him to conduct his own sky survey.

pp 52

I agree wholeheartedly with Scotty in considering M 35 to be the most visually stunning open cluster in the starry heaven. It has the uncanny ability to induce gasps of delight each time I run my telescope through this region, situated at the northern foot of the constellation.

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Author’s note: Eta Geminorum (Propus) mentioned in passing by Houston is also a most challenging binary star, consisting of a marmalde orange giant star (possibly variable owing to its advanced age, and first noted as such by Julius Schmidt back in 1865) with a much fainter bluish companion that is seen to ‘bleed’ from the primary under high magnifications. Very tough for a 4 inch telescope, this author has enjoyed his finest display of the rather elusive secondary using a 8 inch f/6 Newtonian on the frosty evening of December 12 2015. See here for details.

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M 35 (lower right) as imaged by the 2MASS all sky survey.  Note also the fainter cluster NGC 2158 just off centre right. Image credit: Wiki Commons.

M35 is so large that its glory is often lost in rather small, restricted fields of view offered up by large telescopes. Yet, every increment beyond binoculars causes M35 to increase in majesty. My 80mm achromatic telescope shows it well, but the view is greatly improved in my 5.1 inch f/5 reflector at 20x. But it is with my largest telescope, an 8 inch f/6 reflector, equipped with a 40mm wide angle eyepiece delivering 30x, that I drank up my finest views of the system in recent years. Scotty seems to have enjoyed a somewhat similar viewing experience to my own;

To me, M35 seems most lovely in a 6 inch at 40x; though I must admit that, through a 36 inch telescope and a wide field eyepiece, this blaze of interwoven stars is an awe inspiring sight. But I have probably viewed M35 the most with my homemade 10 inch reflector. This was my workhorse telescope years ago on Louisiana and Kansas. Wide field eyepieces were rare during the 1940s and ’50s so, using a pair of achromats and fooling with the spacing between them, I made a wide field eyepiece with passable quality. It was a copy of what 19th century photographers called a landscape lens, and it wasn’t far removed from the design now commonly called a Plossl. ….With this eyepiece on the 10 inch I could get all of M35 into a single field. The view was too beautiful to describe with mere words. Bright stars were scattered with cosmic recklessness across the field, and it was difficult to establish where the cluster’s edges dissolved into the stellar background.

pp 54.

After enjoying the sheer magnificence of M35 through the telescope you’d be forgiven to have totally overlooked the fainter open cluster located a mere 0.4 degrees to the southwest of it. But once you ‘discover’ this other system, NGC 2158, it’s like the icing on the cake. Doubtless, were it located in some other, less extraordinary patch of sky,  this rich but faint open cluster would be more often cited by deep sky observers. It is thus easy to see why, historically, it was all but overlooked by early telescopists. NGC 2158 is poorly rendered in my 80mm f/5 refractor but is quite prominently displayed in my 5.1 and 8 inch reflectors at low and moderate powers.Here’s Scotty’s description of the cluster;

The dim, arrow shaped cluster lies right on the outer edge of M35 and is a pitfall awaiting careless observers. In my youth NGC 2158 escaped my attention until one exceptional night. From the 1920s on I had looked at M35 many times, mostly with 4 and 6 inch telescopes, but occasionally with the Milwaukee Astronomical Society’s 13 inch reflector. Then while observing with a 10 inch f/8.6 reflector in 1952 under the excellent skies of Manhattan, Kansas, I accidently discovered a peculiar wedge shaped object. For a few heartbeats I thought I had discovered a comet! Fortunately, before announcing my “comet” to the world, I checked the Skalnate Pleso Atlas Catalogue and found that it was the small star cluster NGC 2158.

pp 55.

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Author’s note: Scotty’s ‘discovery’ of the ‘comet’ near M35 is par for the course for any experienced deep sky observer. And while NGC 2158 seems for all the world like it is physically associated with M35, it actually lies some 10,000 light years farther away than its more illustrious neighbour!

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Pages 57 through 62 are devoted to two rather special ‘deep sky’ objects, multiple stars to be more precise; Castor( Alpha Geminorum) and Sirius (Alpha Canis Majoris). Scotty recounts his own personal history with both systems, how their brighter companions have changed their orbital distances and position relative to their primaries over the decades and centuries, as well as some of the historical personae associated with them. Castor presented Scotty with one of his earliest visual feats; resolving it into two components in the 1920s using a “1 inch homemade refractor.”

Sirius B, first seen by accident by Alvan G. Clark in January 1862, whilst testing a new 18.5 achromatic doublet objective for Dearborn Observatory, Illinois, was actually deduced to exist some 18 years before it was observed by the German astronomer, Friedrich W. Bessel (not mentioned in the text by Scotty). The system also caught Scotty’s attention as a young man, where he managed to split the pair with a truly famous instrument:

I first split the pair in 1932 with the same 6 inch Clark refractor used earlier by the famous double star observer Sherburne W. Burnham.

pp 61.

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Author’s note: Wow! What an honour that must have been! S.W. Burnham was a gifted (and entirely self taught) double star obsever. He saw things that still stretch credulity!

The brighter companions to Castor (B &C) and Sirius B can currently be enjoyed in very modest backyard ‘scopes. A 3 inch refractor and moderate powers ought to easily bag both.

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And it was Burnham’s equally famous colleague and friend, E.E. Barnard, who, Scotty reliably informs us, discovered a whopping five new nebulae within one angular degree of brilliant Castor in 1888!

NGC 2410 lies 1 degree north of the star, whilst the others ( IC 2194, IC 2193, IC 2199 and IC 2196) lie even closer in, off to the southwest of Castor. All are in the 14th and 15th magnitude range.pp 61.

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Author’s note: I have never searched for, yet alone seen any of these objects, but they’d make an interesting project for a dark, moonless, winter’s evening in a moderately large telescope.

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Appropriately enough, Scotty dedicates the next couple of pages of the book to another Messier showpiece, M41, located just 4 degrees south of the Dog Star. As always, delightful words stream from Scotty’s thought flow:

In contrast to Sirius, the field below is dark and vacant, allowing the eye to regain some of its sensitivity. After a minute or two this mighty galactic cluster rides into view. Its stars shine with  the total light of single 4.5 magnitude sun, which puts the cluster well within range of the naked eye. It would probably be better known as a naked eye target were it not so low in the sky as seen from northern temperate latitudes.

pp 63

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Author’s note: From my far northerly latitude M41 is always very low when it transits the meridian, making it a considerably more difficult object to see visually (though it certainly can be seen!). A good binocular object, my 5.1 inch reflector at 60x shows the system well, revealing about three dozen stars spread over an area slightly larger than the full Moon, though I suspect that were it higher in the sky I might be able to divine still more members.

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Messier 41 in Canis Major as imaged by NASA’s 2MASS survey. Image credit: Wikicommons.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scotty also mentions two faint open clusters discovered by Clyde W. Tombaugh (about whom this author will have much more to say in an up and coming chapter) located about four degrees east of M41 (pp 63 to 64).

Did you know that the month of March offers up more 1st magnitude stars than any other from northern latitudes? Trust Scotty to notice and with great literary poise:

During March evenings eight 1st magnitude stars sit in solemn conclave in the sky above my Connecticut home. Two are in Orion, while the others are arranged in orderly grandeur around the great Hunter. Three naked eye star clusters; the Pleiades, Hyades and Praesepe; are strung along the ecliptic carrying with them a wealth of ancient folklore. Near the meridian beams the Great Orion Nebula, also visible to the naked eye. Galactic clusters are legion in the winter Milky Way, and overhead Capella shepherds a profusion of them in Auriga.

pp 65.

You can tell where Scotty is going to venture next; that splendid trio of open star clusters in the celestial Charioteer: M36, M37 and M38, as well as a few other systems of lesser splendour.

The stellar storm that is M37. Image credit: NOAO.

Scotty says M37 is the prettiest of these, and I would agree. It’s easy to find a little southeast of the midpoint between Theta Aurigae (itself a good double star for small telescopes) and Beta Tauri. First described by Hodierna back in 1654, it was independently discovered by Messier over a century later. My 80mm f/5 glass shows up a respectable 50 or so members at 50x. There’s also very pretty 9th magnitude orange star marking its epicentre, which only adds to the great natural beauty of the system.

Here’s how Scotty describes M38:

Moving “down” the Milky Way, we run into such variegated sar fields and clusters that it almost impossible to know where to halt, but this might very well be at M38. Although this cluster is well within the star strewn, it is usually visible to the naked eye without much effort.It is certainly far easier than M33(the Triangulum Galaxy), and probably easier than M11, the Scutum cluster. Evenly compressed into a glowing ball two thirds the diameter of the full Moon are over a 100 softly blazing suns. M38 is a magnificent in any sized instrument.

pp 66

Houston then calls our attention to paths less travelled, beginning with the magnitude 7.5 open cluster, NGC 1893, located just 3 degrees west of M 38. My 8 inch reflector at 100x unveils about four dozen stars arranged in a wedge shape some 12′ in size. The cluster is enveloped in a cocoon of gas and dust, IC 410, a sure indicator of its very young age (of the order of a few million years). This creates the somewhat hazy appearance of the cluster as seen in small telescopes, but Scotty raises some interesting questions all the same:

In small apertures the cluster does show a haze of unresolved stars, but, as mentioned, NGC 1893 is involved with the nebula IC 410. Like many observers, I have looked at the cluster but not seen the nebula. Could the glow we attribute to stars just below our telescope’s limit really be due to the nebula? Has anyone examined this group with a nebula filter? The results might be startling.

pp 66

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Author’s note: You can indeed see traces of the IC 140 nebulosity by employing an OIII filter coupled to a moderately large aperture ‘scope. My 8 inch reflector shows up the most prominent whisps toward its northwestern edge, but a 12 inch will transform the view into something quite spectacular. NGC 1893 is an active region of star formation.

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Scotty discusses other, less well celebrated open clusters in Auriga on pages 67 through 68 for those who enjoy a faint fuzzy challenge. In the remaining pages of this chapter, he covers a few objects of note in the southerly constellations of Columba and Lepus.

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Chapter 4: April

This chapter opens with a discussion of the novel constellation of Lynx, introduced by Hevelius in the 17th century to fill the space between the cluster rich constellation of Auriga ad the galaxy rich Ursa Major. Scotty’s first target is NGC 2419, found by panning your telescope about 7 degrees north of Castor. Shining at magnitude 10.3, this globular cluster is of particular interest owing to its great distance from the solar system; 330,000 light years, by the best estaimtes. That places it about twice as far from us as either of the Magellanic Clouds.  Yet, all the while, though its remoteness is truly mind boggling, NGC 2419 is well seen in a small telescope;

Despite its great distance, NGC 2419 shines at about 10th magnitude and appears a little less than 2′ across. Under good observing conditions the cluster should be visible with a 3 inch telescope. I once saw it from Kansas with a 4 inch refractor stopped to 2 inches and 100x. The cluster should always be within reach of a 6 inch glass, and a 12 inch may start to show some hint of individual stars around the edge. It is a beautiful object for a 17 inch. More distant globular clusters have been discovered on photographs made with the 48 inch Schmidt telescope on Palomar Mountain. However it is unlikely that any would be within the visual reach of amateur astronomers.

pp 77

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Author’s note: Scotty, like virtually all of his contemporaries, thought that NGC 2419 was a true intergalactic ‘interloper’ unhinged from the gravitational influence of the Milky Way but the latest research suggests it is indeed bound up with our galaxy taking approximately 3 billion years to complete one orbit.

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Scotty concedes that while Lynx is home to about a dozen galaxies, most are very faint. The exception he says is NGC 2683, which is an unexpectedly bright spiral galaxy (magnitude 9.8). Scotty accurately describes it as “cigar shaped” about 3 times as long as it is wide. While discussing this, he brings up some interesting points about the merits of having a stable mount and the relative efficacy of ‘sweeping’ as opposed to studying a ‘steady’ view:

In general, a loss of 1.5 or 2 magnitudes occurs when a rigid stand is not used.I was amazed at how much better my 20 poer Apogee telescope performed after a solid support was made for it.  Experienced observers know that bright objects can be seen during a sweep, while those near the telescope’s magnitude limit require the field of view to be steady. It helps to know exactly where to look. In this way I was able to locate NGC 2683 with a 3 inch aperture at 60x……..yet it is an easy object in a 4 inch telescope on just about any night.

pp 77.

NGC 2683, a magnificent spiral galaxy in Lynx and easily in reach of small backyard ‘scopes. Image credit: Wiki Commons.

Author’s note:  NGC 2683 can be a spectacular object in a large telescope. Arguably the best view I have personally enjoyed was with a 12 inch Dob at 150x, where I was able to see clear signs of mottling. The northwestern edge of the galaxy is also seen to extend further from the core than its southwestern counterpart.

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Scotty briefly discusses several other moderately bright galaxies in Lynx, including magnitude 10.9 NGC 2859 just west of Alpha Lyncis, followed by NGC 2500, NGC 2782 and  NGC 2844 (see pages 78 and 79). From here, Scotty turns his attention to one of the finest galactic sights visible in the northern sky, the ‘dynamic duo,’ M81 and M82, which are exceptionally well placed high in the sky on April evenings.

Both M81 and M82 are easily found about 2 degrees east southeast of the 4th magnitude star, 24 Ursae Majoris. Visible in a 50mm finder from a dark sky site, the view improves with every increment in aperture. Morphologically though, they could hardly be more different.;

While M81 is a textbook example of a spiral galaxy, its companion, M82, is anything but. It is in fact, one of the most unusual galaxies within the range of small telescopes.At magnitude 8.4, it is also within the grasp of binoculars.

pp 81

M81 ( bottom) and M82 (top) ; a sketch made by the author using his 80mm f/5 achromatic refractor on the evening of March 14 2015.

 

Scotty draws our attention to a number of less celebrated galaxies within easy reach of this pretty galaxy pair. Indeed, they are all part of the so called M81 galaxy group, including the magnitude 10.2  NGC 2976, which is well seen in my 8 inch reflector at 150x. You can find it just 1.4 degrees south southwest of M81. Scotty says he got a good view of this galaxy with a 2.4 inch (60mm) classic Unitron refractor.pp 81.

On pages 82 to 83, Scotty embarks on another discussion about some interesting double stars, in particular, Beta Delphini, which he says, “never gets more than 0.7″ apart.” What comes next is fascinating:

Typical is the report of Charles Cyrus of Baltimore, Maryland, whose 12.5 inch f/7.2 reflector has no clock drive. At 572x he saw the components clearly separated.

pp 82

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Author’s note: Scotty is a breath of fresh air! Here is yet another account of a reflecting telescope splitting sub arc second pairs! And Mr.Cyrus evidently didn’t even use a clock drive! This is in perfect agreement with my work with two reflectors; a 130mm f/5 and a 204mm f/6; both of which have been shown to be excellent double star instruments.

The interested reader will also find some tips on page 83 on how best to tease apart the closer pairs with various telescope types.

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On pages 84 through 87, Scotty discusses one of the finest and accessible open clusters in the northern heavens; the famous Beehive Cluster (M44) and its interesting hinterland. Spanning a region of sky fully 1.5 degrees wide, M44 is a mesmerizing sight in a small, richfield telescope at low power. You can find it by pointing your telecope to a spot midway between Castor & Pollux in Gemini and Regulus in Leo.

My 130mm f/5 reflector presents the entire star cluster beautifully at 20x and, unlike many other deep sky objects, it closely resembles the nickname bestowed upon it.

The celebrated Beehive Cluster (Praesepe) in cancer. Image credit: Miguel Garcia.

Here’s how Scotty describes the Beehive:

In low power fields, finders and binoculars, M44 is a brilliant show object. It has no sharp boundary. No one can say for sure where the cluster’s faint glow merges into the placcid sjy background. And the center is hardly brighter than the edge.The cluster appears as a ghostly sheen of cobwebs at least a degree in diameter, sometimes maybe two. Through a large telescope, the view is not particularly impressive, because the stars are widely scattered. But the cluster is an exciting object for binoculars and rich field telescopes. the best instrument for viewing M44 is one that has a field of at least 1.5 degrees across with the largest aperture that will still give an exit pupil no more than 7mm in diameter. I had an excellent view of an object with my 4 inch Clark refractor and a special eyepiece of 4 inch focal length designed by Arthur Leonard.

pp 86 to 87

For the remainder of the chapter Scotty calls our attention to various deep sky objects in Hydra, which snakes its way below the ecliptic, from Cancer in the west to Libra in the east.

In the introduction to this section, we gain valuable information concerning the origin of the Messier Marathon:

The idea of a Messier marathon; an all night session to view as many of the Messier objects as possible; sprung up independently in several locations. According to Harvard Pennington, president of California’s Pomona Valley Amateur Astronomers (PVAA), the first marathon dates to the late 1960s and a group of observers in Spain. On this side of the Atlantic, it was the mid 1970s before amateurs in Florida and Pennsylvania took up the challenge. Unaware of the earlier efforts, California comet hunter Don Macholz suggested a Messier marathon in an article published in the San Jose Amateur Astronomer’s newsletter in 1978.Pennington claims that the cat got out of the bag when I wrote about the Florida and Pennsylvania projects in my March 1979 column. After that, marathons became inceasingly popular.

pp 89.

Perhaps the most celebrated Messier object in Hydra is M48, found by moving your telescopic eye about 3 degrees south southeast of 4th magnitude Zeta Monocerotis. Binoculars reveal a few dozen members with a somehat triangular shape, and with a steady hand and my 130mm f/5 Newtonian and low power shows up at least 70 members arranged loosely over a field just shy of one angular degree. What ever item of equipment you have, M48 is well worth a gander under a dark sky.

Scotty offers some interesting background information concerning this beautiful open cluster:

The open cluster M48 was long believed to be a “missing” object until Harvard astronomer Owen Gingerich linked it with NGC 2548, which Caroline Herschel discovered in 1783. If Gingerich is correct, the original published position for M48 was about 5 degrees in error. Seemingly Messier made a mistake of 5 degrees in declination, but his right ascension is correct. But this identification seems pretty certain since there is no other nearby candidate matching Messier’s visual description of M48.

pp 90

Over the next few pages Scotty deals with a number of fainter objects in Hydra, as well as the far southerly spiral galaxy, M83.

The wonderful Planetary nebula in Hydra, NGC 3242. Image Credit Wiki Commons.

As previously mentioned, Houston underwent cataract surgery on his right eye in the summer of 1980. Many of his fans became concerned that he might give up observing all together, but their fears were soon allayed when he declared that it actually gave him a new lease of life! In particular, because a cataract selectively absorbs shorter wavelengths of visual light over longer ones, it can induce a colour bias to the objects one sees through the telecope. Scotty disclosed how his new, artificial lens perceived the bright planetary nebula, NGC 3242:

Ron Morales found NGC 3242 easily with a 6 inch f/5 telescope at 50x. Recently I looked at it with my 5 inch Apogee telescope and a 20x eyepiece. It appeared slightly oval but without the pointed ends so prominent in photographs of the object. The central star was easily seen with my eye that had its lens removed during cataract surgery. The star appeared almost as bright as the entire planetary in this eye, while it was hardly visible at all in my normal eye. This was surely due to a greater amount of ultraviolet (UV) light reaching the retina of the eye without its natural lens. Central stars in planetaries are generally strong emitters of UV.

pp 95.

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Author’s note: Scotty reminds us all that growing old need not inevitably lead to reduced observing activity. His artificial lens allowed him to see objects in new ways, enhancing rather than hindering his enjoyment of all things astronomical. I wonder whether he also saw that little bit more chromatic aberration through his beloved Clark achromat?

Younger individuals usually report a bluish tinge to planetary nebulae, becoming more green as one matures in age, but there are always exceptions.

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Chapter 5: May

The magnificent Omega Centauri. Image credit: ESO.

When the jet stream bulges soutward, it allows Canadian air to pour across the United States and cover all but the far West with a stable mass of cold dry air.Amateur astronomers benefit with dark nights of crystalline transparency and better astronomical seeing. Under these conditions it is no problem viewing 5th magnitude stars only 1 degree above the horizon. Globular cluster fans should wait for that special evening to try for Omega Centauri, the finest of all globulars. The search must be done when the cluster is at its highest point in the sky. On May evenings the cluster lies near the meridian. It culminates at the same time as Spica; just look for the cluster 36 degrees below the star.

pp 99.

Shortly before his death in 1993, Twinky ventured south to the Florida Keys to make his maiden observation of Omega Centauri, the finest globular cluster in all the heavens. In many ways, seeing this outstanding natural beauty was the icing on the cake for this humble man who truly loved the heavens.

Unfortunately, owing to its extreme southerly latitude, it never rises anywhere near the horizon from my far northern latitude. But it is one object that I long to see. Those lucky enough to have seen it inform me that with a telescope of 8 inches aperture about 1,000 stars can be made out at high power. And with larger telescopes, red supergiant stars can be distinguished within its seething mass.Of course, one doesn’t have to travel below the equator to see this wonder of the heavens, as Scotty explains:

In theory, an observer in the Northern Hemisphere can see into southern declinations as far as the corresponding colatitude(down to 90 minus the latitude of your location). From geometry alone we can calculate that Omega Centauri should be visible from as far north as 42.5 degrees north latitude. In practice that value is too small, because atmospheric refraction at the horizon lifts starlight by 0.5 degrees, so Omega might be viewed from 43 degrees. The challenge is to see it through terribly dense and contaminated air. Ordinarily horizon mists, smoke, and dust take a good 10 or 15 degrees off this figure.

pp 101.

What follows is a fascinating discourse on what a number of amateurs have experienced while observing Omega with various telescopes.

Progressing further through the May chapter, Scotty returns to more familiar territories, partcularly the subject of galaxy visibility. On page 103 through 105, he describes an interesting experiment carried out by a few enthusiastic amateurs concerning the factors that affect the visibility of faint galaxies in Leo Minor, specifically NGC 3414, NGC 3504 and NGC 3486, all of which hover around the 11th to 12th magnitude. The results, unsurprisingly, were far from clear cut, involving aperture, magnification and interpersonal variation.

Scotty learned from experience that two eyes are better than one:

Lately I have become increasingly aware that more can be seen with two eyes than with only one (Microscopists have known this for centuries).

pp 103

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Author’s note:

The author’s fine old binocular compound microscope by Vickers (formerly Thomas Cooke & Sons, York, England)

Although I certainly appreciate the value of two eyes when using a microscope, I have still to explore fully the advantages of binoviewing in astronomy. Unfortunately, though my (limited) experiences of using them have been exercises in frustration more than anything else, I don’t doubt that they would enhance my observing experience. Binoviewers are on my future ‘to buy’ list.

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On page 105 through 106, Scotty, now entering the 1990s, reminisces about how the world of astronomy has changed from the time he was young.

As we begin the last decade of the 20th century, I’m flooded with the realization of how much astronomy has changed in my own lifetime and how rapidly it continues to change. In the 1930s I remember when the first photoelectric measurements of starlight were made using an electronic amplifier. Back then we only dreamed of space rockets. But today those rockets loft telescopes into space with detectors thousands of times more sophisticated than that crude photometer of the 1930s……Amateurs work very differently now than they did only a few decades ago. For example, in the early years of deep sky observing  I would set up a small refractor near my home in Milwaukee’s Bay View. With a copy of Norton’s Star Atlas in hand (the only deep sky reference commonly available  at that time), I would sweep the sky. Today’s beginners are likely to have an 8 inch or larger telescope and access to detailed charts showing hordes of galaxies.

pp 105/6

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Author’s note: Times have certainly changed, and for the better. Indeed, amateur astronomers have never had it so good! High quality items are now available at very reasonable prices, allowing most anyone with a modest income to enjoy the night sky. Other things have deteriorated though; light pollution, for example. Many amateurs(perhaps the vast majority) live in cities, where the glory of the night sky is a mere shadow of its true self. Amateurs are forced to travel further and further to seek out truly dark sanctuaries.

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The next target on Scotty’s list is Leo I; a 10th magnitude dwarf galaxy in the constellation of the Lion. It’s very easy to locate, yet quite a challenge to see details in! Locate 1st magnitude Regulus in a medium to high power eyepiece and cast your gaze just 20 arc minutes north of it. If your sky is good and dark, you’ll spot a ghostly glow roughly 10′ in size. Now move Regulus just outside the field in order to increase the contrast with the background sky. Quite a challenge, undoubtedly, but worth chasing up in a moderately sized backyard ‘scope.

On pages 108 through 114, Houston discusses that happy hunting ground for galaxy observers spread across the face of Leo. Scotty provides a sense of the scale of this richness for the reader:

While the deep sky objects in Leo might seem a little drab compared with the brilliant star clusters scattered across the Winter Milky Way, there are some remarkable sights here for 8 inch and larger telescopes. Burnham’s Celestial Handbook lists over 70 deep sky objects in Leo. All are galaxies from the 9th to the 13th magnitude. I wouldn’t even try to guess the number a 17 inch telescope could find. Within the boundaries of the constellation there is not one open or globular cluster or planetary nebula suitable for amateur telescopes. This is interesting because Leo is the 12th largest constellation, covering just under 947 square degrees of sky.

pp 108

The amateur equipped with a modest telescope will thoroughly enjoy these pages on the galaxies of Leo and Leo Minor, as Scotty’s expertise walks you through them. You can enjoy many of these deep sky objects with a small telescope, as he exemplifies. Indeed, some of these galaxies don’t look all that better even when a very large telescope is employed to study them. For example, concerning NGC 3245, Scotty has this to say:

The galaxy is not difficult in my 4 inch Clark refractor at 100x. I once viewed it with a 20 inch Clark refractor at Wesleyan University, and, while it appeared larger and brighter than in the smaller telescope, I did not notice much additional detail.

pp 116.

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Author’s note: Fishing out faint galaxies takes patience. A good dark sky is a huge bonus. Once you see one, the eye has the uncanny ability to pick out several others in rapid succession.

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The last few pages of this chapter are dedicated to one of the sky’s brightest galaxies; NGC 3115 in Sextans. More famously known as the Spindle Galaxy, this bright lenticular galaxy can be tracked down a little over 3 degrees east of 5th magnitude star, Gamma Sextantis. Scotty prefers to let the sky do the work;

Select an eyepiece which shows at least a Moon’s diameter of sky, and place the 5th magnitude Gamma Sextantis near the southern edge of the field. If you leave the telescope stationary for 12 and a quarter minutes(turn the drive off if the telescope has one), the galaxy will be centered near the northern half of the eyepiece field.

pp 120

Houston seems well smitten with this galaxy, referring to it as a “splendid” sight in his small telescopes(pp 120). Indeed, he reckons it looked pretty much the same in his 5 inch Apogee telescope as it did in a 12 inch instrument!

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Author’s note: In my 5.1 inch reflector at 100x, NGC 3115 is clearly tear shaped, about four times as long as it’s wide. My 8 inch Dob shows just a little more detail, with a highly condensed core and a slightly fainter outer ‘halo’. All in all, a marvellous Island Universe to track down and observe on a dark and moonless Spring evening.

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Chapter 6: June

One of the nicest pieces of celestial real estate for hunting down cosmic treasures is the area around the Bowl of the Big Dipper. Aside perhaps from Orion, the Big Dipper is the sky’s best known objects. And what a wonderful selection of objects there is, for it is here in the polar region that the great stream of galaxies reaching northward from Virgo and Coma comes to a brilliant conclusion. Severla bright galaxies from the Messier catalog bedeck the Dipper amind scores of others that are easy targets for 6 inch telescopes.

pp 123/4

With these beautiful words, Walter Scott Houston opens his June chapter, turning his attention to the famous asterism of the Big Dipper, which is better known in Europe as the Plough. And rightly so, for this ‘flower basket,’ as Scotty refers to it, dominates the sky near the zenith during June evenings and thus is very well placed for exploration with binoculars or a backyard telescope.

The first object he addresses is M97 (a.k.a the Owl Nebula), one of the faintest in Messier’s famous catalogue. From my northerly vantage, June is arguably the worst month to see this object, as our skies are filled with seasonal twilight at this time. Nonetheless, you can find this planetary nebula just less than 2.5 degrees southeast of Beta Ursae Majoris(Merak). Scotty says it can be picked off in 15 x 65 binoculars and is easily visible in a 4 inch telecope. The Owl responds well to increases in telesope aperture. My 8 inch reflector coupled to an OIII filter at 120x reveals a colourless, rotund object some one tenth the diameter of the full Moon. A little scrutiny will show the nebula’s two ‘eyes’ staring back at you. Seeing the central white dwarf star is another matter though. While some astronomers claim it can be seen in apertures upwards of 16 inch, I have never laid eyes on it with a telescope of this size.

The Owl Nebula ( M 97). Image credit: Wiki Commons.

Scotty mentions how Admiral W. H. Smyth, observing in the 19th century with a 5.9 inch Tulley refractor, referred to this object as a “pale uniform disc about the size of Jupiter” (pp 124).

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Author’s note: Surely this is a gross underestimate of its true size! More like three Jove diamters. Smyth was right on the money about its hue however, as something this faint will not yield colour to the eye in all but the largest telescopes. Photographically, that’s a different matter however, as the image above illustrates.

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“It’s only a short hop,” Scotty says, “of 0.8 degrees northwest from M97 to the spiral galaxy M108, which can be seen in the same low power field.”

Yes indeed! Both objects are perceptibe in the same field of view of my 80mm f/5 refractor charged with an ocular delivering a one degree field. My 8 inch f/6 reflector at 150x shows 10th magnitude M108 to be a delicate sliver of light about four times as long as it’s wide. It also picks up the 12th magnitude star bleeding forth from near the centre of this edge on spiral galaxy.  This star, which is actually located well in the foreground of the galaxy, has doubtless fooled many an observer over the years into thinking it’s a supernova.

From here, Scotty describes how to find M109 and M106, together with interesting historical titbits, well worth reading(see page 125).

Scotty then focuses his attention on the sky inside the Bowl of the Big Dipper;

The Dipper’s Bowl also contains a fair number of 11th magnitude galaxies and fainter galaxies which generally go unmentioned in amateur observing guides.

pp 125

While Scotty mentions several NGC objects I have not personally observed, the one exception is NGC 4605, which is easy to see as a fuzzy oval in my 80mm refractor at 50x. Shining with an integrated magnitude of +10.9, it presents as rather mottled at 150x in my 8 inch reflector. Here’s how Houston describes it:

This 10th magnitude spiral lies nearly on the extension of a line joing Gamma and Delta Ursae Majoris. It is obvious in 65mm binoculars , and a large telescope makes it a fine sight, extending across a 5′ x 1.2′ area of sky.

pp 126.

On pages 127 through 129, Twinky discusses the curious mystery of M102, and specifically how it was misidentified as a duplicate obsservation of M101. Or, if you were to believe Admiral W.H. Smyth, it is to be identified with NGC 5866. Irrespective of what version of history you agree with, NGC 5866 is easily seen in my 5.1 inch f/5 reflector at 85x as a beautiful sliver of light with a highly condensed centre. You can find it manually by moving your ‘scope about 4 degrees south of the magnitide 3 luminary, Iota Draconis. My 8 inch reflector at 200x shows a very prominent dust lane coursing through its midplane.

NGC 5866 is alovely sight in a modest backyard ‘scope at high power. Image credit: Wiki Commons.

The memory of winter begins to ebb in June as mild but crisp nights complement the celestial riches now in the sky. Arcturus shines overhead, and Corona Borealis, the Northern Crown, is at its dainty best. Draco coils its pinpoint stars about the ecliptic pole, and the great globular cluster M13 is climbing up the eastern sky. It doesn’t matter if you use binoculars or a 20 inch telescope, there is so much to see that you wish for an impossible succession of crystal clear nights; but where to begin?

pp 129

Scotty clearly thought of everyone when he wrote his monthly deep sky observing columns. There’s enough for each and everyone to enjoy, using whatever equipment one chooses. Where Scotty lived, Arcturus passes overhead. But at 56 degrees north, it can never reach such heights.

Scotty next calls our attention to a curious triangular patch of sky, the vertices of which are marked by three stars; Eta Ursae Majoris, Alpha Canum Venaticorum and Gamma Bootis. Wiithin such a triangle, more or less, three prominent Messier galaxies can be found; M51, M63 and M94.

He begins appropriately enough with the Whirlpool Galaxy (M51), easily located by panning your telescope a shade less than 2 degrees southwest of Eta Ursae Majoris. Scotty presents this wonderful face on spiral galaxy in curious terms;

The Whirlpool offers challenges for any telescope. For example, what is the smallest aperture required to reveal the spiral structure? Lord Rosse first detected spiral structure when he turned his giant 72 inch reflector on the galaxy in the spring of 1845. Today, with our vision sharpened by knowledge, the spiral features of of M51 are visible in instruments as small as 10 inches , and some observers have glimpsed them in a 6 inch telescope in very dark skies. An 8 inch is sufficient for me, but John Mallas needed a 12.5 inch in a dark desert sky. He correctly noted that experience and exceptional transparency are important for success. In 1936, I had a very good view of the spiral structure using the University of Arizona’s 36 inch reflector in Tucson.

pp131

The wonderful Whirlpool Galaxy (M51) in Canes Venatici. Image credit: Wiki Commons.

Author’s note: I fully concur with Houston’s comments on this fascinating object. By far the finest view I have personally experienced of the spiral structure of M51 was through a good 16 inch reflector at an altitude of over 8,000 feet in the White Mountains of northeastern California. It was an amazing sight in those dark and crystal clear skies; it embodied a somewhat translucent appearance, more like living protoplasm than anything else. Such a memory is very hard to erase from the mind’s eye!

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On page 132 Scotty discusses M63, famous for its weird and wonderful spiral arms, found by moving the telescope about two thirds of the way from Eta Ursae Majoris to Alpha Canum Venaticorum. The latter system is better known as Cor Caroli, a splendid double star for the large binoculars or a small telescope. My 80mm f/5 refractor at 50x thows up a beautiful scene consisting of a blue white primary, magnitude 2.9, separated by about 19″ of dark sky from its yellowish secondary (magnitude 5.5). Nature is full of beautiful things that are easy to see and find!

On pages 134 through 135, Houston presents an excellent overview of what he calls, “the Wonder of M106.” To locate it, I find it easiest to start at Chi Ursae Majoris and then move 5.5 degrees or so eastward into Canes Venatici. This is a big (20′ x 9′) and bright galaxy (magnitude 8.3). My 8 inch reflector throws up a wonderful view of this grand spiral at powers of 150x or so, and even shows distinct signs of mottling (owing to prominent dust lanes, I suppose) in its spiral arms with a concentrated gaze.

The magnificent spiral galaxy M106 as imaged by the Hubble Space Telescope. Image credit; Wiki Commons.

Concerning M106, Scotty declares:

Ronald Morales viewed M106 with his 10 inch Newtonian reflector. Using a power of 87x, he described it as “extremely large; very bright with a bright, compact center; extended in a north to south direction with a large, fuzzy outer envelope.” Years ago in Kansas  I viewed the galaxy with a 10 inch reflector at about the same magnification and saw a “very bright parallelogram shape with fragile spiral arms at the end of the major axis.” The nucleus appeared uniform with little variation in brightness,. Other observers using 8 inch telescopes have reported M106’s appearance as long and needle like, and one saw a dark area near the nucleus. So much for consistency!

pp 135.

Scotty wanders into the constellation of Coma Berenices for the next section of this chapter. Bereft of stars brighter than about the 4th magnitude, the eye is naturally drawn to its northeastern corner where one can make out a very extensive haze of celestial light covering about 4.5 degrees of sky. This is Melotte 111, or the Coma Berenices Star Cluster. Scotty says opera glasses, providing a magnification of just 2x or 3x (pp 136) work wonders with this bona fide cluster of stars, where about three dozen luminaries can be made out, ranging in glory from the 5th to about the 10th magnitude.

From here, he continues to discuss the three globular clusters present in Coma. M63, he says, is unimpressive in a 3 inch telescope, but magnificent in a 12.5 inch. Then there’s 11th magnitude NGC 5053 about which he says, “in large instruments it is a little gem of woven fairy fire.”

What a wonderful turn of phrase!

Moving into Virgo, Scotty preserves a curious project that dates to the time of Sir William Herschel:

There is a strip of sky here near declination +02 degrees where several galaxies and a beautiful globular cluster can be readily located by means of a technique that dates back to William Herschel. The procedure is simple; set your telescope on a prearranged starting point, leave it stationary, and watch celestial objects drift through the field according to a timetable. For this purpose, select a low power eyepiece with a field not much less than 1 degree across. To check the field size of an eyepiece, time the drift of an equatorial star centrally across it, and count one minute of arc for every four seconds of time.Once that’s completed select a star lying west of the desired galaxy, but having the same declination. The telescope is then left stationary, allowing diurnal motion to carry the object into the center of the field.

pp 138

Scotty goes on to show how this age old technique, involving little or no modern technology, can enable you to see the edge on spiral galaxy NGC 5746 and a globular cluster in the same field! See pages 138 through 140 for more activities of this ilk.

There is never a shortage of deep sky objects. Whatever the season, the sky holds more than enough of these delights to keep you busy all night, every night; if you take the time to search them out with good charts and reference books……

pp 140

Scotty clearly believed that an amateur astronomer was responsible for his/her own entertainment, however unusual or off the beaten track it might seem to others. Enthusiasm (and not necessarily elaborate equipment) is the key to unlocking such treasures; activities that can keep a star gazer happy for a lifetime.

The interacting galaxies in Corvus known as the Antennae. Image credit: ESA.

The final pages of the June chapter discusses a number of objects in Corvus,  a constellation this author is not familiar with owing to its low position below the ecliptic upon culminating the southern horizon as well as the full blaze of twilight experienced during the summer months. Nonetheless, on pages 140 through 145, Scotty discusses a number of interesting objects within the sky enclosed by the stars of the celestial Corbie. Arguably the most interesting is the famous Ringtail Galaxy, or the  Antennae. Here’s how Scotty describes it:

Several times amateurs have sent descriptions of what they believe is this galaxy, but I’m sure they believe they have mistaken another galaxy for the Ringtail. My 5 inch 20x Apogee refractor shows the pair as a bright blob. An observation made with my 4 inch Clark refractor under the indifferent skies of my old home in Haddam,Connecticut, revealed NGC 4038/39 to be alittle more than an assymetrical 11th magnitude blur. However, at a campsite near Big Sur, California, I viewed a wealth of detail in the Ringtail with a borrowed 12 inch reflector. Other reports in my files support this…

pp 145.

At the end of this chapter, Scotty returns northwards into Virgo, where he discusses the Sombrero Galaxy (M104), a far lovelier sight in April than in June at my location. My 5.1 inch reflector at 100x can just begin to show me the dust lane in this edge on spiral galaxy, though Scotty claims that the experienced deep sky observer, John Mallas, couldn’t detect it in a good 4 inch refractor (pp 146). It’s obvious in my 8 inch reflector though at similar powers. And while you’d be mistaken for thinking that it’s a bona fide part of the Virgo cluster of galaxies, M104 is actually located some 25 million light years closer to the solar system.

The inspiring Sombrero Galaxy ( M104) in Virgo. Image credit: Wiki Commons.

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Author’s note: Scotty’s claim of Mallas being unable to clearly see the dust lane in a fine 4 inch f/15 refractor (that’s what he used!) resonates quite well with the author’s experience on another target; the faint double star, Pi Aquilae. In other work, it was shown that this pair of stars (magnitude 6.3 and 6.8), separated by 1.5,” was a challenging target for a 4 inch f/15 refractor (illustrated earlier)  but was considerably easier with a 130mm f/5 Newtonian. The reason was simple; the 4 inch runs out of light earlier than the 130mm, so at the magnifications employed (approximately 270x) it’s just easier to see these stars as separate in the larger aperture Newtonian. The same is probably true of the Sombrero.

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Chapter 7: July

By now, the shortest nights have passed away and Scotty gets his teeth stuck into the wealth of wonderful objects on view during the longer nights of July. Personally, this is one of my favourite chapters from the book,  as it covers such a wealth of familiar objects I like to visit as a casual (read non serious) deep sky observer.

The opening pages (131 through 134) of this chapter are dedicated to a seasonal favourite and, historically speaking, a very important celestial treasure in the sheme of things; the famous planetary nebula in Draco, NGC 6543, more affectionately known as the Cat’s Eye Nebula. This 9th magnitude object is fairly easy to track down about 5 degrees east northeast of the third magnitude sun, Zeta Draconis.To my eye, this is one deep sky object that actually resembles the name bestowed upon it; a blue green feline eyeball staring back at you from the depths of space. In my 5.1 inch reflector at 100x, it is quite large; about 18″ in diameter. The central star is clearly visible; quite a feat when you think about it, as it is a hot and highly luminous white dwarf star much smaller than the Sun, and shining with an equivalent brightness of an 11th magnitude star. I find the view at 200x in my 8 inch reflector to be nothing short of stunning!

The famous Cat’s Eye Nebula in Draco as imaged by the Hubble Space Telescope. Image credit: Wiki Commons.

Scotty describes what NGC 6543 looks like in all sorts of equipment, including the homemade 1″ refractor he first spied it through as a boy. It also includes a description of the view experienced by a one Michael  Gardner through the 60 inch reflector atop Mount Wilson in California(152/3). Scotty also informs us that the English amateur astronomer, Sir William Huggins, examined this planetary nebula with a crude spectroscope attached to an 8 inch refractor back in 1865, finding it to be quite distinct from any stellar body he had previously examined!

In the next few pages Scotty turns his attention to two varibale stars in the constellation of the Northern Crown; Corona Borealis (T CB and R CB).

At his location, at mid northern latitudes, July is an excellent month to track down some of the finer globular clusters in the summer sky and Houston wastes no time discussing these fascinating objects in detail, including M13 and M92 in Hercules, the ‘rival of M13’ in Serpens, M5 as well as a string of globular favourites down in Ophiuchus (pages 157 through 165). The reader is warmly encouraged to sift through this excellent literature and put some of Scotty’s suggestions to the test.

It’s always nice when Scotty includes a double star of note in his monthly columns (the ‘deep sky’ objects I am most acquainted with). In this capacity, he mentions the charming little binary system, 70 Ophiuchi on page 166;

In 1989, the 4.3 and 6.0 magnitude components were near a minimum separation of 1.5″

pp 166

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Author’s note: 70 Ophiuchi is a beautiful colour contrast double star system, consisting of a yellow primary and orange secondary, orbiting their common centre of gravity in 88 years. A perennial favourite, the pair is currently widening towards their maximum separation, which will occur around 2025, after which time they will slowly close in on each other again. Currently, they are easily separated in a 60mm refractor but will require something closer to 80mm as they close in over the years (minimum 1.5″).

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While you’re at it, Scotty recommends scouting out the bright (magnitude 8)  planetary nebula, NGC 6572 (a.k.a The Emerald Nebula), discovered by the famous double star observer, Wilhelm Struve, back in 1825. About the same size as the Cat’s Eye Nebula (18″) discussed previously, it’s a good target for a medium sized backyard ‘scope at high power. You’ll find this object in a low power field about 2 degrees south of the star 71 Ophiuchi.

Warm summer nights are a fine time to relax under a dark sky. As you lie back and scan the ghostly band of the Milky Way and its environs, see how many globular clusters you can detect with the unaided eye. If you observe from mid northern latitudes and can detect 6.5 magnitude stars, there are eight globulars to try for this month in the evening sky; M2 in Aquarius, M3 in Canes Venatici, M4 in Scorpius, M5 in Serpens(Caput), M13 and M92 in Hercules, M15 in Pegasus and M22 in Sagittarius.

pp 168

From a good, dark site, such globulars all seem observable with the naked eye but, as Scotty reminds us, the above assumes they are point sources. And that is not the case, as even through a finder telescope, they present as distinctly non stellar. But what a challenge nonetheless!

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Chapter 8: August

The regions near the north celestial pole are usually neglected by amateurs, who seem more attracted to the spectacular sights farther south. But sometimes we overlook the obvious. Polaris, for example, is a variable star. In fact, it is the brightest Cepheid in the sky.  Sky catalogie 2000.0 gives its range as 0.15 magnitude over a 4 day period, but studies done during the 1980s show that the range is decreasing, leading some astronomers to speculate that the star may cease to vary altogether. Currently Polaris varies by only a few hundredths of a magnitude and is thus well below the range detectable by the eye.

pp 173

With these words, Scotty opens his chapter on the August sky. He takes us to the Pole Star, around which the great vault of heaven rotates, in this epoch at least.  He does mention later (but not here), that Polaris is a multiple star system; with Polaris B being easily accessible to a small backyard telescope. The companion is a lovely sight in my 80mm f/5 achromatic telescope at 50x.

That said, having explored the book’s content thus far, one comes away with the distinct  impression that Scotty wasn’t an overly enthusiatic observer of double stars. Instead he quickly alerts us to a very faint (13.5 magnitude) spiral galaxy, NGC 3172, discovered by Sir John Herschel in the early 19th century, which he christened, “Polarissima”. Needless the say, I’ve not seen it, nor looked for it. Scotty recommends an 8 inch or larger instrument to bag this bounty from the sable depths.

Sticking to far northerly targets, Scotty then moves into Cepheus, and to the open cluster, NGC 7380. You can track this 10th magnitude target down fairly easily, as it lies just a shade under 2.5 degrees east of that most famous of Cepheids; 4th magnitude Delta Cephei. In an area of sky about the size of the full Moon, my 8 inch pulls in about 20 or so stellar members of the 10th magnitude. Inserting a nebula filter will help bring out the brighter parts of the nebulosity associated with it; Sharpless 2:142

NGC 7380 and its associated Nebula imaged using narrow band filters. Image Credit: Hunter Wilson.

In my 8 inch Newtonian at 100x it shows up as a faint, misty fog on a dark night with good transparency.

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Author’s note: Insert a low power eyepiece and revisit Delta Cephei. It has a magnitude 6.3 companion wide away which contrasts beautifully with the rich yellow hue of the primary. It makes a very fetching site in my 80mm telescope at 50x and is also an excellent binocular double.

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The most northern galactic cluster in the sky, NGC 188, is also one of the oldest known, 14 to 16 billion years. It is located just 4 degrees south of Polaris and 1 degree south of 2 Ursae Majoris;

pp 175

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Author’s note: In Scotty’s day, astronomers were not nearly as sure about a lot of things. NGC 188 is now believed to be of the order of 6 billion years old. There was also more unceratinty about the age of the cosmos back then. Today, thanks to refinements in the Hubble Constant (Ho), we are far more sure of its age; 13.799 billion years with an uncertainty of just 0.15 per cent.

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To real meat in this chapter is presented on pages 179 through 184, where he discusses some of the finest planetary nebulae in the northern heavens;

To some people, the ethereal gas bubbles of planetaries have a compelling pull all their own. They float on the foam of the Milky Way like the balloons of our childhood dreams, so delicate they appear. If you want to stop the world and get off, the lovely planetaries sail by to welcome you home.

pp 179.

What a sweet sentiment; to ” stop the world and get off.” Stargazing certainly can do that!

Scotty starts with by far the most famous and well known planetary nebula, easy to find about midway between Beta and Gamma Lyrae; the famous Ring Nebula (M57). Accessible to most any telescope, it’s an enjoyable sight at 100x in my 80mm shorttube refractor, but far more compelling in my 8 inch reflector at the same power.

The magnificent Ring Nebula( M57) in Lyra. captured here by Hubble Space Telescope. Image credit: Wiki Commons.

Appearing a bit more than 1′ across, M57 looks like a 9th magnitude star in finders. The Apogee telescope shows the ring as very bright, but no other detail is visible. At powers of 250x and up, a curious effect takes place. The oval outline of M57 takes on a lemon shape with the ends of the oval appearing rather pointed. They also appear more diffuse and wispy. A power of 600x, however, is none too great if there is sufficient aperture to support it. Even at high magnification, the interior of the nebula retains a thin film of haze that can show some structure.

pp 180/1

Scotty’s comments about this planetary are spot on. M57 looks better and better in larger and larger telescopes. You need large apertures to sustain the very high powers required to discern some of the features he describes. Small ‘scopes just run out of light on this object, limiting the magnifications one can profitably adopt. 200x is a nice place to be with M57 in my 8 inch reflector.

On a top class night, a 12 inch or even a 10 inch telescope can show the planetar’s central star In moments of exceptional atmospheric conditions a 12 inch or larger instrument may reveal a scattering of stars across the central vacancy and even amid the ring itself.

pp 181

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Author’s note: Despite having many, many goes, I have never been able to see the central star in M57 with telescopes of the size described by Scotty. I suspect you’d need a telescope of 20 inches of aperture in this country, and great weather to boot, to have even half a chance to bag this baby!

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On pages 182 through 184, Scotty switches subject to discuss the equally interesting Dumbbell Nebula (M27) in Vulpecula.  Scotty offers a neat way of finding it without setting circles or GoTo:

Set your finder on Gamma Sagittae, the head of the celestial arrow. Sweep about 5 degrees north and you should see an M shaped pattern of stars composed of 12, 13, 14, 16 and 17 Vulpeculae; this group is more conspicuous to the eye than most star charts lead you to believe. M27 is just 0.5 degrees south of the M’s central star.

pp 183.

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Author’s note: M27 is a fascinating telescopic object! It’s huge; fully five times larger than the Ring Nebula but because its light is spread over much greater area it has much lower surface brightness. My 5.1 reflector at 20x easily shows the two bright lobes in an eerie greenish hue. It looks even more compelling in 8 or 10 inch aperture ‘scopes but I find it doesn’t respond well to over magnification;150x to 200x seems about optimal to me. Nebula filters (particularly an OIII)  also work well with larger apertures. Its 12th magnitude central star remains elusive in all but the largest backyard ‘scopes.

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The Dumbbell Nebula ( M27). Image credit: Mohamad Abbas.

Scotty seems somewhat ambivalent concerning the ‘optimum’ sized telescope to view M27 but rightly recognises the importance of aperture;

It is hard to assign a “best” type of telescope for viewing M27. My 5 inch Apogee telescope with a fixed power of 20x shows it as a bright sphere with the dumbbell shape rather mild. My 10 inch f/8.6 reflector shows M27 much better at 300x by means of a Barlow lens less than at the same power with a short focus eyepiece. The latter left the sky gray, and contrast with the nebula was poor.

pp 183

Where Scotty lived out much if his life, the Milky Way in August must have been a wonderful sight, with Scorpius, Scutum and Sagittarius riding a respectable height above the horizon at midnight. Up here on the ‘edge of the Arctic Circle’ only the glory of the northern Milky Way manifests itself. Houston had a habit of asking questions, which at first seemed trvial, but upon reflection, were quite difficult, if well nigh impossible, to answer.  Once such question is this? Where does the Milky Way’s Way edge lie? On pages 186 if discusses this strange question but seems to conclude that, like everything else, it’s dependent upon the kind of ‘filter’ one’s local conditions impose. Whimsically, he calls it ” Houston’s Uncertainty Principle.”

To be continued in Part 2

De Fideli.

Tales from the Golden Age: Hunters of the Red Stars.

The brilliant red giant star, Betelgeuse, shining in the northern winter sky.

 

 

 

 

 

 

 

Do the words of a poem lose their poignancy once its author departs this world?

Can the limp of ‘progress’ outshine the ‘grand procession’ of great accomplishment?

Can a culture, basking in the glory of its own achievement, be made mute by a faithless generation of technocrats?

Can an optical bench test inspire more than a night spent behind the eyepiece of a grand old telescope?

Let us venerate that which is deserving of veneration!

Whose crown shall we adorn with a laurel wreath?

Let us sing again of old dead men

 And clear the cobwebs from their medals.

For they have no equal in the present age

No muse to light their way.

 

 

 

Anno Domini 1866; the Leviathan of Parsonstown, with its six–foot primary mirror, reigns as the largest telescope in the world, bringing international prestige to Irish astronomical science; and both Dublin and Armagh have well established observatories that date back to the end of the 18th century. Their administrators are formally trained, their observing programs, specialised. But far from the Irish cities, west of the great Shannon River, a 50–year–old gentleman, hitherto unknown to the astronomical community, was strolling home along a narrow dirt road that wound its way north from the small town of Tuam, County Galway. It was shortly before midnight on the evening of May 12, that he saw a 2nd magnitude star he had never noticed before in the constellation of the Northern Crown, then situated very high in the sky. After reaching his home at Millbrook House, he sat down by the light of a paraffin lamp to check the star charts in his library. To his amazement, the only star recorded in the position he estimated was of the 9th magnitude, far too faint for even his keen eyes. He had just discovered the brightest nova to grace our skies since 1604; the star T Coronae Borealis!

Such was the meteoric arrival of John Birmingham (1816–1884) upon the world’s stage; an accomplished poet, land owner and man of letters. John was born the son and only child of Edward Birmingham and Elly Bell, who set up home at Millbrook House, near the village of Milltown, from which they received a comfortable income as landlords of a small landholding, itself part of the greater Millbrook Estate. He was educated at St. Jarlath’s College in the nearby town of Tuam and grew up to become a fine figure of a lad, both stronger and taller than many of his peers. Though there is no evidence that he attended university, we may infer from his lifelong interest in scientific matters, particularly geology, as well as his noted ability as a writer, he received an excellent and well balanced education, acquiring significant scientific knowledge from the greater popularisers of his day. Records do show however, that he was actively involved in famine relief during the years 1846 and 1847, which claimed the lives of a million people; about one eighth of the population; from starvation or the associated epidemic disease that swept the nation between 1846 and 1851. Another two million souls emigrated in a period of a little more than a decade (1845-55).

Birmingham spent about six years travelling through Europe in the late 1840s through to the mid 1850s, learning the language and culture of the nations he visited, and spending the majority of his time in Berlin, where he eked out a living from the circulation of interesting scientific articles for popular journals and newspapers, often writing under a pen name. It was here also that historians suggest he had his first encounter with the astronomical world. In particular, he took a great interest in the work of the famous German astronomer, Johann Franz Encke (1791–1865), with whom he established a strong bond of friendship. Birmingham returned to his ancestral home in the late 1850s, ostensibly acquainted with the language and literature of the French and German tongues.  The skies in this part of Ireland were often overcast and dominated by weather systems rolling in from the nearby Atlantic, but on clear evenings, the sky would have been gloriously clear and wonderfully transparent, purged of dust and other particulates; skies that would have commanded a visceral sense of awe and wonder in the young Irishman.

Johann Franz Encke (1791–1865), German astronomer. Image credit: Wiki Commons.

By all accounts, his earliest astronomical equipment was very modest; most likely a small spyglass delivering a fixed magnification of 23x, but it is clear from his later discovery that he cultivated an excellent knowledge of the naked eye heavens. The apparition of Donati’s Comet in 1858 and the Great Comet of 1861 induced great excitement in Birmingham, penning a string of prize winning essays on their appearance and significance;works which appeared in some of the most prominent British and Irish newspapers of the time. But his political connections raised eyebrows among some members of the Imperial establishment. The silver tongued Birmingham was a patriot and associated with British politicians sympathetic to the cause of Irish independence.

Perhaps the latter fact helps to illuminate the bizarre way in which the discovery of the eruptive variable star was made known to the outside world. In the wee small hours of May 13, Birmingham drafted a letter to the editor of the London Times and promptly despatched it. It landed in the hands of the editor a few days later, who, after reading it, promptly discarded it in a waste paper basket! When no acknowledgement was received by Birmingham, he decided to bypass the standard modus operandi of contacting the observatories at Dunsink and Greenwich, and instead wrote of his discovery to one of the most accomplished and respected British astronomers of his day; William Huggins (1824–1910), pioneer in astronomical spectroscopy, who ran a very well equipped private observatory from his home at Tulse Hill, London. This time it was well received, and Huggins enthusiastically turned his spectroscope toward it on the evening of May 18, finding it to be quite unlike anything he had ever seen before! A normal stellar spectrum presents as a streak of colours as in a rainbow, with faint dark lines. The spectrum of T Coronae Borealis, on the other hand, presented with very bright emission lines thought to be due to superhot hydrogen gas. Indeed, Huggins believed that the star had ejected a shell of excitable matter.

Sir William Huggins(1824 –1910), a portrait by John Collier, Image credit: Wiki Commons.

Birmingham also wrote to his local newspaper, providing details of his discovery:

I discovered it on the night of the 12th instant, when it appeared the 2nd magnitude, rather more brilliant than Alpha of the above constellation, with a bluish tinge, forming nearly a right angled triangle with Delta and Epsilon. It had nothing whatever of a cometary aspect. The state of the atmosphere prevented my seeing it again until the 17th, when it appeared reduced to the 4th magnitude…….

It was Huggins who endorsed Birmingham’s discovery at a later meeting of the Royal Astronomical Society and, after word of his discovery spread throughout Europe, the German astronomer, Julius Schmidt, based at Athens, was able to confirm, by the consultation of his notebooks, that only hours before Birmingham noticed the brightening of T Coronae Borealis, the star appeared as it normally did. i.e. a faint field object in his 6 inch refractor. Indeed, Schmidt named a lunar crater after the Irishman, located near the Moon’s northern limb, presenting it in his famous map, first published in 1878.

Lunar Crater Birmingham, located by the Moon’s northern limb. Image credit: Wiki Commons.

The discovery of T Coronae Borealis dramatically changed the course of Birmingham’s life and from there on in, he dedicated himself to further astronomical observations. Realising that his existing equipment was not really up to the task of doing any serious telescopic work, he set about acquiring a suitably powerful instrument. Huggins had enthusiastically assisted Birmingham in his telescopic researches, warmly recommending that he acquire a moderate–sized Cooke refractor for the purposes of continuing his work. Indeed, we know that Birmingham had visited some acquaintances at Scarborough, a seaside town not far from where Thomas Cooke & Sons of York had set up their world renowned telescope making workshops. The instrument he finally acquired in 1869 was a fine 4.5 inch f/15 achromatic doublet, purchased for the princely sum of £120 (still a very large sum by Birmingham’s standards). Curiously, the object glass of the telescope was rumoured to have been made by Howard Grubb of Dublin.

But what, pray tell, would he employ this quality telescope to do exactly? This became over more clear by the opening years of the 1870s, after he struck up a correspondence with one of the great amateur astronomers of his age; the Reverend T. W. Webb, who suggested that he take up the task of hunting down and cataloging the positions and magnitudes of red and orange stars some of which would be variable, a project that was only partially addressed in earlier decades by Sir John Herschel (1792–1871) and the celebrated binary star observer, Friedrich Wilhelm Struve(1793–1864). In addition, the Danish astronomer, Hans Schjellerup (1827–1887), who compiled a list of 280 red stars published in 1866 in Astronomishe Nachricten. His 4.5 inch aperture, long focus achromat would be able to reach stars down to the 12th degree of glory, and with a special, low power eyepiece delivering a power of 53 diameters, he would be able to scan (fairly) large fields of sky. So, the middle–aged amateur from the wilds of the Emerald Isle set about his new avenue of astronomical enquiry; a task he enthusiastically embraced with both hands!

Tiberius; the author’s 5″ f/12 classical refractor; a very similar instrument to that employed by John Birmingham, and used for the purposes of reconstructive history.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Brimingham devoted the next four years of his life searching the sky for red and orange stars. His copious notes show that he would often begin after supper and work all the way through until dawn, weather permitting. Such devotion reflected, at least in part, his bachelor status. He never married and is rumoured to have fathered a child (female).

He was acutely aware of the rather subjective nature of accurately assigning colours to the stars he observed. In particular, his continual correspondence with Webb alerted him to the inherent weakness of the refractor in revealing the true colour of stellar bodies and how the new silver on glass Newtonian refelectors, with their perfect achromaticity in comparison to the former, might be better tools for carrying out such delicate work. We do know however, that Birmingham had the presence of mind to include, where possible, relevant comments from other observers who, at his request, had examined the same stars. He also estimated their brightness in comparison to other field stars. Most of the stars he listed he came across were brighter than magnitude 10 but quite a few were as faint as magnitude 12. During the course of his surveys, Birmingham became intensely interested in the spectroscopic work of Father Angelo Secchi, who had himself collated a list of over 400 coloured stars in 1872 and had begun to subdivide stars into five spectroscopic types. It was during these years that the concept of stellar evolution was first entertained, an idea that greatly appealed to Birmingham and which provided further impetus to continue his surveys.While compiling his list he included Secchi’s available spectral data with his visual notes.

Birmingham’s work cullminated in a list of 658 orange and red stars, published under the title: The red stars: Observations and catalogue, which he presented to the Royal Irish Academy on June 26 1876. The work was enthusiastically accepted and published in August 1877. It is clear from the work that he owed an especial debt to Webb, who had examined about 80 of the stars in his catalogue and provided his own notes on their colour and brightness. Birmingham was also generous to a fault in providing full acknowledgements to all other collaborators.

The red stars also contains very interesting speculations concerning the nature of variables; how and why they brightened and faded. He had himself noted subtle changes in the colour of red variables. In particular, their colour often became paler to his eye as they brightened and deepened in hue as they faded back. This suggested to him that such stars were not dying, as many of his contemporaries held. He also dismissed the idea that the variation in such stars was due to stellar rotation. Birmingham offered his own explanation to explain the variable nature of these red stars, which, in his own words, involved, “the intervention and recession of a nebulous belt around the star.” Taking inspiration from the reddening of the Sun as it approached the horizon (what we refer to today as Rayleigh scattering), Birmingham believed an annulus of dusty material of varied density around such stars could cause them to dim and brighten.

Birmingham was the first observer to note that red variable stars were unevenly distributed in the heavens, being more highly concentrated in a large patch of Northern Milky Way taking in Lyra, Cygnus and Aquila; a swathe of sky he referred to as the “Red Region.”

In the years after the publication of his catalogue, Birmingham became increasingly involved in the spectroscopic designations made by his peers across Europe. For example, he queried Secchi’s assignment of the newly discovered Wolf–Rayet stars to Type IV, and was rather annoyed when the Roman Padre expressed his scepticism that there really existed a concentration of such stars in certain regions of the sky. John’s original work provided fertile ground for other observers to carry out new surveys for red stars. Indeed, Birmingham issued two voluminous addenda featuring a new list compiled by the astronomer, Carl Frederik Fearnley, and another taken from the double star lists of Struve and Herschel.

In the last years of his life, Mr. Birmingham continued to search the skies for more red stars with his 4.5 inch refractor and discovered yet another red star in Cygnus in 1881. He continually updated his list with new spectral data which was streaming in from observers on the continent. In the last year of his life, the Royal Irish Academy, convening at Dawson Street, Dublin, presented Birmingham with its prestigious Cunningham Gold Medal on January 14 1884 for his distinguished astronomical career. Its President, the poet Sir Samuel Ferguson, honoured him with these words:

If I might express an individual opinion I would say that…..you content yourself with noting facts; and shunning plausible but doubtful methods of accounting for them. It is thus [that] solid knowledge is ultimately attained to. Of you let it be said, itur ad astra. Proceed, with the best wishes of the Academy, in your philosophic method, and bear back with you to the Bermingham country this medal, as a token and assurance to our brethern beyond the Shannon that wherever Irishmen devote their leisure to higher learning, there exists for them here, in the capital of their own part of the United Kingdom, a body having perpetual succession, and speaking with the voice of the constituted authority, whose business it is to sympathise with them, to encourage and reward.

This was but one of many accolades delivered to the Tuam astronomer but they were ultimately powerless to change the personal circumstances of his life. The Irish Land League was established with the primary aim to abolish landlordism in Ireland altogether, and to enable tenant farmers to own the land they worked on. As a result, many of the tenants paying rent to Birmingham refused to do so. In addition, he had to fight a succession of legal threats to the title of both his lands and his house. Collectively, these events left him seriously short of income, which resulted in his slump into poverty. Indeed, one of his own tenants described the desperate state of his last days; “he [Mr. Birmingham] was all spent up and starved with the hunger.” He passed away in the early hours of September 7 1884, aged 68 years.

In the aftermath of his death, Birmingham’s house and estate were ransacked and rendered derelict, with much of his written notes and books burned or left to the elements. And what remains of Millbrook House is a but a ruin to this day. Only his wonderful telescope survived, which was preserved for many years at his alma mater, at St.Jarlath’s College, before being handed over to the Milltown Community Museum for posterity.

And yet, all the while, Birmingham’s work was not done in vain, for it was to be taken up once more by a most eccentric Anglican clergyman: Thomas Henry Espinell Compton (T.H.E.C) Espin (1858–1934) who, with singular enthusiam, greatly advanced the story of the red stars.

Espin, the only child of the Reverend Thomas Espin, chancellor of the diocese of Chester, was born in the city of Birmingham on May 28 1858. At age 14, Espin entered the elite boarding school for boys at Haileybury, where his headmaster, himself an astronomy enthusiast, encouraged and instructed his pupils in basic astronomical knowledge. It was the appearance of Coggia’s Comet in the sky in 1874 that really stoked his interest in all things celestial. From 1876 to 1878, he was sent to France to complete his secondary education before going on to Exeter College, Oxford University in 1878 to read for a degree in theology, for which he obtained a good honours degree. Here, his interest in astronomy flourished further when the Savilian Professor at Oxford, Charles Pritchard, allowed him to use the 13 inch De La Rue reflector of 10 foot focus at the university on the condition that he provide practical instruction to other students. It was an offer Espin could not refuse. And he excelled at what he did best; fill people with a sense of wonder and awe for the Universe, as revealed by the telescope. By January 11 1878, aged just 20, he was elected a Fellow of the Royal Astronomical Society(FRAS) during the presidency of Sir William Huggins.

On leaving university, Espin took holy orders, following his father into a clerical career in the Anglican Communion, accepting curate positions first at West Kirkby, Wallasey and Wolsingham in 1881, 1883 and 1885, respectively, before finally taking up permanent residence as Vicar of Tow Law, County Durham, in 1888; a post he was to retain for the rest of his life. In 1880, while at Wallasey Rectory, Birkenhead, Espin wrote to the English Mechanic, proposing the formation of an amateur society aimed at organising and coordinating observations and that the best way to do so was to arrange meetings where local amateurs could discuss their observations in an open and congenial manner. The following year, 1881, the Liverpool Astronomical Society was founded.

After inheriting his father’s estate, he became financially independent, allowing him to pursue many avenues of independent scientific research, much in the same vein as Birmingham before him, including geology, botany and photography. He was an avid student of paleontology, amassing an impressive variety of fossils during his long career; a study that led him to firmly (and rightly I might add) conclude that Darwin’s theory of evolution was bogus. He was also a keen microscopist, with a encyclopedic knowledge of cell biology and the behaviour of Protozoa. Intriguingly, Espin was one of the earliest pioneers in the study of X–rays, and enjoyed using his parishioners as ‘guinea pigs’ in his early experiments!

Espin regarded his vicarage as an ‘open house’ that could be visited any time by his parishioners. They must have been fascinated by his vast collections of books, plants, rocks, fossils and aquaria to cultivate his ‘animalcules’ and pond weed for the microscope. Afterall, he was, like John Birmingham also, a lifelong bachelor. In his garden, he established a small sanatorium in order to provide his sickly ‘flock’ with some relief from the consumption (Tuberculosis). He turned the basement of his home into a gymnasium and even set up a rifle range on his grounds for use by the parish ‘lads.’ All of this was done at the expense of not providing the traditional pastoral care for his parishioners though; he didn’t do house visits. And to top it all off,  he was a well travelled gentlemen and a formidable biblical scholar.

As a boy, Espin explored the heavens using opera glasses and enjoyed a 1 inch aperture Dollond refractor as his first telescope. By the time he entered Oxford University, he was using a 3 inch refractor for his own recreation. Some time later, Espin was presented with a 5 inch refractor by the head of the Harrison line of steamers, a Churchwarden at his old parish of Wallasey, which he used to good effect. While at Wolsingham, Espin set up his first makeshift observatory using the 5 inch refractor and made regular observations through it until he secured his permanent post at Tow Law.

As Webb’s righthand man, Espin assisted his famous ‘elder statesman’ in several revisions of his celebrated Celestial Objects for Common Telescopes. And it was also Webb who piqued Espin’s interest in a fabulous new line of reflecting telescopes being fashioned by master opticians such as George Calver and George With. With these novel instruments he was able to carve out his own unique legacy in the annals of astronomical history. Their generous apertures, much lower cost than traditional refractors, as well as their freedom from chromatic aberration made them a very popular choice for a new generation of amateur and professional astronomers alike. And it was Webb himself who spearheaded this movement across Britain!

We shall not dwell on the historical evidence supporting the above assertion, for this will be covered far more extensively in a separate chapter of the book. That said, in the following excerpt, which is part of a written correspondence between Webb and a one Arthur Raynard, we gain a glimpse of his evangelism for the new silver on glass specula:

It might be worth your while to consider, before finally deciding, the comparative merits of the silvered glass reflector. You have probably heard of this beautiful instrument…. At present it is only in the hands of amateur makers, but their success has been remarkable. One of at least 8 inches clear aperture may be purchased in Hereford for about £26 or £27. As far as looks go, it is certainly very common and clumsy looking affair – being merely a great square tube of stained deal, mounted on a plain wooden stand – and if you regard appearances I could not say much for it. But the Newtonian reflector, under any circumstances, is a singular looking instrument.

Webb had himself proven the worth of these new instruments, acquiring a string of silvered mirrors and complete telescopes. Indeed, according to the noted British double star observer, Robert Argyle, they were able to resolve double stars well below one second of arc:

The 91/3 inch With Berthon reflector was obviously of high quality. One of the regular test objects used by With and Calver was γ2 Andromedae. The 8.5 inch mirrors of both makers were guaranteed to divide the pair, at a time when the separation was 0.6″. Webb also noted, in 1878, that he was able to suspect division in ω Leonis, then at 0.52″, and to divide η Coronae Borealis at 0.55″.

So much for the prognostications of the current generation of amateurs!

It was magic like this that convinced Espin to purchase his first truly ‘serious’ telescope; a 17.25 inch silvered glass reflector by Calver, purchased on Webb’s recommendation in 1885.

Octavius: the author’s 8″ f/6 Newtonian.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Espin most likely purchased the mirrors separately and had the castings for his Calver optics made to order by Lepard & Sons of Great Yarmouth and also by the agricultural firm, Suffolk Iron Foundry, then located near Stowmarket. Espin constructed a modest observatory based on the design of the Reverend Edward Lyon Berthon(1813-1899), another clerical astronomer, which consisted of a small circular equatorial room with a conical roof, and which was commonly known as a ‘Romsey’, after the Parish in which Berthon lived and worked. Espin likely mounted his new instrument on an early equatorial (sometimes called an ‘equestrian’) designed by George With and Edward Berthon (see below).

Shortly before his death in 1885, Webb had alerted Espin to the work of John Birmingham on the red stars. In the months before he died, Birmingham despatched much of his unpublished work to Webb, requesting that he might carry on his observations. Because of his many other duties and failing health, Webb was unfortunately unable to commit to such an undertaking, yet he found a willing and able disciple in the young and enthusiastic Espin.

The With/Berthon equatorial mount( BAA# 83) featuring the 9.33 inch reflector employed by T.W. Webb in his later career. It is likely Espin used a similar mount for his larger 17.25 inch Calver Newtonian. Image courtesy of Denis Buczynski.

 

 

 

 

 

 

 

 

 

 

 

A Curious Aside:

Which is a better tool for red star hunting: a 5 inch refractor or a 8 inch reflector?

A wee experiment: Octavius’ (8″ f/6 Newtonian), and ‘Tiberius’ (5″ f/12 glass) strut their stuff.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Method: A Baader 8 to 24mm zoom eyepiece was chosen to give an approximate exit pupil of about 2mm in both the 5” inch refractor and the 8” reflector, delivering powers of 64 and 100x, respectively. Both instruments were turned on the Double Cluster (Caldwell 14) in Perseus on a dark, moonless evening and the views compared, side by side, for several minutes.

Results: Though the images served up by both telescopes were very fine indeed, the easy winner was the 8” Newtonian. The contrast was a shade better in the unobstructed refractor, as one might expect, but the Newtonian, with its 22 per cent linear obstruction, wasn’t far behind it. These magnificent open clusters contain quite a few ruby stars of varying glory, but the greater light gathering power of the Newtonian (∼1 visual magnitude) made these stars considerably easier to pick out against a dark hinterland compared with the 5 inch glass. The colour of fainter members, in particular, was easier to discern in the Newtonian, a consequence, I suppose, of its greater ability to collect light. Put another way, where there is but a suggestion of colour in the refractor, it is clearly visible in the Newtonian.

From a practical point of view, it was also much easier to study these ruddy stars in the Newtonian, owing to its more comfortable eyepiece position whilst viewing an object high in the sky.

Comments: More light delivered to the retinal cone cells render colour vision more efficacious with the larger aperture. Indeed, no matter how much this author wanted the 5 inch refractor to win, owing to its elegant images, striking good looks, and much greater cost in comparison to the ‘glorified toilet roll’ that is the Dobsonian, it was never to be. Indeed, on all celestial targets examined, under reasonable to good seeing conditions, whether planetary, lunar, double star or deep sky, the Newtonian proved noticeably superior. A comparative MTF graph of a 5 inch refractor and 8 inch reflector will also show this clearly. Many lines of evidence lead to the same conclusion.

The 8 inch Newtonian was the superior instrument for hunting down and viewing red stars. This aperture is probably optimal for all kinds of general purpose viewing, including looking at red stars. Thoughtfully designed Newtonians can do wonderful things!  Here’s an interesting assessment made by a guy from Norfolk (England) of a similar telescope to the author’s modified Newtonian (in terms of raw aperture, coatings, and quality of secondary mirror), only with a slower f ratio and (slightly) smaller central obstruction.

Tiberius; Proxime Accessit.

Octavius; Optimus.

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With his newly acquired 17.25 inch Calver Newtonian installed, Espin, together with his paid assistant, William Milburn, began a new and ambitious search for red stars all across the northern sky. Over the next two years, he found an incredible 3,800 red stars, discovered many new nebulae and over 30 novel variable stars. Such work called for considerable industry and his preserved records indicate that during the dark winter evenings, observing vigils were maintained for over 13 hours! Using an entirely homebuilt spectroscope, he examined over 100,000 stars from Dr. Argelander’s preeminent star charts, with magnitudes as faint as +9.0.

These new data were included in a much more extensive edition of The red stars, which also included contributions from Webb, Copeland, Birmingham and Dreyer, and published, once again by the Royal Irish Academy in 1890. The same telescope was used by Espin and Milburn to discover 2,575 double stars, many of which were measured micrometrically to establish position angles and angular separations. Espin’s proven skill as an inventor was also seen in the many new astronomical devices he made with his own hands, including arguably the first zoom eyepiece offering an assortment of magnifications, a new kind of stellar camera, as well as an improved method of lighting the cross hairs of the micrometer.

To the general public, such routine work as this often went unreported, but Espin received international fame in November 1910 with the discovery of Nova Lacertae, which burst onto the scene with a peak magnitude of 4.6. Over the next 37 days, as the world’s largest telescopes were turned on it, the nova slowly faded back to 7.6 and today it is exceedingly faint at magnitude 14.

For his great contributions to astronomical knowledge, Thomas was awarded the Jackson Gwilt Medal of the Royal Astronomical Society in 1914 for his extensive spectroscopic work, as well as his discovery of Nova Lacertae. It was in the same year that Espin installed an even more powerful telescope at Tow Law; a 24 inch Calver reflector, with which he and his assistant continued to look for and measure new double stars. Curiously, Espin decided to concentrate his efforts on wider pairs, perhaps as a result of noting that the typical atmospheric conditions he enjoyed at Tow Law, Co. Durham, were rarely up to measuring very close pairs. This was the last telescope Espin would aquire and he used it faithfully right up until two years before his death on December 2 1934, aged 76.

                                       The nature and significance of red stars

Red stars, which include the spectral classes M, R, N and S, are not only visually striking to the human eye, standing out against the darkness of the night sky more readily than those with different hues, but they are arguably some of the most fascinating to study! First off, red stars not only include celebrated giant stars such as Betelgeuse, but they also incorporate the smallest bona fide stars in the firmament; the cool dwarf stars that comprise maybe 70 to 80 per cent of all stars that exist throughout the Universe. The largest and most luminous of the red giant stars are some 50 billion times brighter than the coolest red stars (none of which can be seen without a telescope), though they all have effective temperatures ranging from about 3900K (M0) down to 2600K (M8). Their spectra are littered with a maze of strong absorption lines, caused by the presence of simple molecules that absorb light in their tenuous, low gravity atmospheres, including substances such as TiO, CN, ZrO, C3, C2, and CO amongst others. Indeed, these substances collectively absorb so much light (particularly at shorter wavelengths) from their cores, that astronomers have found them difficult to classify in a coherent way. This is because it can often prove exceedingly difficult to trace out their black body curves, in a way that their basic properties can be inferred like hotter stars can.

Red giant stars that have evolved off the main sequence exhibit substantial mass loss in the form of powerful stellar winds and thermal pulses which expel layers of their outer atmospheres to the cold, dark of interstellar space. Cool, dwarf stars, on the other hand, have hardly changed since their birth, and are so parsimonious in their energy generation that they can continue to exist stably for a trillion years or more. And while highly evolved red giant stars are not considered likely candidates for life bearing planets, there has been quite a lot of attention paid to the environments around cool, red dwarf stars, as locations that might harbour viable life bearing worlds.

Doubtless the interested reader may have heard of recent discoveries made by astronomers in regard to a string of planets orbiting close to M dwarf stars. One example widely cited in the media is TRAPPIST-1, located 39.5 light years in the constellation Aquarius. A media frenzy ensued when the team of astronomers monitoring the system announced a cache of seven worlds orbiting the star, all of which  were deduced to have broadly Earth sized masses. The scientists, keen to maximise the impact of their work (thereby securing more funds), stressed the observation that three of these planets lie within the water habitable zone (one of several other ‘habitable zones’ that the scientific community need to talk about, openly and honestly) of TRAPPIST-1 and so could conceivably host some kind of life. But it’s always worth taking a closer look at these planets before jumping to sensationalised conclusions.

Three of these TRAPPIST-1 worlds (designated b, c and d) are of particular interest to astronomers, lying just 1.66, 2.28 and 3.14 million kilometres, respectively, from the dwarf red star’s surface. This means that they will be tidally locked to their star and thus will always show the same face to it as they move in their orbits.This creates potentially enormous differences in the temperatures of the day and night sides of the planets, which doesn’t bode well for life. They are also sufficiently massive and close to each other to exert periodic gravitational influences on one another. These induced perturbations likely rule out the possibility of life on these planets, since it would destabilise and frustrate the travails of any emergent lifeforms on these worlds.

Compounding these difficulties is the physical properties of these dwarf stars. Though only 8 per cent the mass of the Sun, recent XMM Newton observations showed its emission of X rays is comparable to that of the Sun and, owing to their very close proximity to TRAPPIST-1, the resulting X ray irradiance would likely strip away any primordial atmospheres they might have had. Then, to add insult to injury, many of these stars exhibit strong stellar winds, especially in their younger days, when they were engaged in the nurturing of planetary systems. This would require the planets to possess magnetic fields several times stronger than that of the Earth in order to stave off the certain extirpation of any putative lifeforms on their surfaces.

In short, when these physical parameters are factored into the discussion, one can begin to see the unbridled speculation of science journalists shining through. Whether it be the BBC, CNN, or from popular astronomy periodicals, can you not see that they are all hewn from the same stone? They make wild claims that have no basis in a grounded scientific assessment (and the project scientists often make no mention of them which is very telling, in and of itself). Once again, many folk, with their misplaced commitment to methodological naturalism, are only all too willing to give their sovereignty away. What a pitiable state of affairs!

I for one feel most very fortunate indeed to be able to observe the red stars from my back garden, on terra firma!

Update 23.03.17: Still more problems attending the TRAPPIST-1 system, as more detailed 3D climate modelling is done on the planets in this system. Details here.

 

 

Neil English is author of several books on astronomy and is currently writing a largely historical work, Tales from the Golden Age of Astronomy, chronicling the great achievements of historical astronomers over the past four centuries.

 

De Fideli.

 

 

Tales from the Golden Age: The German Selenographers.

Lunar Day by Henry White Warren’s Recreations in Astronomy (1879). Image credit: Wiki Commons.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Do the words of a poem lose their poignancy once its author departs this world?

Can the limp of ‘progress’ outshine the ‘grand procession’ of great accomplishment?

Can a culture, basking in the glory of its own achievement, be made mute by a faithless generation of technocrats?

Can an optical bench test inspire more than a night spent behind the eyepiece of a grand old telescope?

Let us venerate that which is deserving of veneration!

Whose crown shall we adorn with a laurel wreath?

Let us sing again of old dead men.

And clear the cobwebs from their medals.

For they have no equal in the present age;

No muse to light their way.

 

After the publication of Hevelius’ universally celebrated Selenographia in 1647, as well as J.D Cassini’s improvements of 1670, progress with mapping the lunar surface telescopically was painfully slow, entering as it did, a very ‘long night.’ But by the end of the 18th century and throughout much of the 19th century, several German astronomers, amateur and professional alike, using modest telescopes by today’s standards, heralded a golden era of lunar cartography that ushered in the Space Age.

Tune in soon to read the whole story…………………

De Fideli.

A Modern Commentary on W.F. Denning’s, “Telescopic Work for Starlight Evenings (1891).

The monumental work of William F. Denning; "Telescopic Work for Starlight Evenings."

A good quality  modern reprint of William F. Denning’s; “Telescopic Work for Starlight Evenings.”

 

 

 

 

 

 

 

 

 

 

A Work Dedicated to David Gray.

Humility is the fear of the Lord; its wages are riches and honour and life.

Proverbs: 22:4

William Frederick Denning (1848-1931) is not a name that trips off the lips of the modern amateur astronomer. Of all the sky watchers of that era, it is arguably the literary work of The Reverend Thomas William Webb and especially his, Celestial Objects for Common Telescopes, that is most celebrated by amateur astronomers today. But while a great work in its own right, Webb was by no means the only populariser of astronomy in England, nor was he necessarily the most knowledgeable and dedicated to his hobby. That accolade, in this author’s opinion, should be reserved for an obscure Bristolian, who emerged from relative obscurity, in what was the meritocracy of the Victorian astronomical tradition, to pen one of the loveliest treatise on the art of visual observation, both with and without a telescope.

William F. Denning (1848-1931), the doyen of amateur astronomy.

William F. Denning (1848-1931), the doyen of amateur astronomy.

In this essay, we shall explore Denning’s masterful tome: Telescopic Work for Starlight Evenings, first published in 1891, to bring to the modern reader, a distillation of late nineteenth century astronomical knowledge; presented in such a way as to captivate the widest possible audience; both young and old, rich and poor, novice and learned alike. As explained in the preface to the work, the book was conceived at the behest of some of his closest friends, to gather together the best nuggets from his published writings in The Journal of the Liverpool Astronomical Society (of which he served as President in the years 1887-88), The English Mechanic, and The Observatory, among many others.

In Denning’s own words:

The methods explained are approximate, and technical points have been avoided with the view to engage the interest of beginners who may find it the stepping stone to more advanced works and to more precise methods. The object will be realised if observers derive any encouragement from its descriptions or value from its references, and the author sincerely hopes that not a few of his readers will experience the same degree of pleasure in observation as he has done for many years.

No matter how humble the observer, or how paltry the telescope, astronomy is capable of furnishing an endless store of delight to its adherents. Its influences are elevating and any of its features possess the charms of novelty as well as mystery. Whoever contemplates the heavens with the right spirit reaps both pleasure and profit and many amateurs find a welcome relaxation to the cares of business in the companionship of their telescopes on “starlight evenings”.

iv-v

Chapter I:The Telescope, Its Invention and the Development of its Powers

Covering pages 1 through 19.

In this chapter, Denning sets forth his extensive knowledge of the history of the telescope and its development over time. With an engaging writing style, he offers the reader an excellent summary of the key inventions that led to the state of affairs at the end of the 19th century.  Burning glasses, carved into a convex shape, were known to the ancients and were used as magnifying glasses. One such example, Denning informs us, was recovered from the excavations of the ancient Roman town of Pompeii, which met its terrible demise in 79 AD in the aftermath of the eruption of Mount Vesuvius. The Roman writer and philosopher, Pliny the Elder (23-79 AD) also gave mention to globules of glass, which could focus sunlight so intensely that it could ignite combustible material. The development of spectacle lenses from the 13th century onwards is also mentioned, but despite having some grasp of the optical science underlying their prescription, Denning is somewhat perplexed as to why it took so long for their adoption into telescopic devices. That said, he does proffer some tantalising historical titbits that the principle might have been known as early as the fourth decade of the sixteenth century :

Francastor (most probably a one Girolamo Fracastoro) , in a work published at Venice in 1538 states:-

“If we look though two eye lenses, placed the one upon the other, everything will appear larger and nearer.”

pp 4

Denning wryly comments that despite attempts by some fame hungry individuals to claim the invention of the telescope as their own – in particular Galileo Galilei and Simon Marius  – or who pronounced they had ‘figured the principle out’ from basic axiom of physics, it was very likely the case that one of mankind’s most revolutionary devices was very probably elucidated through purely accidental means! Indeed, Denning entertains the notion that the children of the Middleburg spectacle maker, Zachariah Jansen, might have stumbled upon the telescope by placing two spectacle lenses along the line of sight of their eyes, and unwittingly hit on an ingenious way of seeing faraway objects as though they were much closer.

Having said this, Denning appears to align himself with the opinions of many contemporary scholars in  attributing the invention of the telescope to a certain Hans Lippersheim (also known as Hans Lapprey), who was in possession of a simple telescope in 1608. On page 5-6 he refers to a critical piece of research carried out by the professional astronomer, Dr. Doberck, who showed the Lippersheim had applied for a thirty year patent from the Dutch States, in exchange for an annual stipend:

“He solicited the States, as early as the 2nd of October 1608, for a patent for thirty years, or an annual pension for life, for the instrument he had invented, promising then only to construct such instruments for the Government. After inviting the inventor to improve the instrument and alter it so that they could look through it with both eyes at the same time, the States determined on the 4th October, that from every province one deputy should be elected to try the apparatus and make terms with him concerning the price. The committee declared on the 6th October that the invention useful for the country, and they offered the inventor 900 florins for the instrument. He had at first asked 3000 florins for three instruments of rock crystal. He was then ordered to deliver the instrument within a certain time, and the patent was promised him on the condition that he kept the invention secret. Lapprey delivered the instrument in due time. He had arranged it for both eyes, and it was found satisfactory; but they forced him, against the agreement, to deliver two other telescopes for the same money, and refused the patent because it was evident that already several others had learned about the invention.”

pp 5-6

Denning proceeds form here to give an excellent overview of the unwieldy non-achromatic telescopes devised by Huygens, Hevelius, Cassini and Campani, amongst others, who ground and mounted lenses up to 8 inches in diameter with enormous focal lengths (up to 212 feet in focal length) yet all still delivering powers of 150 diameters or less. From here, Denning discusses the development of the much more convenient reflecting telescopes – the Gregorian, Cassegrain, Newtonian and other compound designs – and the problems associated with the construction of metallic mirrors fashioned from speculum metal (an alloy of copper, tin and small amounts of arsenic and/or antimony), which tarnished quickly and were exceedingly heavy in large apertures.

The author also discusses the origin of the Herschelian reflector, which involved tilting the primary mirror so that it reached a focus at the side of the tube without the requirement for a secondary flat mirror. The design, so Mr. Denning informs us, dates to 1728, when Le Maire first presented it to the French Academie des Sciences. Herschel adopted the design to increase the telescopes space penetrating power (light grasp) since it avoided a second reflection and hence saved more light that would otherwise have been lost with the addition of a second mirror. But such a design could not deliver the ‘defining power’ (image quality) of a conventional Newtonian. This is the principal reason why Herschel’s major work on the study of the planets and double stars were conducted with smaller Newtonian reflectors which were much more easy to operate and afforded the greatest degree of ‘mileage’ under the starry heaven.

Denning chronicles the growth in telescopic aperture throughout the 19th century, discussing such telescopes as the 6 foot aperture speculum built by the Third Earl of Ross as well as those used by Lassell and the great Melbourne telescope, which housed a 4-foot diameter (48 inch) speculum metal mirror with a focus of 28 feet. The latter telescope (produced by Howard Grubb of Dublin) was found to have poor defining power but Denning seems to lay the blame squarely with the shoddy mechanical set up of the instrument and not the optician.

The chapter ends with a discussion of the invention of the achromatic doublet by Chester Moor Hall (1729) and John Dollond and its development by Joseph von Fraunhofer, culminating with the creation of the sensational Dorpat Refractor of 9.5 inch aperture, and its state-of-the-art German equatorial mount, which ushered in the age of astrophysics.

Throughout the 19th century, astronomers began to build larger and larger refractors, first in Europe and then in North America, housed in magnificent domes that opened on every clear night to advance our knowledge of the heavens, and culminating with the Great Lick refractor of 36-inch aperture atop Mt. Wilson, California, which saw first light just three short years before the publication of Denning’s book. And while the author was aware that still larger refractors would surely come into existence, he seems more interested in a new technological advance in the production of parabolic mirrors for Newtonian telescopes; enter the silver-on-glass-reflector.

Beginning on page 14 and continuing on page 15, Denning describes the exciting work of the French physicist Jean Bernard Léon Foucault (1819-1868), who published a valuable memoir in which he described an ingenious new method of parabolising a glass disk followed by the deposition of a thin layer of silver upon its surface, and which exhibited much higher reflectivity than metal. It marked the end of the employment of speculum metal in telescope mirrors and ushered in a new age which promised to revolutionise both amateur and professional astronomy.

What is more, Denning informs us that Foucault developed lab-based methods of testing the accuracy of the parabolic surface in such a way as to render traditional testing methods – which involved time consuming and labour intensive trials under the stars – unnecessary. The customer could be assured of the quality of the mirror without it ever having being tested under the stars.

Denning writes:

Silver on glass mirrors immediately came into great request. The latter undoubtedly possess a great superiority over metal, especially as regards light gathering power, the relative capacity according to Sir John Herschel being as .824 to .436. Glass mirrors have also the advantage in being less heavy than those of metal. It is true that silver film is not very durable, but it can be renewed at any time with little trouble or expense.

pp 15.

Mr. Denning gives high praise to two British silver-on-glass mirror makers; George Henry With (1827-1904) of Hereford and George Calver (1834-1927) of Chelmsford, whose reflecting telescopes, ” were found nearly comparable to refractors of the same size.” pp 15.

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Author’s note: Modern scholarship seems to have converged on the name “Lippershey” as one of the earliest constructors of the telescope. Denning refers to the same man as “Lipperheim”. I was once reliably informed that the same chap should correctly be referred to as “Lipperhey”. After attempting to introduce this new nomenclature for a book I wrote, my editor returned it to “Lippershey” lol.

It is amusing that Denning referred to Galileo as “Galilei” to conform with the use of the surname in reference to individuals. Evidently, he thought it odd, which it most certainly is in retrospect.

Some memes are hard to shake.

Denning also points out that the great American refractors had recently employed powers of 3300 diameters in the resolution of the tightest double stars.

Denning was himself a convert to reflectors, after enjoying a fine 4.5 achromatic ( probably of f/15 relative aperture)  for a few years with which he carried out extensive solar work – a job ideally suited to the smaller refractor. In the end though, he sold that telescope in order to purchase a 10-inch With-Browning reflector in 1871 (when he was 23 years old) pictured on page 77 of the book. This telescope, so Denning will inform us, proved far more powerful than his former instrument. Indeed, Telescopic Work for Starlight Evenings is a distillation of twenty years of observations conducted with this same telescope.

The image below, kindly provided me by Denis Buczynski, a prominent member of the BAA, shows a 9.25 inch With-Browning (used by T.W. Webb) on a more sophisticated With-Berthon equatorial mount. But it serves our purposes well in illustrating the working dimensions of the telescope.

Denis Buczynski inspects the With/Berthon reflector ( BAA# 83) at his home in Lancaster.

Denis Buczynski inspects the With/Berthon reflector ( BAA# 83) at his home in Lancaster.

 

 

 

 

 

 

 

 

 

 

The image below pictures Denning beside his 10-inch.

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

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

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Chapter II: Relative Merits of Large and Small Telescopes

Covering pages 20 through 37.

Were it not for the vast sea of air that hugs our planet’s crust, the principles of telescopic astronomy would be clear and unequivocal; aperture rules, period. This is the reason for the spectacular success of the Hubble Space Telescope (HST), which, owing to its 2.4 metre primary mirror, has sent back the sharpest images of the heavens ever taken. It is also the reason why the widely anticipated replacement for HST, the James Webb Space Telescope, with its 6.4m segmented beryllium mirror, is expected to completely outclass it when it begins operations in 2018.

Down here on terra firma, the situation is rather more complicated. While there is no substitute for aperture if one wishes to pursue faint fuzzies, there is a great deal of anecdotal evidence that there exist practical limits on aperture in the pursuit of the finest lunar and planetary images. In a nutshell, although larger apertures offer the potential to see finer details, the atmosphere through which the amateur observes, often limits or even negates those advantages. Denning was arguably the first astronomer to raise awareness about this important topic and it was based upon his exceptional experience with instruments of all sizes, as well as his voluminous correspondences with the most active astronomers around the world.

Denning begins the chapter by discussing the rise in the number of large observatory- class instruments that had come to the fore during his lifetime and in past generations. Yet all the while he says:

There are some who doubt that such enormous instruments are really necessary, and question whether the results obtained with them are sufficient return for the great expense in their erection.

pp20

After discussing the realities of large telescopes, including their housing in an observatory, their mounting and maintenance, Denning extols the virtues of smaller instruments and alludes to a quality this author has previously referred to in the past as ‘mileage’:

…..small instruments involve little outlay, they are very portable, and require little space. They may be employed in or out of doors, according to the inclination and convenience of the observer. They are controlled with the greatest ease, and seldom get out of adjustment. They are less susceptible to atmospheric influences than larger instruments, and hence may be used more frequently with success and at places by no means favourably situated in this respect. Finally, their defining powers are of such excellent character as to compensate in a measure for feeble illumination.

pp 20-21

Denning begins with the telescopes of Sir William Herschel. Concerning his 4-foot reflector erected at Slough in 1789, he states that although Herschel discovered two of the inner satellites of Saturn shortly after the instrument was constructed, little else was achieved with it. Denning claims that Herschel much preferred the convenience of a smaller instrument – a 18.5 inch speculum of 20 foot focus in performing his famous sweeps for nebulae. Indeed the 4 foot telescope quickly fell into comparative disuse and his son, Sir John Herschel, had it sealed up for good on New Year’s Day, 1840. For defining power, Denning asserts that the great astronomer allegedly preferred instruments of much smaller size:

He found that his small specula of 7 foot focus and 6.3-in, aperture he had “light sufficient  to see the belts of Saturn completely well, and that here the maximum of distinctness might be much easier obtained than where large apertures are concerned.”

pp 21.

Following on from this, Denning discusses the Great 6-foot aperture telescope erected by the Third Earl of Rosse in Parsonstown (now Birr, Co. Offaly), Ireland. By 1891, this telescope had already been in service for 46 years and thus might provide insights into its relative utility. Denning concedes that it had done important work on elucidating the spiral morphology of many nebulae, M51 being perhaps the finest example. What follows is a fascinating overview of how it behaved. The satellites of Mars had eluded its grasp for three decades, until finally, in 1877, the outer moon, Deimos, was glimpsed twice, yet even then there was so much glare from the planet that no accurate measurements of its orbit were forthcoming. With Jupiter too, its enormous aperture was apparently of little advantage. This seems to be confirmed by a series of drawings made by William Parson’s son, Laurence (1840-1908), in the year 1873, and reproduced on page 128 in Thomas Hockey’s book, Galileo’s Planet: Observing Jupiter Before Photography. They reveal no more detail than could be obtained in a telescope ten times smaller.

Further insight into the efficacy of the Leviathan is gleaned from comments made by the Irish physicist, G.J. Stoney (1826-1911), who regularly used the instrument and who described his impression of γ2 Andromedae in a note made in 1878:

“The usual appearance [ of γ2 Andromedae ] with the best mirrors was a single bright mass of blue light some seconds in diameter and boiling violently.” On the best nights however, “the disturbance of the air would seem now and then suddenly to cease for perhaps half a second, and the star would then instantly become two very minute round specks of white light, with an interval between which, from recollection, I would estimate as equal to the diameter of either of them or perhaps slightly less. The instrument would have furnished this appearance uninterruptedly if the state of the air had permitted.

pp 23

Self evidently, it was not the optical quality of the mirror that was at issue but the environment in which it was placed. This was corroborated by a later observer in charge of the Leviathan, a one Dr. Boeddicker, active during the 1880s, who claimed that on a first class night, the amount of lunar detail seen with the giant mirror was “simply astounding.” We also learn that powers no higher than 600 diameters could be pressed into service, with occasional references to higher powers (1000x).

Denning then considers the work of William Lassell, who fashioned a number of large specula with which he discovered the two large satellites of Uranus; Umbriel and Ariel, independently co-discovered Hyperion, a faint satellite of Saturn and, just 17 days after the discovery of Neptune, its brightest moon, Triton (this name was not referred to by Denning as it was not formerly bestowed upon until a second Neptunian satellite, Nereid, was discovered in 1949).

Though Lassell, together with his assistant Mr. Marth, discovered a large number of nebulae from the sun drenched Mediterranean Island of Malta with his largest telescope of 4 foot aperture, Denning points out that it was with his 2 foot instrument that Mr. Lassell made all his planetary discoveries. Indeed, in 1871, Lassell wrote:

“There are formidable, and, I fear, insurmountable difficulties attending the construction of telescopes of large size…..These are primarily the errors and disturbances of the atmosphere and the flexure of the object-glasses or specula. The visible errors of the aperture are, I believe, generally in proportion to the aperture of the telescope…..Up to the size [referring to an 8in. O-G] in question, seasons of tranquil sky may be found where its errors are scarcely appreciable; but when go much beyond this limit (say to 2 feet and upwards),both these difficulties become truly formidable.”

pp 24.

That being said, Lassell also concluded that when conditions were fine, the advantages of aperture were clear for all to see. Concerning his largest telescopes he said:

“Nothwithstanding these disadvantages, they will, on some heavenly objects, reveal more than any small ones can.”

pp 24.

The chapter continues with Denning providing still more anecdotal evidence for the relative merits of large and small telescopes. Next in line, we hear about the 24.8 inch Cooke refractor erected by a well-to-do gentleman at Gateshead, England, which, despite its intimidating size, proved to have a ”singularly barren record”;

The owner of this fine and costly instrument wrote the author in 1885: “Atmosphere has an immense deal to do with definition. I have only had one fine night since 1870! I saw then what I have never seen since.”

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Author’s note: The Gateshead debacle is a particularly poignant story that has value for contemporary amateurs. Showmanship has no place in astronomy! The chap who installed the telescope obviously gave paltry attention to the environment in which the instrument was erected. The same gentleman seems to have had only a casual interest in astronomy, with little or no real experience of how such instruments would likely perform. The local seeing rendered the great telescope still born. One cannot help but wonder how many amateurs have done likewise over the years. Before spending lavish amounts of capital on a telescope, field testing the site on which it is to be constructed or used is mandatory. This accounts for the relative success of the large American refractors atop Mount Hamilton, for example, and the Great Meudon Refractor outside Paris, the sites of which were thoroughly field tested prior to their erection.

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The chapter continues with Denning relating other reports carried out by astronomers located at various observatories throughout the world. At the Paris Observatory, Dr. M. Wolf gained intimate acquaintance with various instruments including a 47.2 inch silver-on glass reflector, and a variety of smaller instruments, including a refractor of 15 inch aperture and 15.7 inch silver-on-glass reflector. Wolf wrote Denning concerning his visual experiences with these instruments:

“I have observed a great deal with the two instruments (both reflectors) of 15.7 and 47.2 inches. I have rarely found any advantage in using the larger one when the object was sufficiently luminous.” M. Wolf also avers that a refractor of 15 inches and a reflector of 15.7 inches will show everything  in the heavens  that can be discovered by instruments of very large aperture. He always found a telescope of 15.7-inch aperture surpass one of 7.9 inches, but expresses himself confidently that beyond about 15 inches increased aperture is no gain.

pp 26

Denning then relates the findings of Professor Young, who was assigned to a number of refractors, the largest being of 23 inch aperture, at Princeton, who related the following:

“The greater susceptibility of large instruments to atmospheric disturbances is most sadly true; and yet, on the whole, I find also true what Mr. Clark told me would be the case on first mounting our 23-inch instrument, that I can  almost always  see with the 23-inch everything I see with the 91/2 inch under the same atmospheric conditions, and see it better- if the seeing is bad, only a little better, if good immensely better.”

pp 27.

Another notable report comes from Mr. Keeler, who gained extensive experience with a number of instruments of various aperture atop Mount Hamilton:

Mr. Keeler adds: “According to my experience, there is a direct gain in power with increase in aperture. The 12-inch equatoreal brings to view objects entirely beyond the reach of the 61/2 inch telescope, and details almost beyond the perception with the 12-inch are visible at a glance with the 36-inch equatoreal.”

pp 28.

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Author’s note: These testimonies help to establish the veracity of a certain notion, that, from a visual perspective at least, greater aperture is only advantageous when atmospheric conditions cooperate. The relative efficacy of a given instrument is strongly dependent on the environment in which it is housed. Thus, no contradictions are found between theory and experiment.

I am mindful that this discussion focuses primarily on instruments generally larger than those found in amateur hands, but in recent years there has been an attempt by some amateurs (salesmen?), zealous to promote premium refractors over other models, to cultivate the erroneous view that the former can ” punch through the seeing” better on account of their “higher optical quality.” This arose from a deliberate twisting of some theoretical work conducted by this author in conjunction with theorist, Vladimir Sacek (which dealt mostly with the defocus aberration and its effects in long and short focal length systems). Although it was conceded that a slight advantage may be conferred on such higher quality instruments, in general, the seeing error completely overwhelms any small gains conferred in this way. As a further note of proof, many modern reflecting telescopes have Strehl ratios at or above those exhibited by ED refractors** (as measured by their polychromatic Strehl ratios) and so, by implication, ought to “punch through the seeing” even more effectively. That this is not commonly reported (either historically or in the ‘legitimate’ contemporary literature) demonstrates the effect is largely fictitious and irrelevant to any serious discussion of this interesting topic.

** The reader will note that, of the mirrors tested, it was the mass produced ones – read “least expensive” – that exhibited the highest Strehl. This is just one of many emerging test results found by inquisitive customers. This author can personally vouch for the quality of these mass produced mirrors, having regularly employed a 203mm and 130mm Newtonian(made by SkyWatcher) in field work.

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We shall not dwell further with the ideas conveyed by Mr. Denning in this engaging chapter, save to say that he concluded that there must exist some optimised aperture combining the best of both worlds for work on average nights:

There is undoubtedly a certain aperture which combines in itself sufficient light-gathering power with excellent definition. It takes a position midway between great illuminating power and sharp definition on the other. Such an aperture must form the best working instrument  in an average situation upon ordinary nights and ordinary objects. M. Wolf fixes this aperture at about 15 inches, and he is probably near the truth.

pp 35.

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Author’s note: This author is in agreement with Denning’s general conclusion. Indeed, this topic was explored in relation to the efficacy of resolving double stars, where a 8-inch aperture was found to be optimal in one interesting analysis.

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Chapter III: Notes on Telescopes and Their Accessories

Covering Pages 38 through 65.

In this chapter, the Last Master discusses the best choices of telescope and accessories needed by the amateur who wishes to pursue a serious, long-term study  of the firmament and begins with some sage advice:

The subject of the choice of telescope has exercised  every astronomer more or less, and the question as to the best form of instrument is one which has occasioned  endless controversy. The decision is an important one to amateurs, who at the outset of their observing careers require the most efficient instruments obtainable at reasonable cost. It is useless applying to scientific friends who, influenced by different tastes, will give an amount of contradictory advice that will be very perplexing. Some invariably recommend a small refractor and unjustly disparage reflectors, as not only unfitted for very delicate work, but as constantly needing re-adjustment and re-silvering.*

Others will advise a moderate-sized reflector as affording wonderfully fine views of the Moon and planets. The question of cost is greatly in favour of the latter construction, and, all things considered, it may claim an unquestionable advantage. A man who has decided to spend a small sum for the purpose not merely of gratifying his curiosity but of doing really serviceable work, must adopt the reflector, because refractors of, say, 5 inches and upwards are far too costly, and become enormously expensive as the diameter increases. This is not the case with reflectors; which come within the reach of all, and may indeed be constructed by the observer himself with a little patience and ingenuity.

*My 10-inch reflector by With-Browning was persistently used for four years without being resilvered  or once getting out of adjustment.

pp 38-39

Denning emphasises the convenience of reflectors over equivalent aperture refractors and mentions the innovations of the new silver-on-glass telescope makers, who managed to decrease the focal ratio, allowing decent aperture and viewing comfort to be maximised. George Calver had already begun to make telescopes with focal ratios as short as 5 or 6, which are now ubiquitous and deservedly popular. Denning estimates that a 8-inch reflector is equivalent to a 7-inch refractor (referring to a long focus instrument) in relative light gathering power, but in terms of defining power, especially in relation to planetary observing, Denning considers them equally good at equal aperture.

Having had the pleasure of observing through some of the finest telescopes in England, Denning was in a unique position to offer sensible advice to his readers:

An amateur who really wants a competent instrument, and has to consider cost, will do well to purchase a Newtonian reflector. A 41/2-inch refractor will cost about as much as a 10-inch reflector, but, as a working tool, the latter will possess a great advantage. A small refractor, if a good one, will do wonders, and is a very handy appliance, but it will not have sufficient grasp of light for it to be thoroughly serviceable on faint objects. Anyone hesitating in his choice should look at the cluster about χ Persei through instruments such as alluded to, and he will be astonished at the vast difference in favour of the reflector….. When high magnifications are employed on a refractor of small aperture, the images of planets become very faint and dusky, so that details are lost.

pp 41-42

Later he elaborates on the relative effectiveness of reflectors and refractors:

To grasp details there must be a fair amount of light. I have seen more with 252 on my 10-inch reflector than with 350 on a 51/4 inch refractor, because of the advantage of the brighter image in the former case.

pp 49

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Author’s note: How refreshingly honest and insightful Mr. Denning is! Having owned and enjoyed a number of smaller refractors of apochromatic and long-focus achromatic pedigree over the years (of 5- and 6-inch aperture), they have all paled in comparison to a 8-inch f/6 Newtonian on virtually all objects (the Sun being a memorable exception), and yet cost many times less. Vanity formed a large part in this author’s recalcitrance to embrace the genius of Newtonian optics, but when given a fair chance (proper acclimation and accurate alignment of the optical train), the refractors left little to be desired. For some, it remains an inconvenient truth that a well executed, mass market 20cm f/6 reflector would wipe the floor with the finest 5-inch glass on Earth, but it is undoubtedly true.

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Mr. Denning is however, sympathetic to the casual observer and acknowledges the role a small refractor might play in the pursuit of happy adventures:

Out of door observing is inconvenient in many respects, and those who procure a telescope merely to find a little recreation will soon acknowledge a small refractor to be eminently adapted to their purposes and conveniences.

pp42

That being said, Denning is careful to qualify this statement with the following:

Those who meditate going farther afield, and taking up observations habitually as a means of acquiring practical knowledge, and possibly of doing original work, will essentially need different means. They will require reflectors of about 8 or 10 inches aperture; and if mounted in the open on solid ground, so much the better, as there will be a more expansive view, and a freedom from heated currents, which renders an apartment unsuited to observations, unless with small apertures where the effects are scarcely appreciable. A reflector of the diameter mentioned will command sufficient light grasp to exhibit the more delicate features of planetary markings, and will show many other difficult objects in which the sky abounds. If the observer is especially interested in the surface configuration of Mars and Jupiter he will find a reflector a remarkably efficient instrument. On the Moon and planets it is admitted that its performance is, if not superior, equal to that of refractors.  If however, the inclination of the observer leads him in the direction of double stars, their discovery and measurement, he will perhaps find a refractor more to be depended upon, though there is no reason to why a well mounted reflector should not be successfully employed in this branch.

pp 42-43.

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Author’s note: Denning’s commentary here resonates very strongly with this author’s field experience. In respect of double stars, the 8-inch Newtonian was found to be a more effective instrument than a custom-made 5″ f/12 classical refractor, though historically, and inch for inch, there is overwhelming evidence to show that the classical refractor is better suited to resolving binary systems to the limits imposed by their aperture. Indeed, for this exacting task, they remain primus inter pares.

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Mr. Denning feels the images of stars in refractors are better than reflectors:

As far as my own experience goes, the refractor gives decidedly the best image of a star. In the reflector, a bright star under moderately high power is  seen with rays extending right across the field, and these appear to be caused by the supports of the flat.

pp 43.

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Author’s note: The stellar images in refractors are indeed very pretty, the Fraunhofer diffraction rings being very subdued and sometimes quite invisible on stars of lesser glory. Newtonians show diffraction spikes around bright stellar luminaries, and brilliant planets like Venus present with a singularly peculiar aspect in a moderately large Newtonian.

A Cruciform Venus

A Cruciform Venus, as seen with a 8-inch f/6 Newtonian on the evening of Saturday April 25 2015.

While this is certainly the case, it is a subjective point. Having accustomed myself to viewing through Newtonians, I must confess to finding these difrraction spikes to be rather beautiful. And while they may bother some individuals, they do not degrade the image in any significant way and can be ignored or unlearned.

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The chapter continues with a brief discussion on telescope testing. Denning’s approach is very down to Earth in this regard. He recommends that one should always try before you buy, especially if the instrument is second hand. As for the tests themselves, Denning does not recommend the Moon, as it is “too easy,” there being too much wonderful detail on view to side track the observer. Instead he recommends turning the telescope on bright planets, especially Jupiter and Venus to assess its defining power. Elaborating on Venus, he recommends  viewing at dusk or dawn, preferably when the planet has reached a decent altitude. As the magnification is cranked up, the disk of the planet should remain ” beautifully sharp and white.” A good telescope ought to hold its definition as the power is increased, with only an enfeebling of light as the image is spread over a larger area. A lesser telescope will show a deterioration of definition under the same conditions, producing a “mistiness” which confuses the definition in a palpable manner. Nor can these errors be ‘focused out’.

Denning also recommends star testing on a second or third magnitude star, the high power image of which ought to be tiny, circular and free from other distortions. If colour is seen in a reflector, it is probably the eyepiece and not the telescope that is at fault, though he does not mention the effects of atmospheric refraction that can manifest itself if the object under scrutiny is at a low altitude. He is also careful to distinguish between atmospheric distortion and a bona fide optical fault. Testing even a first rate telescope on a bad night of seeing is sure to produce iffy results and so these tests ought to be carried out over several nights to be certain of where the problem lies. Denning also  mentions the intra- and extra-focal colours of the diffraction rings seen in well corrected achromatic refractors.

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Author’s note: It is interesting that Denning does not suggest double stars as a test of telescope optics, in sharp contradistinction to many of his contemporaries. In reality though, the resolution of double stars is not a particularly stringent test of optics, as even so-so telescopes will manage some tricky pairs. Such tests are more a measure of atmospheric seeing and transparency than anything else. The best tests are on bright planets, especially Jupiter, which can display a rich variety of low contrast details that may prove elusive in a lesser instrument and become beautifully manifest in a higher quality telescope.

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No matter how wonderful or impressive the telescope being employed, without a sturdy mount, its powers will be greatly compromised. Denning considers both alt-azimuth and equatorial mounting systems, favouring the latter for high resolution projects, although stressing that high quality work can be done with simple non-driven mounts. Mr. Denning estimates that with an undriven, altazimuth mount, roughly 50 per cent of the observer’s time has to be expended adjusting the telescope in order to keep the object centred in the field, particularly if one is examining an object at high magnifications. In the end though, he cautions that a determined individual can make do with very simple equipment, and, in time, the observer “will gain patience and perseverance which will prove a useful experience in the future.”

pp 55.

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Author’s note: Denning actually opted for simplicity over technical sophistication with his own telescope, a 10-inch With-Browning Newtonian. It was mounted on a good but sturdy alt-azimuth mount, equipped with slow motion controls. By all accounts the instrument was permanently exposed to the elements (as evidenced by comments he made on page 76), the optics and tube assembly covered over when not in use. Denning’s telescope was thus in a permanent state of acclimation with its environment. No cooling fans were used with the telescope, as they were not available at the time, and indeed, were never really necessary.

While some modern amateurs would balk at this modest setup, it pays to remind the reader that Denning established himself as a world authority on planetary observing – particularly Jupiter and Saturn and their satellite systems – contributing a great body of knowledge in the form of drawings and written descriptions of his observations.

That Denning chose this setup over something more sophisticated reinforces an old maxim, that the quality of the observer is far more important than the type of equipment employed, a maxim that resonates strongly with this author’s ethos. This is especially true today when the amateur can enjoy high-quality mass-market optics at very reasonable prices. Denning’s estimate of the time lost in active observing must be tempered by the fact that the oculars he employed had very much smaller fields than those enjoyed by amateurs today, many of which can cover several times the area of sky he would have routinely encountered, thus reducing the time needed for object centering and adjustment.

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It is in this chapter also that Denning advances a brief but most engaging commentary on eyepieces;

Good eyepieces are absolutely essential. Many object-glasses and specula have been deprecated by errors really originated by the eyepiece. Again, telescopes have not infrequently been blamed  for failures through want of discrimination  in applying suitable powers. A consistent application of powers, according to the aperture of the telescope, the character of the object, the nature of the observation, and the atmospheric conditions prevailing at the time, is necessary to obtain the best results.

pp 46.

Denning describes the three most common oculars available to amateurs in his day: the negative, or Huygenian, the positive, or Ramsden, both of which had narrow fields of view and worked best at large relative apertures. he also mentions the Kelner, which afforded much wider fields of view (typically 40 or 50 degrees) for deep sky viewing and decent definition at relative apertures at f/6 and higher. Mr. Denning is sceptical of the claims of some telescope makers and users who have stated that their telescopes can bear powers of up to 100 per inch of aperture:

Telescopes are sometimes stated to bear 100 to the inch on planets, but this is far beyond their capacities even in the best condition of air. Amateurs soon find from experience that it is best to employ those powers that afford the clearest and most comprehensive views of the particular objects under scrutiny. Of course, when abnormally high powers are mentioned in connection with an observation, they have an impressive sound, but this is all, for they are practically useless for ordinary work. I find that 40, or at most 50 to the inch, is ample, and generally beyond the capacity of my 10-inch reflector.

pp 47

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Author’s note: Better oculars were invented in the mid to late 19th century, particularly the Plossl and orthoscopic, but owing to the greater number of un-coated elements, they were not commonly employed by amateur astronomers in Denning’s day. In respect to his comments regarding the 100x per inch claims by some observers and telescope sellers, this was a reasonable conclusion to draw, as one finds from experience that such high powers are indeed disadvantageous to delivering the best planetary images, especially in moderate and large aperture telescopes. Denning finds that 40-50x per inch of aperture to be the maximum upper limit for the vast majority of applications, and this remains true to this day. Indeed, we find that Denning commonly employed a power of 252 diameters on his 10-inch Newtonian in pursuing his studies of the bright planets, corresponding to ~ 25x per inch of aperture, in agreement with the recommendations of the majority of planetary observers even today. Indeed, it is only in the pursuit of the most difficult double stars and small planetary nebulae that higher powers are found to be useful, and only on the best nights.

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After these comments, Denning shares with us the details of a curious practice, apparently popular with dedicated observers for at least a century; using a single lens as an eyepiece:

A great advantage, both in light and in definition, results in the employment of a single lens as eyepiece. True, the field is very limited, and, owing to the spherical aberration, the objects so greatly distorted near the edges that it must be kept near the centre, but, on the whole, the superiority is much evident.

pp 47

Mr. Denning informs us that some distinguished observers, such as the Reverend William Rutter Dawes and Sir William Herschel had also noted an improvement in light grasp and distinctness employing the same technique.

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Author’s note:

Though we take so much for granted today, with our high quality optical glass, free of striations and other artifacts, broadband multi-coatings and the like, the glass out of which these early oculars were constructed would surely have been inferior to even the ‘budget’ oculars we enjoy today. The complete lack of anti-reflection coatings would have generated ghost-images due to internal reflections, especially on bright objects, cutting down on contrast and definition of low contrast details. Adopting a singlet would have greatly reduced these effects at the expense of introducing horrid off-axis aberrations.

This author once experimented with a modern ‘ball eyepiece’, that is, a single, spherical eye lens, and while the definition at the centre of the field was very nice, off axis images were very badly distorted. In the end, it was considered more a novelty than a useful tool and has not been used since.

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Denning recommends that the observer acquire three eyepieces, corresponding to low, medium and high power, appropriately chosen to match the aperture of the telescope, and cautions that the magnifications they profess to deliver may not in fact be the values they generate. He offers a means of experimentally determining actual magnifications described on pages 49-50. Denning continues by discussing the curious custom adopted by some telescope makers of using magnifying power as a ‘sales pitch’. Surprisingly, Denning identifies the famous maker, James Short (1710-68), as the individual who originated this dubious consuetude, who made his fortune selling small Gregorian-type reflectors, and which has sadly endured at least for so-called ‘department store’ telescopes right up to the present day.

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An ornate, table top Cassegrain reflector by James Short, dating from the mid-18th century.

An ornate, table top Gregorian reflector by James Short, dating from the mid-18th century.

A curious aside: Denning owned a 4-inch Gregorian telescope by Watson, similar to the instrument shown above, which, although over a century old at the time, had speculum metal mirrors that were still in good condition.

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The importance of observing in comfort (pages 53-54) is a subject very close to Denning’s heart and, accordingly, he stresses the importance of using a chair while observing and even mentions some innovations made by amateurs published in the English Mechanic. He also reveals that for objects located high overhead, a small step ladder was found to be very useful  with his 10-inch Newtonian. Comfort is of paramount importance in gaining the maximum enjoyment from an observing experience and can even make the difference between seeing something and not at all.

Beginning on page 55 and ending at the top of page 57, Denning remarks on the ‘character’ of the observer. Variations in visual acuity account for some of the discrepancies reported by observers, as well as their level of experience. Some individuals will see more than others. Historically, these differences have sometimes led to controversy:

….as a rule, amateurs should avoid controversy, because it rarely clears up a contested point. There is argument and reiteration, but no mutual understanding or settlement of the question at issue. It wastes time, and often destroys that good feeling which should subsist amongst astronomers of ever class and nationality…. paltry quibblings, fault finding, or the constant expression of negative views, peculiar to sceptics, should be abandoned, as hindering rather than accelerating the progress of science….. There are some men whose reputations do not rest upon good or original work performed by themselves, but rather upon the alacrity with which they discover grievances and upon the care they bestow in exposing trifling errors in the writings of their non-infallible contemporaries.

pp 56

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Author’s note: There is nothing new under the Sun, and Denning’s comments are as true today as the day they were written. We are all fallen, all of us wretched, and in need of redemption. And yet, we can rise above it all and do great things. Men vainly look to the heavens in search of people among the stars, yet the only ‘aliens’ we will ever encounter are our neighbours. We need to get on with each other.

Denning himself was the subject of controversy concerning some of his ideas on meteor radiants. He held some erroneous views but was bitterly attacked by some of his contemporaries, just to ‘prove’ that they were ‘right’ and he was ‘wrong.’ They wounded him deeply. This is likely one of the reasons why he withdrew from public life at the height of his career.

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On page 58, Denning discusses the practice of stopping down, i.e. the act of deliberately reducing the effective aperture by means of a ‘stop.’ The practice was sometimes done to increase the defining power of the telescope, which, for clarity, we shall equate with image sharpness, but the underlying reason for this was thought by some to be caused by blocking off a defective part of the object glass or speculum. Denning however, offers us another explanation; the atmosphere and its effects on the fielded aperture. While it is true that stopping down could mask a figuring error (more likely to occur at the edges of the objective), Denning’s own experiments seemed to favour the idea that large apertures can often benefit from stopping down on nights of poor or average seeing because smaller apertures are less affected by atmospheric turbulence than larger ones. He suggests that, for visual use, apertures of 18 inches and over can quite often benefit from an aperture stop of 16- or 14-inch stop. But he cautions that the practice is of little value in the case of moderate aperture;

With my 10-inch reflector, I rarely, if ever, apply stops, for by reducing the aperture to 8 inches the gain in definition does not sufficiently repay for the serious loss of light. But in the case of large telescopes, the conservation of light is not so important, and a 14-inch or 16-inch stop may be frequently employed on an 18-inch with striking advantage.

pp 58

In a curious note under the subtitle, Cleaning Lenses, Denning tangentially discusses some of the properties of silvered mirrors, in particular, the factors that may prolong the life of the thin silver layer. He notes that keeping the mirror dry is of benefit, as well as placing a protective cap over the optics when not in use. He claims that Calver was aware that some silvered glass mirrors held their reflectance longer than others and was related to the frequency with which the instrument was used and the environment in which it was fielded. Some mirrors held their reflectivity well for a decade or more, but this was apparently the exception rather than the rule. Intriguingly, he also states that the tarnish accumulated on silvered mirrors can work surprisingly well on lunar and planetary targets:

A mirror that looks badly tarnished and fit for nothing will often perform wonderfully well. With my 10-inch in a sadly deteriorated state I have obtained views of the Moon, Venus and Jupiter that could hardly be surpassed. The moderate reflection from a tarnished mirror evidently improves the image of a bright object by eliminating the glare and allowing the fainter details to be readily seen.

pp 60

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Author’s note: When silver tarnishes it generally leaves a tan coloured film owing to the formation of silver sulphide, which can indeed reduce the relectivity of the mirror, but the moderate deterioration Denning speaks of seemed to enhance his views of the Moon and bright planets. I believe that this can be attributed to a filter-like or ‘apodising’ effect. As this author has commented on elsewhere, filters work superbly well on moderate and large aperture telescopes owing to their ability to suppress glare and enhance the visual appearance of  subtle details that would otherwise be ‘washed out’ in the unfiltered image. This author has previously alerted readers to the benefits of employing a simple and inexpensive neutral density filter to improve the planetary images in large reflectors. More sophisticated filters, such as a polariser, also work very well in this regard. The Televue bandmate planetary filter was also found to work brilliantly on the author’s 8-inch Newtonian, which he employs routinely  to observe Jupiter. Filters are capable of adding a whole new dimension to the art of visual observing; an effect serendipitously ‘discovered’ by Denning.

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The remaining pages of this chapter are devoted to miscellaneous topics, including dewing up and cooling down of telescope optics, the celestial globe, presumably a fore-runner of the modern planisphere, the utility of opera glasses and finally a brief description of a new type of observatory showing up the length and breadth of the country; the Romsey. Unlike the all-brick, monolithic, cathedral-like domes housing the great refractors of the day, the Romsey offered a much more economical means of housing one’s telescope and keeping all one’s ancillary equipment in a single place.

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Chapter IV Notes on Telescopic Work

Covering pages 66 through 86

In this invaluable chapter, Mr. Denning provides a distillation of his practical experience in the field. He begins by suggesting that the would-be astronomy enthusiast gain some background knowledge of the objects he/she wishes to devote time to. This can be achieved by reading up on the general descriptions provided by trusted authorities in the field. But theory ought to be a guide and not an absolute means to an end, for Denning seems to value practical knowledge over that learned in books:

An observer should take the direction of his labours from previous workers, but be prepared to diverge from acknowledged rules should he feel justified in doing so from his new experiences.

pp 68

Denning feels that the observer ought to prepared for a night of observing, by making up a suitable list of objects he/she wishes to study. It need not be long and over-elaborate, nor should such a list be over ambitious.  A few objects studied well is far better than several dozen casually visited.

When no such preparation is made much confusion and loss of time is the result. On a cloudy, wet day, observers often consider it unnecessary to make such provision and they are taken at a great disadvantage when the sky suddenly clears. A good observer, like a good general, ought to provide, by proper disposition of his means, against any emergency. In stormy weather, valuable observations are often permissible if the observer is prompt, for the definition is occasionally suitable under such circumstances.

pp69

Denning estimates that the British climate offers about 100 hours of exceptional seeing per year, considerably more than is commonly believed today, but these are not confined to just a few nights, but occur sporadically over the course of the weeks and months, for he says that a night might start out with decidedly mediocre seeing only to be found to be considerably improved just a few hours later.

Denning claims that an east wind is often detrimental to viewing high resolution targets, but does not consider this to be an absolute. He differs from the general opinion expressed by contemporary astronomers in claiming that windy weather can often bring very good seeing:

I have sometimes found in windy weather after storms from the west quarter, when the air has become very transparent, that exceptionally sharp views may be obtained; but unfortunately, they are not without drawbacks, for the telescope vibrates violently with every gust of wind and the images cannot be held long enough for anything satisfactory to be seen.

pp 69

Denning mentions the favourable conditions that often attend hazy skies:

Calm nights when there is a little haze and fog, making the stars look somewhat dim, frequently afford wonderfully good seeing….. The tenuous patches of white cirrus cloud, which float at high altitudes will often improve definition in a surprising manner, especially on the Moon and planets.

pp 69.

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Author’s note: Denning’s knowledge was gained actively, in the field, more so than any of his contemporaries, for how else could he provide such extraordinary (and mostly correct) insight? Denning’s telescope was in a constant state of preparedness, as it was permanently fielded in the open air. He was thus ready to take advantage of any change in the weather that may have come about and use it to his advantage. Such knowledge cannot be learned from a book. That Denning entrusted experience over theory resonates well with this author’s own findings, especially in relation to double stars, where striking discrepancies between field observations and the prognostications of individuals posing as ‘theorists’ have been uncovered. Indeed, in some of these cases, the differences between theory and experiment have been totally irreconcilable.

Iustitia, iustitia, iustitia!

Beware of theorists posing as observers!

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Mr. Denning next discusses vision and its relation to telescopic observation. He concedes that there is much inter-individual variation among the visual acuity of individuals, with some displaying remarkable vision and others seeing much less. He mentions a one Dr. Kitchiner, who claimed that the eye of a dedicated telescopist aged 47 is as much impaired as an ordinary individual aged 60! Denning is somewhat sceptical of that claim stating that, “the Doctor’s opinion is not generally confirmed by other testimony, the fact being that the eye is usually strengthened by special service of his character.”

Further, he states:

Before the observer may hope to excel as a telescopist it is clear that a certain degree of training is requisite. Many men exhibit very keen eyesight under ordinary circumstances, but when they come to the telescope are hopelessly beaten by a man who has a practised eye. On several occasions the writer was most impressed with evidences of extraordinary sight in certain individuals, but upon being tested at the telescope they were found very deficient, both as regards planetary detail and faint satellites.Objects which were quite conspicuous to an experienced eye were totally invisible to them.

pp 71

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Author’s note: Denning’s comments agree with the experiences of this author. On many occasions over the years, I have attempted to show my students some of the delights of the second heaven, only to discover that, although they have decidedly better eyesight than my own, were unable to ‘see’ the duplicity of test double stars, plainly seen with my own eyes. Only after pointing it out and after prolonged scrutiny did they come to ‘see’ what was plainly visible. The same is true of the Great Red Spot.  Experience is a far better tool than raw visual acuity. Seeing is most definitely an art that must be learned.

I believe this also has implications for those that have derided the classical achromat, despite an enormous body of evidence demonstrating that their users (who’s eyes were trained) saw far more than what is commonly reported in the contemporary ‘literature.’ Indeed they appeared to have seen things that still largely elude the majority of self-proclaimed veterans.

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On page 72-73, Mr. Denning stresses the importance of note making. The content of these notes need not be elaborate, just a few salient points about the date, time and seeing conditions, the instrument fielded and some brief written details on the objects observed. Denning recommends that such notes be made as close to the time of observation as possible. “If the duty is relegated to a subsequent occasion,” he says, “it is either not done at all or done very imperfectly.”  Something ‘trivial’ recorded on an earlier date may turn out to be very important at a later date.

Denning also recommends sketching what one sees at the telescope, even if the would be observer is not skilled in such activities. They need not be works of art but simply show the ‘definite’ features of the object under scrutiny. With time, the note maker/sketcher becomes a “draughtsman:”

My own plan in sketching at the telescope  is to first roughly delineate  the features bit by bit  as I successively glimpse them, assuring myself, as I proceed, as to the general correctness in outline and position, then, on completion, I go indoors to a better light and make copies while the details are still freshly impressed on the mind.

pp 74

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Author’s note: It is a sad state of affairs that the noble art of note making is in decline; perhaps terminally. Many amateurs do not make any notes of any description. More’s the pity, for notes provide a means of assessing progress over time, and form the bedrock of an amateur’s experience under the starry firmament. They are an integral part of the culture of amateur astronomy and can prove invaluable in resolving issues that sometimes appear contradictory, especially if one is viewing through different instruments at different times. An observer without notes is liable to make the same mistakes over and over again.

An observer without notes has no past.

Sketching is also an enjoyable and invaluable way of preserving information and when conducted over a long period of time, can prove to be of vital importance, especially if one records something novel. There is no ‘right’ or ‘wrong’ way to sketch. Denning preferred to sketch the basic features of his subjects at the telescope, while refining them indoors a short time afterwards. Others choose to scrutinise the object intently, committing to memory all the detail one can capture before returning indoors to perform the sketch. Find the method that works best for you.

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In a section called “Friendly Indulgences,” Denning recognises the need for outreach and to be gracious to friends and the curious passerby, who express an interest in viewing an astronomical object. But in the end, he feels that there is a fine line between getting on with one’s observing and being a “showman.” One comes away with the feeling that he was, for the most part, a solitary observer, who was happy in his own company and would rather get on with things than engage in some lengthy discussion with someone else while the sky remained clear:

Of course it is the duty of us all to encourage a laudable interest in the science, especially when evinced by neighbours or acquaintances; but the utility of an observer constituting himself a showman, and sacrificing many valuable hours which might  be spent in useful observations, may be seriously questioned. The weather is so bad in this country that we can ill spare an hour from our scanty store.

pp 74.

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Author’s note: One cannot help but wonder what Denning would have thought of the star parties amateurs attend these days. I suspect he would have kept well away from them. While star parties can be fun and provide a means of looking through various kinds of telescope to assist making a decision on a future purchase, our hobby is still, by and large,  a solitary passtime. We must remember that for every lion among us there is also a leopard.

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Denning discusses the realities of open air observing, wittily commenting that a shiny new telescope tube exposed to the elements of nature will soon lose its “smart and bright appearance”, although the views will remain as good as they always were. It is here also that the forgotten Bristolian reveals his great love affair with the heavens, providing vivid descriptions of the physical conditions he had to endure night after night. Because he remained a bachelor all his life and thus, had no dependants, his life could be best be likened to that of a monk, wedded as it were to his astronomical investigations. As a dedicated meteor observer, he spent endless hours on every clear night recording their brilliant tracks across the sky. This kind of work is not for the faint hearted, especially in the cold of winter. Denning describes his lot vividly:

Night air is generally thought to be pernicious to health; but the longevity of astronomers is certainly opposed to this idea. Those observers who are unusually susceptible to affections of the respiratory organs must of course exercise extreme care, and will hardly be wise in pursuing astronomical work out of doors on keen, wintry nights. But others, less liable to climatic conditions, may conduct operations with impunity and safety during the most severe weather. Precautions should always be taken to maintain a convenient degree of warmth; and for the rest, the observer’s enthusiasm must sustain him. A “wadded dressing gown” has been mentioned as an effective protection from cold.  I have found that a long, thick overcoat, substantially lined with flannel, and under this a stout cardigan jacket, will resist the inroads of cold for a long time. On very trying nights, a rug may also be thrown over the shoulders, and strapped round the body.  During intense frosts, however, the cold will penetrate (as I have found during prolonged watches for shooting stars) through almost any covering. As soon as the observer becomes uncomfortably chilly, he should go indoors and warm his things before a fire.

pp 75.

After relating many humorous stories about finding wee beasties taking up residence inside his telescope tube, Denning returns to more pressing matters, emphasising that an observer eager to discover something of importance must necessarily be a person of method and perseverance and not to divest too much importance to his instruments;

A skilled workman will do good work with indifferent tools; for after all it is the character of the man that is evident in his work; and not so much the resources which art places in his hand.

pp 80

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Author’s note: The old adage is true: a bad workman always blames his tools. Today, we are blessed to have vastly superior ‘tools’ to anything Mr. Denning could have dreamed of. And yet, all the while, we seem to want  more and more. Fortunate indeed is the man who is happy with his tools!

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In the final pages of this interesting chapter, Denning discusses the potential of photography to revolutionise the science of astronomy. His opinions are brief but he was essentially correct about its growing prowess, but since very few amateurs had the means of conducting photographic studies of the heavens at that time, he does not dwell on the topic.

The author encourages his readers to follow the astronomical literature, and recommends all the greats of the age including the Reverend T.W Webb’s,Celestial Objects for Common Telescopes, Chamber’s Descriptive Astronomy and Noble’s, Hours with a 3-Inch Telescope, as well as more specialised texts. He also encourages his readers to consult practical periodicals of the day, especially the English Mechanic, Nature and Knowledge. 

Denning encourages those who live in towns and cities to get out and do some observing, explaining that the conditions can be quite good, especially for viewing the Moon and the planets. He mentions that smoggy conditions may actually aid in bringing out detail on the planetary bodies:

I have frequently found planetary markings very sharp and steady through the smoke and smog of Bristol. The interposing vapours having the effect of moderating the bright images and improving their quality.

pp 81.

He ends this chapter on an enthusiastic note:

A telescope may either be employed as an instrument of scientific discovery and critical work, or it may be made a source of recreation and instruction. By its means the powers of the eye are so far assisted and expanded that we are able to conceive of the wonderful works of the Creator than could be obtained in any other way.

pp 86.

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Author’s note: The population of Bristol, where Denning lived for most of his life, quintupled during the 19th century, reaching 330,000 by 1901. The burning of coal would have been the main source of energy driving commerce and heating households, and so smog would have been a common phenomenon especially during still winter nights in the city.

Denning yet again mentions the beneficial effects of dimming the image as regard gleaning more defining power from planetary bodies. I cannot help but think that were he alive today, he would have been an enthusiastic proponent of filters in the planetary astronomy.

Unbridled enthusiasm distinguished Denning from many of the classic authorities of his day. His tone was approachable, unpretentious and reassuringly upbeat. What he saw through his telescope was his reaction to the natural wonders created by the Living God, who placed these things in heaven so that we might marvel at them and be reminded of His omnipotence. In this capacity, he was a kindred spirit, who saw no conflict between scientific investigation and his personal faith.

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Chapter V: The Sun

Covering pages 87 through 112

We now begin to explore the late 19th century knowledge of the heavenly bodies, one by one, beginning with the Sun. As a guide, this author will bring to bear his experiences with a telescope not too dissimilar to Denning’s own; a 8″ f/6 Newtonian on a modern alt-azimuth mount, which has given him wondrous views of the firmament.

Jupiter as it appeared at 10:00pm local time on the evening of May 5, 2016. Magnification 200 diameters.

Jupiter as it appeared at 10:00pm local time through a 8″ f/6 Newtonian on the evening of May 5, 2016. Magnification 200 diameters.

 

 

 

 

 

 

 

 

 

 

The opening pages of this chapter discuss basic solar facts, as true today as they were in Denning’s time. The Sun, we learn, has a mean distance from the Earth of about 92,900,000 miles, computed from a solar parallax of 8.8″, and a diameter of 866,000 miles. Interestingly, Denning provides a series of micrometer measures (pp 88) of the solar disk diameter, showing that it varies from 32 minutes 66 seconds at the end of December, to 31 minutes 32 seconds at the end of June. This reflects the slight ellipticity of the Earth’s orbit, carrying our planet slightly closer to the Sun in mid-winter in the Northern Hemisphere  and a little further away in mid-summer.

Denning relates the fact that the most conspicuous feature of the solar disk – sunspots – were likely seen throughout antiquity, and among observers from a number of civilizations. The earliest account offered by the author dates to 188AD. These spots were seen by the naked eye through dense fog, most commonly at sunrise and sunset. Denning himself speaks of observing four large spots (pp 89) on a foggy autumnal evening in 1870, just as the Sun was setting. He claims that if these spots are bigger than about 50″, they should be picked up by the average eye.

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Author’s note: Although a curious visual phenomenon, this author strongly advises that the reader not look at the Sun even in the very foggy conditions described above. Many a tyro has damaged his/her eyes in doing so.

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Denning is reluctant to attribute the telescopic ‘discovery’ of sunspots to any one individual but mentions, in particular, various early telescopists including, Fabricius, Galilei, Harriot and Scheiner, as claiming the limelight. He also corroborates later accounts by historians of astronomy, who claim that England’s Thomas Harriot saw these spots telescopically as early as December 8, 1610:

“The altitude of the Sonne being 7 or 8 degrees, and it being a frost and a mist, I saw the Sonne in this manner.”

pp 90.

He also mentions a drawing made by Harriot, showing three large sunspots. Thus, Denning was probably aware of Harriot’s early telescopic observations; possibly predating those made by Galileo Galilei.

The most common way in which observers in Denning’s day observed the Sun was to employ deeply coloured glass of various ‘depths’; either red or green, placed at the focal plane, together with a Herschel wedge, invented in 1830 by Sir John Herschel. Denning claims that red tinted glass is inferior to its green tinted counterpart:

The diagonal, by preserving a part only of the solar rays, which are transmitted by the object glass. This little instrument is comparatively cheap, and no telescope is complete without one.

pp 92.

Denning suggests that a small telescope, a refractor of 3- or 4-inch aperture, or a reflector of no more than 4-inches, are best employed in solar studies and recommends that larger instruments be stopped down to improve definition. He also mentions, owing to the great natural brilliance of the Sun, that unsilvered mirrors are perfectly adequate for obtaining good solar images.

With comfort and safety never being far from the mind of the author, Denning stresses that the solar observer be shaded from the Sun’s burning rays as much as is practical. He also recommends keeping the ‘solar telescope’ in the shade to ensure it does not induce the annoying thermals that can destroy high-definition features. As regard suitable magnification, he suggests that a power of about 60 and a field of view of just over half an angular degree is desirable to get a good ‘whole disk’ perspective. Higher powers can prove usual to gain better images of smaller features, though he does not recommend magnifications higher than about 150x. Once again, Denning mentions using a singlet eyepiece (presumably the field lens of a Huygenian ocular) in obtaining high power views yielding the highest definition.

Oddly enough, Denning gives scant mention to other methods of observing the solar disk, particularly by projecting the image onto a smooth, white surface. There is one reference made to this technique, appearing on page 93-94:

At Stonyhurst Observatory excellent delineations of solar phenomena are made; and the late Father Perry, who lost his life in the cause of science, thus described the method:- “On every fine day the image of the Sun is projected on a thin board attached to the telescope, and a drawing of the Sun is made, 101/2 inches in diameter, showing the position and outline of the spots visible.

pp 93-94

Solar projection techniques were used by the very earliest telescopists, including Galileo Galilei.

In a most curious account related on page 95, Denning describes the use of a primitive reticle scale, just a graduated piece of plane glass, mounted at the focal plane of a 4-inch Cooke refractor, borrowed from a friend, with which he was able to estimate the size of a large sunspot, observed on June 19, 1889. Using this technique he calculated that the real size of the spot was 27,000 miles! This technique could also be done using projection methods.

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Author’s note: Man and his numbers! How wonderful it is to be able to measure anything! Among other reasons, our heavenly Father gave us these powers so that we could project our imagination into realms hopelessly beyond the ability of our frail bodies to experience directly. Denning was no mathematician, of course, but he did have an excellent command of numbers, as we shall see in many other references explored later in the book.

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The chapter continues with discussions on various solar phenomena, beginning with the majesty of a solar eclipse, briefly describing their prediction (saros cycles) and rarity at any arbitrarily chosen location. On page 98, the aspects of a series of 12 partial solar eclipses as seen (or imagined) from England through the years 1891 to 1922, are reproduced. This is followed by an equally brief discussion on the sunspot cycle and how it may be followed by the amateur equipped with modest equipment.

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Another curious aside: In his younger years, Denning was a keen hunter of the hypothetical planet Vulcan, explaining why he had a particular interest in all things solar. Indeed, he helped organise coordinated searches for the planet among a number of English solar astronomers. Moreover, in Chapter IV, page 85, he made two lists of (I) ‘suspected objects to be erased’, and (II) ‘objects that in the future will add to our store’. Vulcan appears in the former list, suggesting that, at the time of writing of the book, he had firmly given up on the prospect of finding an intra-mercurial planet.

The quest for Vulcan reached fever pitch in Europe and across the United States during the late 19th century, bolstered by the work of mathematical (but myopic) astronomers of the ilk of (the arrogant) Urban Leverrier(1811-77), who uncovered a small, residual perihelion shift in the position of the planet Mercury, amounting to 43 arc seconds per century. Indeed a hitherto obscure physician and amateur astronomer, Edmond Modeste Lescarbault (1814-94), claimed to have observed such a planet in March 1869 at his private observatory in the picturesque village of Orgères-en-Beauce, in Northern France. Leverrier was happy to accept him as the discoverer and formally named the planet Vulcan – after the Roman god of fire – in March 1860, which circled the Sun every 19.7 days, at a distance of about 21 million kilometres from the solar surface. But soon, the astronomical community grew sceptical of Lescarbault’s sensational ‘discovery,’ claiming that such a world, even though as small as the Moon, would have been easily visible to many astronomers who had watched the Sun for many years.

By the time Denning penned his tome, most astronomers had dismissed the notion that a ninth planet, Vulcan, really existed, even though the reason for the measurable 43” per century perihelion shift of Mercury was not yet accounted for. The explanation had to wait until Albert Einstein formulated his epochal theory of general relativity in 1915, which perfectly accounted for the Mercury anomaly. Indeed, Einstein was to later write that his heart raced when his calculations exactly explained the planet’s sojourn through the curved space near the Sun. “For a few days,” he wrote, “I was beside myself in joyous excitement.”

All the while, I cannot help but think that Denning, in the exuberance of his youth, also searched for Vulcan with “joyous excitement.”

More on Vulcan here.

From pages 100-112, Denning goes on to describe, in considerable detail, the telescopic morphology of sunspots as well as their distribution on the solar surface. He provides an accurate an essentially modern value for the solar rotation period of ~25 days and 8 hours. It was also known to him that the rotation period varies with solar latitude, thus providing good evidence (like Jupiter, discussed later) for its essentially gaseous nature. On page 105, Denning presents a list of historically interesting astronomers and their estimates of the solar rotation rate from Cassini (1678) to Wilsing (1888), showing that such knowledge was known for nearly two centuries.

Denning displays his voluminous knowledge of solar phenomena in these closing pages of Chapter V, including the work of many astronomers – both contemporary and historical – as well as his some of his own detailed observations carried out with a 4-inch glass. This includes a discussion on solar faculae, prominences and historically significant eruptions, as well as some observational anomalies including spots noted at unusually high solar latitudes;

Mechain saw a spot in 1780 having a latitude of 401/3 degrees; in April 1826 Cappoci recorded one having 49 degrees of S. latitude Schwabe and Peters observed  spots 50 degrees from the equator. Lahire, in the last century, described a spot as visible of 70 degrees; but the accuracy of this observation has been questioned.

pp111.

Finally, on page 112, Denning provides a curious reference to a quantitative brightness differential between the solar limb and its centre, a measure previously unknown to this author:

In observing the Sun with a telescope the amateur will soon notice that the surface is far more brilliant in the central parts than round the margin of the disk. Vogel has estimated that immediately inside the edges the brightness does not amount to one seventh that of the centre.The difference is entirely due to the solar atmosphere, which is probably very shallow relatively to the great diameter of the Sun.

pp 112

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Author’s note: The Sun is, by and large, composed of a fourth form of matter called plasma. At temperatures in excess of a few thousand Kelvin, atoms break up to form a ‘soup’ of charged particles consisting of electrons, protons and an assortment of atomic nuclei. It is this moving plasma that generates the Sun’s prodigious magnetic field and all its associated phenomena.

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Chapter VI The Moon

Covering pages 113-136

Early in autumn, when the evenings are frequently clear, many persons are led with more force than usual to evince an interest in our satellite, and to desire information which may not be conveniently obtained at the time. The aspect of the Moon at her rising, near the time of the full, during the months of August, September, and October, is more conspicuously noticeable than at any other season of the year, on account of the position she then assumes on successive nights, enabling her to rise at closely identical times for several evenings together. The appearance of her large, ruddy globe at near the same hour, and her increasing brilliancy as her horizontal rays give way under a more vertical position, originated the title of “Harvest Moon,” to commemorate the facility afforded by her light for the ingathering of the corn preceeding the time of the autumnal equinox.

pp 113

It is with such wonderful prose that Denning opens his chapter on observing our closest neighbour in space. Denning was a man happy to be in the open air, either with telescope or with his unaided eyes, observing the grand spectacles of the heavens. In the proceeding paragraphs, he clearly outlines why the Moon is of such critical importance to life on Earth, in issuing the tides, for example, and stabilising the Earth’s climate. But he also notes its importance, since time immemorial, in human time keeping, as well as how its welcome light assisted the plight of navigators of the seven seas.

What follows thereafter are some basic physical facts about the Moon. For example, he states the apparent size of the Moon at apogee and perigee (29’21” and 33’5”, respectively), though he appears to have mistakenly stated these the wrong way round on page 114. The lunar diameter he quotes – 2160 miles – and its mean distance from the earth – 237,000 miles – are essentially those of the modern value.

Denning then launches into a general overview of the lunar regolith as seen through a good telescope;

When we critically survey the face of the Moon with a good telescope, we see at once that her surface is broken up into a series of craters of various sizes, and that some irregular formations are scattered here and there, which present a similar appearance to mountain ranges. The crateriform aspect of the Moon is perhaps the more striking feature, from its greater extent; and we recognise in the individual forms a simile to the circular cavities formed in slag or some other hard substances under the action of intense heat. In certain regions of the Moon, especially near the south pole, the disk is one mass of abutting craters, and were it not for the obvious want of symmetry in form and uniformity in size, the appearance would be analogous to that of a giant honeycomb. These craters are commonly surrounded by high walls or ramparts, and often include conical hills rising from their centres to great heights. While the eye examines these singular structures, and lingers amongst the mass of intricate detail in which the whole surface abounds, we cannot but feel impressed at the marvellous sharpness of definition with which the different features are presented to our view. It matters not to what district we direct our gaze, there is the same perfect serenity and clearness of outline. Not the slightest indication can be discerned anywhere of mist or other obscuring vapours hanging over the lunar landscape.

pp 114-115

Denning correctly states that the Moon is devoid of an atmosphere and probably doesn’t have water, in spite of the many ‘seas’ that adorn lunar maps. On page 115 through 116, Denning presents an explanation for why the Moon shows the same face toward the earth throughout its cycle (it is almost completely tidally locked) and presents the interesting phenomenon of libration, where the lunar countenance can show up to 59 per cent of its surface over the course of its earth orbit.  Denning also mentions the wonderful phenomenon of earthshine, the “ new Moon in the old Moon’s arms,”  and how the observers of old remarked that a waning Moon showed this earthlight more strongly than the new Moon.

The chapter continues by discussing the kinds of instruments best suited to lunar work, for the casual as well as the more serious observer:

A small instrument with an object glass of about 2 ½ inches will reveal a large amount of intricate detail on the surface of our satellite, and will afford the young student many evenings of interesting recreation. But for a more advanced survey of the formations, with a view to discover unknown objects or traces of physical change in known features, a telescope of at least 8 or 10 inches is probably necessary, and powers of 300 to 350, and more.

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Author’s note: Yet again, Mr. Denning dispenses sterling advice to the would-be student of the Moon that is entirely in agreement with all subsequent authorities on the subject. You’ll see more with a larger telescope and will be able to use higher powers to ferret out the finer details. Such advice appears to have been lost on a current subsection of amateurs who are willing to squander a veritable fortune for small refractors of very limited aperture. Such are the times we live in!

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On pages 118 and 119, Mr. Denning discusses the fascinating phenomenon of a lunar eclipse, their frequency and appearance, both telescopically and to the naked eye. Here we find some invaluable historical records of how the intensity of a total lunar eclipse varied from apparition to apparition, with references to observations conducted by astronomers dating back nearly nine centuries. While some total lunar eclipses were spectacularly bright, with a beautiful, coppery orb being clearly visible to the naked eye, at other times, the eclipsed Moon completely disappeared:

On May 5 1110, Dec.9, 1620, May 18, 1761, and June 10, 1816, our satellite is said to have become absolutely imperceptible during eclipse. Wargentin, who described the appearance 1761, remarks:- “The Moon’s body disappeared so completely that not the slightest trace of any portion of the lunar disk could be discerned, either with the naked eye or with a telescope.”

pp 119.

 Denning recalls his own observations of a peculiarly dim lunar eclipse:

On Oct. 4 1884, I noticed that the opacity was much greater than usual; at a middle period of the eclipse the Moon’s diameter was apparently so much reduced that she looked like a dull, faint, nebulous mass, without sharply determinate outlines. The effect was similar to that of a star or planet struggling through dense haze.

pp 119

In contrast, Denning describes the eclipse of March 19, 1848 as unusually bright:

The Moon presented a luminosity quite unusual. The light and dark places on the face of our satellite could be almost as well made out as an ordinary dull moonlight night.

pp 119.

In addition to these records, Mr. Denning mentions some explanations for the variability of the intensity of such eclipses. In particular, he describes a theory first suggested by the great German astronomer and mathematician, Johannes Kepler, who attributed this variability to differences in the humidity of the atmosphere, as well as more contemporaneous explanations proffered by a one Dr Burder, who attributed such changes in the activity of the solar corona.

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Author’s note: Mr. Denning did not mention the considerable effects of atmospheric dust, which has a known reddening effect on astronomical bodies, e.g. sunsets, owing to a phenomenon known as Rayleigh scattering. His description of the unusually dim appearance of the lunar eclipse of October 4 1884, could be explained by the Volcanic eruption of Krakatoa, Indonesia, in August 1883, which would have ejected a considerable mass of dust into the Earth’s upper atmosphere, causing freak meteorological conditions well into 1884.

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Our satellite presents such a wealth of intricate detail through a Newtonian of moderate aperture, that it is scarcely possible to describe the impact with which it assaults the eye on a clear and tranquil night. The images of the Moon at moderate and high power through this author’s 8-inch f/6 Newtonian would have been broadly comparable to what Mr. Denning saw and recorded so diligently, that it is possible, at least to some degree, to ‘re-live’ the visual extravaganzas he remarks upon in the subsequent pages of his chapter on our faithful satellite in space.

While there is little doubt in Denning’s mind that the Moon is, to all intents and purposes, geologically dead, he is of the opinion, like so many other dedicated lunar observers before and after him, that changes can and do occasionally occur on its surface. Pages 120 through 123 recount a number of observations carried out by historical figures concerning this perennially interesting subject, beginning with the views of Sir William Herschel, who conducted extensive lunar observations using his “most excellent” 6.3 inch Newtonian reflector of 7 foot focus. On page 120 he reproduces Herschel’s lunar observations dated to April 1787:

“I perceive three volcanoes in different places of the dark part of the New Moon. Two of them are already nearly extinct, or otherwise in state of going to break out, the third shows an eruption of fire or luminous matter.”

pp 120.

But other observers soon offered less far-fetched explanations of these ‘fiery’ structures, particularly Schröter, who in fact used an identical 7 foot reflector to that employed by Herschel, suggesting they were due to reflected light from the Earth falling upon elevated spots of the Moon  having ” the unusual capacity to return it.

Denning’s contemporary, Wilhelm Tempel, of comet fame, reported what he thought was an impact of some sort on the evening of June 10, 1866, near the locus of the great crater Aristarchus;

“Of course,” he wrote, “I am far from surmising a still active chemical outbreak, as such an outbreak supposes water and an atmosphere, both of which are universally not allowed to exist on the Moon, so that the crater-forming process can only be thought of as dry, chemical, although warm one.”

pp 121.

On the same page, Denning recounts the extraordinary tale of the German astronomer Johann Friedrich Julius Schmidt (1824-1885), who claimed that the 5.5 mile diameter crater Linné had completely disappeared in 1866;

He averred that he had been familiar with the object as a deep crater since 1841 but in October 1866 he had found its place occupied by a whitish cloud. This cloud was always visible but the crater itself appeared to have become filled up, and was certainly invisible under its former aspect.

pp 121.

Denning discusses the observations of other observers, who took Schmidt’s report seriously, but in the end, the lack of confirmation led him to think that it was a trick of light. On page 122, he also relates the case of a one Dr. Klein, who, in contrast to Schmidt, reported the actual appearance of a “deep, dark crater” – about 18 miles to the west-northwest of Hyginus! This time, Denning himself had a look at the region with his 10-inch With-Browning Newtonian, but like many of his contemporaries, described it as a “saucer like depression” rather than the “sharply cut, deep crater” described by Klein

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Authors note: Schmidt’s observations caused international controversy for several decades, drawing the attention of many astronomers of repute. But while Schmidt had established himself as a careful and experienced observer, in the end the case was considered unproven. It is now known that the visibility of this crater is highly dependent on seeing conditions, being all but invisible under poor conditions of seeing.

Throughout the 20th century, a sizeable fraction of lunar observers continued to search for so-called transient lunar phenomena, which basically refer to any sudden changes to the lunar surface and which have a scientific basis in meteorite impacts, lunar out-gassings and the like. The lunar enthusiast is encouraged to keep reporting such lunar anomalies, as and when they occur. But you need to get out and look to see them!

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In the next section, Mr. Denning brings to our attention to the importance of timing when it comes to observing high resolution objects on the lunar surface:

As the Sun’s altitude is constantly varying with reference to lunar objects, they assume different aspects from hour to hour. In a short interval the same formations become very dissimilar.

pp 122.

Furthermore, Denning offers the reader some excellent advice, which, sadly, is not at all stressed by contemporary lunar observers:

The lunar landscape must be studied under the same conditions of illumination and libration, with the same instrument and power, and in a similar state of atmosphere, if results are to be strictly comparable. But it is very rarely that observations can be effected under precisely equal conditions; hence discordances are found amongst the records.

pp 123.

What follows on from this is an excellent summary of the most prominent lunar visual spectacles, together with brief notes on what can be observed with a modest telescope. The importance of note taking is once again stressed, especially the local time to the nearest minute. The text is illustrated by some exquisite drawings of T. Gwyn Elger (and reproduced quite well in this inexpensive reprint!).

On page 135 Denning discusses the occultation of stars by the Moon, which, he reminds us, occur several times each month! Here he mentions something rather curious:

The stars do not always disappear instantaneously. On coming up to the edge of the Moon they have not been suddenly blotted out, but have appeared to hang on the Moon’s limb for several seconds. This must arise from an optical illusion, from the action of a lunar atmosphere, or the stars must be observed through fissures on the Moon’s edges.

pp 135

The reader is encouraged to find out how the discussion develops!

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Author’s note: One gets the strong impression that Denning was an advocate of the volcanic origin of the lunar craters, a theory that was supported well into the 20th century. This is despite the fact that the impact theory of crater formation was alive and well ever since the time of Dr. Robert Hooke (1635-1703), who was among the first to suggest the latter as a plausible, alternate theory (discussed at length in this author’s up-and-coming book, Tales from the Golden Age of Astronomy), based on experimental science.

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Chapter VII  Mercury

Covering Pages 137-144.

In the opening paragraphs of this chapter, Mr. Denning identifies Mercury as the closest planet to the Sun, though he still gives mention to the elusive planet Vulcan, discussed previously in connexion with the Sun.  He then presents the basic astronomical information about Mercury, including its orbital period, eccentricity, elongations, true and apparent diameter, which, he informs us, varies from 4.5” to 12.9” at superior and inferior conjunction, respectively. These data are essentially modern. Denning also mentions the curious fact that the great Polish astronomer Nicolaus Copernicus, never once saw Mercury!

Copernicus, amid the fogs of the vistula, looked for Mercury in vain, and complained in his last hours that he had never seen it!

pp 138.

Following on from this, Denning discloses the number of sightings of the planet he made at this point in his astronomical career:

I have seen Mercury on about sixty-five occasions with the naked eye. In May 1876, I noticed the planet on thirteen different evenings, and between April 22 and May 11, 1890, I succeeded on ten evenings. I believe that anyone who made it a practice to obtain naked-eye views of this object would succeed from about twelve to fifteen times in a year.

pp 139.

He then follows up with details of particular apparitions of Mercury, as preserved in his voluminous notes, when the planet was particularly bright and striking to the eye, such as in February 1868 and in November 1882.

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Author’s note: It is quite probably true that many an amateur astronomer has never observed Mercury, owing to its very low altitude and proximity to the Sun. Denning was a prodigious observer though and the number of sightings he mentions pays testimony to that precocity.

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With characteristically delightful prose, Denning describes the momentous first sighting of the planet in the telescope and the excitement it induces in the observer:

The first view of Mercury forms quite an event in the experiences of many amateurs. The evasive planet is sought for with the same keen enthusiasm as though an important discovery were involved. For a few evenings efforts are in vain, until at length a clearer sky and a closer watch enables the glittering little stranger to be caught amid the vapours of the horizon. The observer is delighted and, proud of his success, he forthwith calls out the members of his family that they, too, may have a glimpse of the fugitive orb never seen by the eye of Copernicus.

pp 139.

After presenting further historical titbits, he then describes the general appearance of the little planet as it appeared through his telescope;

Mercury has a dingy aspect in comparison with the bright white lustre of Venus. On May 12, 1890, when the two planets were visible as evening stars, and separated from each other by a distance of only 2 degrees, I examined them in a 10-inch reflector, power 145. The disk of Venus looked like newly polished silver, while that of Mercury appeared of a dull leaden blue. A similar observation was made by Mr Nasmyth on September 28, 1878. The explanation appears to be that the atmosphere of Mercury is of great rarity, and incapable of reflection in the same high degree as the dense atmosphere of Venus.

pp 140

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Author’s note: While some observers have reported a pinkish tinge to the planet over the years, this is indeed reminiscent of the appearance of the planet seen in various telescopes over a few decades of time by this author. Regarding Mercury’s lack of an appreciable atmosphere, Denning’s conclusion is absolutely sound. Any primordial air it might have had has long been stripped away by the solar wind. What remains now is an extremely nebulous vapour, consisting mostly of the ions of the alkali and alkaline earth metals.

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Continuing on in this chapter, Mr. Denning discusses the ways in which the enthusiast may derive the maximum amount of information from this small and somewhat elusive world. With his simple, undriven mount, he advises the would-be observer to catch the planet just before dawn and to carefully follow it as it rises higher in the sky.  He refrains from making any detailed studies until a few hours after rising however, when the disk takes on a much steadier appearance. During these better moments, he most likens Mecury to the planet Mars in terms of the dark markings and spots it presents to the trained eye. For this he employed a power of about 212 diameters with his 10-inch silver-on-glass reflector.

On page 141-2, Denning reproduces the details of a correspondence he had with the famous Italian astronomer, G.V. Schiaparelli (of Mars fame) in 1882, who, using a fine 8.5 inch Merz achromatic refractor, agreed wholeheartedly with Denning that Mercury most resembles the Red Planet, at least superficially. Two fine drawings of the planet made by the great Bristolian observer himself are presented on page 143.

Denning further discloses details of Schiaparelli’s belief that the length of Mercury’s day is the same as its orbital period, in the same way as our Moon. He does however stress that these details still required corroboration.

The final pages of the chapter discuss transits of the planet as well as an occultation of Mercury by the Moon, dating to April 25, 1838.

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Author’s note: Schiaparelli’s claims about the length of a Mercurial day were not ultimately borne out. The planet in fact takes twice as long to revolve on its axis (176 days) as it does to complete one orbit of the Sun (88 days). However, this was not determined until 1965 using radar techniques.

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Chapter VIII Venus

Covering pages 145-154

Denning begins this chapter by commenting on the illustrious beauty of Venus at dawn or at dusk, and how the ancient believed the morning and evening stars were not one and the same. As harbinger of the day, Venus was known as Lucifer by the ancient Greeks and Hesperus, when the planet appeared as an evening star. When it appeared as an evening object in the autumn of 1887, Denning recalls that many people thought that the Star of Bethlehem had returned after a 19 century hiatus. He explains that at its greatest brilliancy, the planet is reduced to a slender crescent subtending an angular diameter of 65” at inferior conjunction. And when displaying its full disk, it shrinks in both size and luminous glory, presenting a disk scarcely one seventh as large (9.5”). As anyone who has examined Venus with telescopic aid will attest, the planet can be disappointing:

When the telescope is directed to Venus it must be admitted that the result hardly justifies the anticipation. Observers are led to believe, from the beauty of her aspect as viewed with the unaided eye, that instrumental power will greatly enhance the picture and reveal more striking appearances than are displayed on less conspicuous planets. But the hope is illusive……….. There are no dark spots, of bold outline, such as we may plainly discern on Mars, visible on her surface. There is no arrangement of luminous rings, such as encircle Saturn. There are no signs of dark variegated belts, similar to those that gird Jupiter and Saturn; nor is there any system of attendant satellites, such as accompany each of the superior planets.

pp 146-7.

Nonetheless, Denning concedes that Galileo’s observations of the phases of Venus through his primitive telescopes were enough to put the Copernican principle on a firm footing.

As with observing Mercury, he recommends that Venus is best observed during the day. He then launches into a brief survey of historical observations of the planet by celebrated observers of past centuries including J. D. Cassini (1666), Bianchini ( 1726-7), Schröter (1788) and Sir William Herschel (1777-93), and observations made in his own century including, Mädler (1833) and Di Vico (1840-1). Denning recounts in detail some observations conducted by Schröter, who thought that Venus had enormous mountains, the peaks of which would occasionally penetrate the clouds and reveal their presence in the telescope.

Like Mercury, the rotation period of Venus was unknown in Denning’s day and varied enormously from 23 hours, 21 min (Cassini 1666) to 224.7 days (Schiaparelli 1880).

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Author’s note: Schiaparelli was the closest to getting Venus’ rotation period correct. At 224 days it was less than 20 days short of the modern determined value of 243 days. He deduced this time period by assuming that the planet was tidally locked owing to its closer proximity to the Sun than the Earth. We now know that Venus rotates in a retrograde direction, a result of a possible collision with a large embryonic planet early in the history of the Solar System.

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Beginning on page 150 through 151, Denning discusses the nature of the many faint markings made by observers over the years. He notes that many of these reports were made by astronomers using rather small telescopes and how observers endowed with the visual acuity of the Reverend Dawes, failed to detect any markings with the telescopes he employed. He cautions that small telescopes will often create illusory views:

Perhaps it may be advisable here to add a word of caution to observers not to be hastily drawn to believe the spots are visible in very small glasses. Accounts are sometimes published of very dark and definite markings seen with only 2 or 3 inches aperture. Such assertions are usually unreliable. Could the authors of such statements survey the planet through a good 10- or 12-inch telescope, they would see at once they had been deceived. Some years ago I made a number of observations of Venus with 2-, 3- and 41/2 inch refractors and 4- and 10-inch reflectors, and could readily detect with the small instruments what certainly appeared to be spots of a pronounced nature, but on appealing to the 10-inch reflector, in which the view became immensely improved, the spots quite disappeared, and there remained scarcely more than a suspicion of the faint condensations which usually constitute the only visible markings on the surface.

pp 151

Denning gives mention to one of Venus’ most mysterious and enduring phenomena,  referred to today as the Ashen Light; a faint ‘ashy light’ similar to earthshine seen on the Moon, when the planet is near inferior conjunction and its slender crescent is most prominently displayed. He refers to the kind of illumination as a ‘phosphoresence’. He reports that a one Zanger, based in Prague, observed a ‘coppery ring’ completely encircling the planet on a number of occasions.

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Author’s note: The Ashen Light has a very long history associated with it, dating back to the mid-17th century. One of the finest astronomical artists of the post-war era, Richard Baum, of Chester, England, produced some wonderful renderings of the Ashen Light using his beloved old 4.5 Cooke refractor, which he enjoyed for many years. In more recent times however, some unscrupulous swine stole it from him, the whole affair disturbing him so much that he gave up observing altogether. What a shame!

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The remainder of the chapter discusses alleged observations of a satellite of Venus dating from the 17th and 18th centuries. The putative Cytherean moon, unofficially named ‘Neith’, was never positively identified and the consensus among astronomers of the 19th century was that the earlier sightings were nothing more than an ignis fatuus resulting from ghost reflections from eyepieces and the like. Curiously, Denning mentions the transits of Venus which occurred in 1874 and 1882, which he himself observed and even mentions the ‘future’ transit of 2004, which would thrill a new generation of astronomers.

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Author’s note: It is noteworthy that Denning completely avoids speculating on the nature of the Cytherean environment, particularly in light of the wild speculations that were doing the rounds in the late Victorian period. Back in 1870, his compatriot, Richard A. Proctor (1837-88), embracing Darwinian pseudoscience, thought nothing of considering Venus as the abode of life;

It is clear that, merely in the greater proximity of Venus to the sun, there is little to render at least the large portion of her surface uninhabitable by such beings as exist upon our earth. This undoubtedly would render [the sun’s] heat almost unbearable in the equatorial regions of Venus, but in her temperate and subarctic regions a climate which we should find well suited to our requirements might very well exist … I can find no reason … for denying that she may be considered the abode of creatures as far advanced in the scale of creation as any which exist upon the earth.

Many of Denning’s contemporaries thought it a certainty that life exists on other planets. Today, many of us know better though.

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To be Continued in Part II

 

De Fideli

Further Newtonian Adventures with Double Stars.

'Plotina'; the author's ultraportable 130mm f/5 Newtonian reflector.

‘Plotina’; the author’s ultraportable 130mm f/5 Newtonian reflector.

 

 

 

 

 

 

 

 

 

 

In this department of astronomy, the names of Herschel, South, Struve, Dawes, Dembowski, Burnham, and others are honourably associated and it is notable that refracting-telescopes have accomplished nearly the whole of the work. But reflectors are little less capable, though their powers seem to have been rarely employed in this field. Mr. Tarrant has lately secured a large number of accurate measures with a 10-inch reflector by Calver, and if care is taken to secure correct adjustment of the mirrors, there is no reason why this form of instrument should not be nearly as effective as its rival.

W. F. Denning, from Telescopic Work for Starlight Evenings (1891), pp 290-291

Eye seeth afore I measureth.

Introduction: Having spent several years enjoying the views of double stars of varying degrees of difficulty with a variety of classical achromatic and apochromatic refractors of various apertures (60mm-150mm), this author has dedicated the last 15 months investigating the prowess of Newtonian reflectors in regard to their efficacy in splitting double stars. Surprisingly, a 8″ f/6 Newtonian with traditional spider vanes and a 22 per cent central obstruction was found to be noticeably superior to a first rate 5″ f/12 glass, as well as a 180mm f/15 Maksutov Cassegrain, on all targets, including double stars.

These experiences have collectively led to a deep seated scepticism concerning the traditional claims of self appointed ‘authorities’ who have tended to downplay the Newtonian reflector as a worthy double star instrument. But as the quote from Mr. Denning’s book states above, this prejudice is not derived from sustained field experience. Instead, it is cultivated by, at best, tenuous theoretical considerations. And yet theory counts for nothing if contradictions are found by experimentation, and must be revised in light of new evidences brought to the fore by active observers.

In this capacity, this author has spent several months investigating the performance of a very modest 5.1 inch (130mm) f/5 Newtonian reflector on an undriven alt-azimuth mount. The instrument was modified  in two principal ways:

  1. The original secondary mirror was replaced with a slightly smaller flat (blackened around its periphery), giving a central obstruction of 26.9 per cent, significantly lower than Schmidt and many Maksutov Cassegrains of similar aperture.
  2. Both the primary and secondary mirrors were re-coated with ultra-high reflectivity (97 per cent) coatings delivering a light throughput broadly equivalent to a refractor of similar size.

The instrument has a single stalk supporting the secondary mirror which produces greatly reduced diffraction effects compared with more traditional  Newtonians, yet was found to be sufficiently rigid to deliver very sharp and detailed views of the Moon, planets and deep sky objects.

The single stalk, rigidly supporting the secondary of the 130mm f/5 Newtonian.

The single stalk, rigidly supporting the secondary of the 130mm f/5 Newtonian.

 

 

 

 

 

 

 

 

 

 

The optical train can be accurately aligned in minutes by means of fully adjustable screws on both the primary and secondary mirrors and an inexpensive laser collimator.

The collimating screws behind the primary mirror.

The collimating screws behind the primary mirror.

 

 

 

 

 

 

 

 

Preliminary field testing has shown that the telescope provides very fine high power views of stellar targets under fair to good conditions. Even at  powers beyond 50 per inch of aperture, stars remain round, free of astigmatism and perfectly achromatic. Furthermore, the diffraction spikes attributed to Newtonians are much subdued in this instrument owing to its single vane secondary support. The diagram below shows the relative intensity of diffraction spikes manifesting from various secondary mounting configurations and the reader will note the minimal effects of a single support (seen on far left).

Comparison of diffraction spikes for various strut arrangements of a reflecting telescope – the inner circle represents the secondary mirror

Comparison of diffraction spikes for various strut arrangements of a reflecting telescope – the inner circle represents the secondary mirror.

 

 

 

 

 

Materials & Methods: The telescope was mounted on an ergonomic but sturdy Vixen Porta II alt-azimuth mount equipped with slow motion controls on both axes. the instrument was carefully collimated prior to the commencement of observations using a laser collimator. No cooling fans were employed. A red dot finder was used to aim the instrument and various oculars and barlows were used to resolve pairs. For fainter stellar targets, the system was centred first using a 32mm SkyWatcher Plossl which delivers 20x and an expansive 2.5 degree true field.

Results:

Date: 12.05.16

Time: 00:00-00:30 UT

Seeing: Antoniadi II-III

Epsilon Lyrae: x 271; all four components cleanly resolved, stars round, white and undistorted. No diffraction effects noted.

Pi Bootis: Easy at 150x. Components appearing white and blue-white.

Mu Bootis (Alkalurops): Wonderful triple system; fainter pair (magnitudes 7 and 7.6) separated by 2.2″ and perfectly presented at 271x. This pair has an orbital period of just 260 years!

Epsilon Bootis: Primary (magnitude 2.5) presenting in a lovely ochre hue and its fainter companion (magnitude 4.7) easily picked off at 271x.

Delta Cygni:  Magnitudes: 2.89, 6.27, separation:  2.7″

Well split at 271x, although conditions a little turbulent and not yet at an optimal altitude for observation.

Date: 13.05.16

Time: 00:00-00:30 UT

Seeing: II. Indifferent seeing at sunset (III-IV), improving as the night advanced (II).

Temperature: +7.5C

Xi UMa: beautiful clean split of this 1.6″ pair (magnitudes 4.3 and 4.8) at 271x

Epsilon Bootis: textbook perfect split @ 271x

Delta Cygni: Child’s play this evening, separation 2.7″. Companion presented as a perfectly round, steely grey orb @271x.

Beta Lyrae: remarkable multiple star system. Four white/blue white stars framed in the same field at 271x.

O^1 Cygni: a corker at 20x, but more fetching at 81x. Orange and turquoise stars, with the former showing its blue magnitude 7 companion.

Date: 15.05.16

Time: 22:30 UT

Seeing: II-III, clear, brightening moon, twilit

Temperature: +3.5C

Iota Cassiopeiae: Just one entry tonight. More challenging to locate owing to its relatively low altitude above the northern horizon and the encroach of twilight. All thee components well resolved at 271x. This is the third successful split of this attractive multiple star system with the same instrument.

Date: 21.05.16

Time: 22:10 UT

Seeing: II, partially cloudy, twilit.

Temperature: +10C

Epsilon Bootis: Another lovely split this evening @271x. Primary(magnitude +2.5) orange and the secondary a regal blue (magnitude 4.9) separated by 2.8″.

Xi Bootis: Striking yellow and orange components (magnitudes 4.7 and 7, respectively), separated by ~6.5″ and beautifully framed @ 150X.

Rho Herculis: A comely pair of blue-white stars shining at magnitudes +4.5 and +5.4. Easily resolved (4.0″)@271X.

22:30UT

Epsilon 1 & 2 Lyrae: textbook perfect split of all four components @271x. Subtle colour differences noted between the stars.

22:45 UT

Delta Cygni: Perfectly resolved at 271x. Magnitudes: 2.89, 6.27, separation:  2.7″

Date: 22.05.16

Time: 23:10UT

Seeing: II, very good, mostly clear, twilit, bright Moon low in south.

Temperature: +9C

Marfik(Lambda Ophiuchi): Quite hard to track down owing to an unusual amount of glare in the southern sky. System split at 271x. The components ( magnitudes 4.2 & 5.2), well resolved. Tightest system so far resolved with this instrument: 1.4″. Both stars appeared creamy white and orientated roughly northeast to southwest. Superficially, very much like Xi UMa but slightly more challenging.

No’ bad ken.

Date: 24.05.16

Time: 00:10 UT

Seeing: I-II, excellent steady atmosphere, no cloud, twilit, cool.

Temperature: +5C

Pi Aquilae: Another good target affirmatively resolved this evening. Separation 1.5″ with magnitudes of 6.3 and 6.8. Power of 271x applied. First hint of duplicity seen shortly after local midnight when the system was quite low down in the east, but much better presented at 23:45 UT when it rose a little higher.

Delta Cygni: Another textbook perfect split! This system is child’s play with this telescope, but remains a good indicator of local seeing.

I would warmly encourage others using this telescope, or its closed tubed counterpart, to confirm these findings.

Date: 28.05.16

Time: 22:45 UT

Seeing: II, good stable air for double star work, cloudless sky, twilit.

Temperature: +6C

Epsilon 1 & 2 Lyrae: beautiful easy and dazzling split of all four components @271x

Delta Cygni: Another textbook perfect split of this very unequal magnitude pair @271x

Mu Cygni: difficult to find as it is currently lower down in the east under twilit conditions. Excellent multiple star system, A-B well split @271x, colours white and yellow (+4.8/6.2 magnitudes, respectively), separation ~1.66″. Another tight, unequal magnitude pairing. C component too faint to pick off in the twilight. D component (+6.9) seen about 3′ off to the northeast.

Doing well so far don’t you think?

Ps. Interesting findings from a few guys here.

Date: 29.05.16

Time: 23:10 UT

Seeing: II, almost a carbon copy of last night. Twilit.

Temperature: +7C

Just two targets this evening.

Epsilon Bootis: a good ‘warm up’ system. The telescope showed a textbook perfect split during the finest moments at 271X. I have found that wearing a good heat-insulating jacket and hat gives noticeably better results on cooler nights, as thermal energy from the body can sometimes distort the image at least for a wee while.

From there I moved to my target system for the evening.

Sigma 1932 AaB: a very challenging system in Corona Borealis. It is located about 3.67 degrees directly west of Alphecca (alpha CrB) which is easily seen even in twilight. My 32mm SkyWatcher Plossl, which yields a field of view of 2.5 angular degrees was used, together with my star atlas, to finally track down this magnitude 7 system. After a few false starts, I eventually centred the target system, cranked up the power to 271x and, with a concentrated gaze, obtained a good split! This binary system consists of a pair of yellowish stars with equal magnitudes (7.3 and 7.4, respectively) oriented roughly east to west and separated by 1.6″.

Battle o' the weans. In the foreground a 90mm Apo, in the backgroud, a 130mm Newtonian.

Battle o’ the weans. In the foreground a 90mm Apo, in the backgroud, a 130mm Newtonian.

 

 

 

 

 

 

 

 

 

 

Date: 30.05.16

Time: 23:00-23:30 UT

Seeing: A fine and mild night, remaining very good (II), high pressure bubble stabilised over Scotland, some intermittent cloud, twilit. Midge flies back.

Temperature: +11C

Tonight, I wanted to compare and contrast two very different telescopes in respect to their ability to split a few of the tougher pairs visited thus far; a 90mm f/5.5 doublet Apo (retail price now £912 UK) and the 130mm f/5 Newtonian (~£200 UK with the modifications).

System:Delta Cygni

90mm glass; difficult split @208x

130mm speculum: much more cleanly resolved@271x

System: Pi Aquilae*

90mm glass: very dim, touching @208x

130mm speculum: cleanly resolved/brighter @271x

System;Marfik*

90mm glass: dim, elongated @208x

130mm speculum: fully resolved /brighter @271x

*Suboptimal altitude

You cannae change the laws o’ physics captain!

And ignorance of the law is no excuse.

Oh vanity of vanities!

Self-evidently, an unfair comparison: the 130mm f/5 Newtonian is clearly the superior double star instrument.

The words of the prophet, Isaiah, come to mind;

For fools speak folly,
their hearts are bent on evil:
They practice ungodliness
and spread error concerning the Lord;
the hungry they leave empty
and from the thirsty they withhold water.
Scoundrels use wicked methods, they make up evil schemes
to destroy the poor with lies,
even when the plea of the needy is just.
But the noble make noble plans,
and by noble deeds they stand.

Isaiah 32:6-8

Date: 31.05.16

Time: 23:05 UT

Seeing: III; significantly more turbulent than last night. Twilit.

Temperature: +10C

This evening I had intended to concentrate my observations on one target; the very difficult sub-arc second companion to Lambda Cygni, using my best instrument; a 8-inch f/6 Newtonian, in order that I might train my eyes to see this companion (separated by 0.9″) in my smaller 130mm instrument.

Using the 130mm as a seeing gauge; I found Epsilon 1 & 2 Lyrae to be resolved well but nearby Delta Cygni was poorly resolved. This was also found to be the case in the 8-inch aperture.

Project shelved for a better night.

Date: 01.06.16

Time: 23:30 UT

No opportunities afforded this evening owing to the encroach of haar after sunset.

Let us consider some of the optical principles relevant to splitting such a tight pair.

Diffraction theory states that the position of the first bright ring (between 1st and 2nd minima) is located at a linear radius of 1.63 lambda x F where lambda (wavelength) is quoted in microns and F is the focal ratio of the scope. By dividing this quantity by the focal length we obtain the angular radius of the 1st minimum (in radians) and this yields (1.63 x lambda)/D where D is the aperture of the scope in metres.

Now, there are 57.3 angular degrees in a radian and 3600 arc seconds in each angular degree, so if we multiply the above expression by 57.3 x 3600 = 206280 and so we arrive at 206280 x (1.63 x lambda)/D.

Setting D = 0.1m for example, and lambda = 0.55 microns (green)  yields 1849300 micro arc seconds, which is 1.85”.

Or more generally, the locus of the first diffraction ring is 185/D where D is the aperture of the telescope expressed in mm.

Applying this formula to the 200mm and 130 mm reflectors, the position of the first diffraction ring is 0.9” and 1.4”, respectively. Thus, the companion to Lambda Cygni will be located on the first diffraction ring in the 8-inch instrument, and inside the ring in the case of the 130mm telescope.

The primary has a magnitude of +4.5 and the secondary, + 6.3, so there is a magnitude differential of 1.8. The significant brightness differential makes this system more difficult to crack.

The Dawes limit for a 130mm (5.1 inches) ‘scope is given by 4.57/D in inches, which is ~0.9”.

More on this here.

Date: 02.06.16

Time: 23:30 UT

Seeing: III-IV, very turbulent

Conditions clear but remaining very turbulent. A light, northeasterly air flow is likely the culprit(see my local weather; Stirling, Scotland).

My notes show that I have glimpsed the companion to the primary on a few occasions over the last few summers with my 5″ f/12 achromatic. But I have seen it much more clearly – and also on a few occasions – with the 8″ f/6 Newtonian.

Date: 06.06.16

In order to maximise my chances with Lambda Cygni, I have decided to wait until August at the earliest, when the system will be high overhead here, in a dark sky. Patience is a virtue is it not? And I can afford to be patient with this one, as it is a very slow moving binary and so will remain very challenging for a good few years to come. So no hurry.

The capabilities of the 130mm f/5 on double stars have already well exceeded my expectations. My experiences with the smaller, 90mm refractor especially, have reinforced the notion that aperture is a vital commodity when it comes to seeing objects clearly and distinctly. It pays to remember that resolution scales with aperture. That’s why it is easier to see things in the 130mm than the 90mm, irrespective of how fancy its optics and mechanics are. And this can be tested, again and again and again…..ad nauseam.

This is factual knowledge, and facts are stubborn and immutable things!

Physics pays no attention to human hubris.

Physics cares little for hubris.

 

 

 

 

 

 

Over the next few months I would like to return to the many beautiful and easy systems within reach of this remarkable telescope; even in heavy twilight.

Time: 23:00-59 UT

Temperature: +11C

Seeing: II, good, a little hazy, twilit.

I walked through the garden in the cool of the evening, after a very warm and sunny day. I set up the 130mm f/5 as usual and began to explore some of the nicer double stars of the sky.

Mizar & Alcor: A perennial favourite, high overhead this time of year, dazzlingly bright, the light from these stars fills the field and induces instant joy. Well framed at 81x in my trusty Baader mark III zoom.

Cor Caroli (Alpha CVn): Easy to find under the handle of the Ploughshare. Both components appearing white to the eye with magnitudes 2.9 & 5.6.

Alpha Herculis (Rasalgethi): A corker! At 108x, this pair presents as marmalade orange and blue-green, which orbit their common centre of gravity every 3600 years.

Albireo (Beta Cygni):  A stunning sight in the little reflector at 81x. Glorious contrast of colour; orange (magnitude 3.1) primary, blue-green secondary (5.1).

61 Cygni: historically very significant as the first star system to have its distance measured in 1838 by F.W.Bessel. Only 10.4 light years away. Both stars are cool, orange dwarfs with magnitudes 5.2 and 6.1.

Eta Cassiopeiae: A bit more challenging to locate in the strongest twilight coming from low in the northeast. Easily split at 81x, presenting as orange and red (magnitudes 3.5 & 7.5, respectively). These constitute a true binary system, with a period of about 480 years.

A quick peek at a more difficult pair:

Pi Aquilae: Once again, beautiful and easy to resolve in the 5.1” reflector at 243x. I have been observing this system for five years now, with various instruments. My notes from the end of July 2011 showed that it was very difficult with a high-quality 4” f/15 classical refractor, the twilight making it challenging. Observations made with variety of 5” refractors over the same period – and also in summer twilight –  show that it is not difficult in these sized instruments (only anomaly recorded in an optically so-so 6” f/8 speculum used for outreach also from 2011, where it was relatively poorly seen).  In the absence of a good 4” refractor at present, this provides good evidence that the 130mm reflector is indeed operating closer to the performance of a 5” glass than a 4” glass, which is very encouraging.

Before leaving the field, I spotted Saturn below the tree line in the south, so I decided to uplift the telescope on its Porta II mount and walk about a hundred yards to a grassy spot at the local primary school grounds, where I could better aim the telescope. Despite its very low altitude, it was a beautiful sight at ~150x, it glorious ring system now wide open for business. Cassini Division seen, as well as some banding on the Saturnian globe.

Vicious midge flies making any further observations uncomfortable, the vigil was aborted shortly before 1 AM local time.

Date: 08.06.16

Time: 23:00-30 UT

Seeing: II, good and stable, variable amounts of thin cloud, twilit.

Temperature: +10C

Polaris: Always a lovely system to study, even in the twilight. In the telescope at 108x, the 2nd magnitude primary (Polaris A) presents as a beautiful creamy white, the secondary a haunting bluish grey some 6 magnitudes fainter seen in the 10 o’ clock position in the 130mm Newtonian. A third companion lies much closer to Polaris A but is woefully beyond the powers of any backyard telescope to resolve. Interestingly, all three stars in this system, located about 430 light years away, are of the F spectral class, and thus should present with the same colours. This is readily seen with Polaris A but the exceeding faintness of the Polaris B hides its true colour. Polaris B orbits A at a distance of about 2400 further out than the Earth-Sun distance, taking over 400 centuries to complete a single lap.  Polaris A is a giant, pulsating star, part of a class known as Cepheids. With such stars, humans have been able to extend the plumbline of their reach into the realm of the galaxies. Stars like Polaris A have helped us gain a truer sense of the vastness of the Universe in which we miraculously inhabit. These are some of the things I like to ponder on, whilst spying the Pole Star.

16 Cygni: A fourth magnitude system a little to the northeast of the lovely red variable star R Cygni. In the 130mm f/5 at 81x, the decent light gathering power of the instrument presents the pair  in their natural colours: a yellow primary (magnitude 4) and golden secondary (magnitude 6), separated by about 40 arc seconds of sky.

Eta Lyrae: Located a few telescopic fields east of Vega, this is normally a very easy system to crack at low powers (~40x) with a magnitude 4.4 blue-white primary and 9th magnitude secondary wide away. In the twilight, I find a higher power of 108x is needed to see the faint secondary well, and is even better presented again at 150x. Much more gloriously presented from a truly dark sky.

Date: 17.06.16

Time: 22:30-59 UT

Temperature: +7.5C

Seeing: II-III, clear, twilit, bright waxing gibbous Moon culminating in the south. Evening made especially pleasant by the absence of midge flies, which don’t like temperatures below 10C.

After over a week long hiatus in the weather, which brought endless cloud and some rain, the sky finally cleared up this evening, allowing me to resume my adventures with my 130mm f/5 Newtonian.

Two reasonably challenging doubles to start with:

Epsilon Bootis: beautifully sharp and well resolved at 195x

Delta Cygni: Ditto @195x; always a joy to observe this system so well.

Iota Bootis: A wonderful low power system, located about 4 degrees northeast of Alkaid (at the tip of the handle of the Ploughshare). At 81x, the system was beautifully framed  and showed a yellowish primary(magnitude +4.8) well separated from a bluish secondary,  some three magnitudes fainter (+7.5). Very fetching colour contrast in the Newtonian!

95 Herculis: Found by panning some 10 degrees east of Delta Herculis. To my eyes, this nearly equal magnitude pairing(4.9/5.2) has a very subtle colour contrast: one appears silvery, the other creamy white. Easily resolved at 81x. Consulting my old Burnham’s Celestial Handbook Vol 2, there is an interesting discussion on the historical colour presentation of this pair, especially from some eccentric 19th century observers!

What colours do you see?

How wonderful it is to get outside on this beautiful mid-summer evening!

Date: 18.06.16

Time: 22:30 UT

Temperature: +10C

Seeing: II, some hazy cloud, bright Moon in south.

Epsilon 1 & 2 Lyrae: Textbook perfect split of all four components at 243x

Delta 1 & 2 Lyrae:  Easily found in the low power (20x) field of my 32mm SkyWatcher Plossl, just a few degrees to the east of Vega. No need for higher power with this system; lovely colour contrast – red and blue-white. Stars physically unrelated i.e an optical double.

SHJ 282: Seen in the same lower power field of Beta Lyrae, some 1 degree to its northeast. Under darker skies, it forms a wonderful sight in the 2.5 degree field of the 32mm Plossl, together with the celebrated Ring Nebula (M57). At 41x, this comely system (actually triple) looks like a copy of Albireo; an aureal primary well separated from its pale blue secondary.

Date: 27.06.16

Time: 22:45-23:10UT

Temperature: +10C

Seeing: II, very good, partially clear, beautiful noctilucent clouds in the northeast, fresh westerly breeze, nae midgees.

The weather has been quite unsettled of late, with little in the way of clear skies, but this evening I grabbed an opportunity with both hands and fielded my bonnie 130mm Newtonian.

A number of systems visited this evening including:

Delta Cygni: wonderful split and (as usual) easily resolved at 243x. Lovely round stars well separated in the twilight.

Epsilon 1 & 2 Lyrae: Textbook perfect at 243x

Epsilon Bootis: Very easy for this telescope, as I have found on many occasions now. Lovely colour contrast at 243x

Pi Aquilae: Better positioned these days. Easily split at 243x

11 Aquilae: Found by centering Zeta Aquilae in the low power (20x) field. 6th magnitude 11 Aq lies just one degree or so to its west. At powers up to 100x or so, only the white 6th magnitude primary is visible, but when the power is cranked up beyond about 150x, the much fainter 9th magnitude companion was observed wide away. Reasonable concentration is required to tease this out of the twilight. Once picked off, the greyish companion was better seen at higher powers (243x). This system is far more glorious in a fully dark sky, and I shall look forward to visiting it again in August.

All in all, a grand half hour under a Scottish summer sky. My little Newtonian reflector is most assuredly a proficient double star telescope. The unbridled joy of discovery!

Date: 29.06.16

Time: 22:45-23:20 UT

Seeing: Excellent, I-II, gentle breeze, very little cloud, twilit.

Temperature: +8.5C

After assessing the seeing in the 130mm Newtonian and judging it fine ( as evidenced by cleanly splitting Delta Cygni at 243x), I fielded my 8-inch f/6 Newtonian and turned it on Lambda Cygni, now considerably higher in the sky and applied a power of 450x. I also employed a Baader single polarising filter, which helped to reduce glare and darken the sky. I could indeed see the companion to the primary star intermittently and oriented north to south. And during the better moments I could see that it was clearly disembodied from the primary. I then turned the 130mm on the same system, employing a power of 365x with the polarising filter. Letting the image settle down as it moved across the field, I observed good elongation in the same orientation, but no separation.

This was a most exciting and encouraging vigil, the first of many more I hope.

Date: 01.07.16

Time:22:50-23:40 UT

Temperature: +7C

Seeing: II, good clear spells, some cloud, westerly gusts, cold, twilit.

After a day of heavy and frequent rain showers, I enjoyed a short clear spell around midnight.

Iota Cassiopeiae: Fairly tricky to track down in twilight, but was rewarded with a lovely clean split of this picturesque triple star system at 243x.

Eta Cassiopeiae: Picturesque colour contrast pair (A/B orange and yellow). Easy to split at powers at ~100x.

Sigma Cassiopeiaie: located a few degrees southwest of the easternmost star in the constellation ( Beta), this is a wonderful target for small telescopes. It consists of two blue-white stars separated by about 3.2″. The primary shines with magnitude 5.0 and the secondary, 7.2. Best seen at magnifications > 150x.

Delta Cephei: Beautiful and easy with the 130mm Newtonian. The stars appeared pure white and easily resolved even at low power but nicely framed at 81x. The primary is actually another Cepheid variable (described above in relation to Polaris).

Two tighter test systems visited:

Delta Cygni: good clean split at 243x

Epsilon Bootis: ditto at 243x

Date: 05.07.16

Time: 23:05-30UT

Seeing: III-IV, below average seeing, partially cloudy.

Temperature: +8C

Fairly choppy seeing this evening, as evidenced by somewhat bloated stellar seeing disks observed with the 130mm f/5 Newtonian.

Delta Cygni: barely resolved at 243x

Epsilon Bootis: split but not cleanly at 180x

Xi Bootis: yellow and orange pairing, easily resolved (6.4″) at 150x

Pi Bootis: Blue and yellow components, easily resolved (5.6″) at 150x

Zeta Coronae Borealis: Lovely yellow and blue-green components easily resolved (6″) at 150x

Mu Bootis (Alkalurops): All three components resolved easily with the 130mm Newtonian at 243x. System previously visited on May 12 last. The two seventh magnitude stars (B/C) were surprisingly well split (~2″), a consequence I suppose of their low brightness which curtails the size of their seeing disks. Fainter pairs seem less susceptible to seeing conditions.

Date: 08.07.16

Time: 22:40-23:00 UT

Temperature: +12C

Seeing: III-IV, remaining turbulent, mostly cloudy.

Further trials with the 130mm f/5 Newtonian.

Delta Cygni : unresolved at 183x

Epsilon 1&2 Lyrae: resolved at 183x

Cor Caroli: very pretty at 63x

Date: 11.07.16

Time: 22:45- 23:00 UT

Temperature: +13C

Seeing: III-IV, very turbulent mostly cloudy, a few suckerholes appearing here and there.

Two instruments fielded this evening; a 130mm f/5 Newtonian and a 90mm f/5.5 apochromatic refractor (price now hiked up to £1017?! i.e. fourth successive hike since review)

Epsilon Bootis (Izar): Companion resolved reasonably well with 130mm  reflector but very poorly (if at all) with 90mm refractor at comparable magnifications i.e.~180x. Quite revealing really!

Mission aborted owing to light drizzle.

Date: 12.07.16

Time: 22:30-23:00 UT

Seeing: III, partially clear, cool, twilit.

Temperature: +10C

The conditions were slightly improved over last night. I fielded the 130mm f/5  Newtonian again and examined the following systems. I employed a single polarising filter which does a very good job removing some glare and improving the aesthetic of the stellar images, especially in twilight.

Epsilon 1&2 Lyrae: easily split at 181x.

Epsilon Bootis: well split at 180x

Delta Cygni: good split at 180x and 243x

Low down in the east, I visited Delphinus for the first time this season.

Gamma Delphini: A corker at 181x! Located some 100 light years from the Solar System, the primary(magnitude +4.4) shines with a lovely marmalade orange hue, while the secondary (magnitude 5.0) shows up as lime-like. 9 arc seconds separates them.

Struve 2725: Seen in the same high power field as Gamma Delphini, this fainter system can be seen a little to the southwest of Gamma. This pair is a bit more challenging to spot, the primary and secondary having magnitudes of 7.5 and 8.4 respectively and orientated north to south. To my eye they both look white and are separated by 6″.

No’ bad innings for an average July evening, ken.

Date: 13.07.16

Time: 22:30-23:00 UT

Seeing: II-III, an improving picture, though not where I would like it to be. Partially cloudy, twilit.

Temperature: +10C

Systems visited this evening with the 130mm f/5 Newtonian (with single polarising filter) included:

Delta Cygni: well split at 181x

Iota Cassiopeiae: A beautiful, delicate triple system, well resolved at 181x but more compelling to behold at 243x

After spending about five minutes admiring the comely, sanguine Garnet Star (Mu Cephei), I move the instrument a little to its southwest until I arrived at a field of view containing two other stellar systems of interest:

Struve 2816: A magnificent triple system (actually quadruple). All three stars are arranged in a line running roughly northwest to southeast. A/B looks yellow to the eye (magnitude +5.6) with two equally bright stars (C and D), located 12″ and ~20″ away from the primary, respectively. A grand sight at 181x.

Struve: 2819: Just off to the northwest of Struve 2816, this is a fainter system requiring high powers to see well. Both stars appear white to the eye. The primary is magnitude + 7.4 and has a fainter companion (magnitude +8.5) ~13″ off to its northeast. Best seen at 243x.

Very much looking forward to darker and more stable skies coming back in a few more weeks.

Date: 18.07.16

Time: 22:20-30 UT

Seeing: sultry, clouded out, midge flies by the legion, twilit.

Temperature: +18C

Poodle versus Plotina

Lens versus Speculum.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I was hoping to get some observing done this evening, as the forecast looked reasonably promising after a long spell of very unseasonal weather (The Open at Troon sure wasn’t pretty lol). I have not been able to make any additional progress beyond what I’ve recorded but having been at this a few months now and having seen what I’ve seen, my conclusions are as follows;

The modified 130mm f/5 appears to be an excellent double star instrument! This came as a quite a surprise to me, as I was not entirely prepared for what it could deliver given its very modest cost. All of this can be tested, of course, and I’d warmly encourage you to have a go.

The instrument will comfortably outperform any 90-100mm refractor given a fair trial (proper acclimation, optical train alignment, reasonable to good seeing conditions, etc.). It is especially adept at resolving close, fainter pairs of roughly equal brightness.

Millimetre for millimetre, its performance in comparison to a refractor of equal aperture is much closer than is commonly reported (or commonly believed), though I would concede that the refractor will have an edge when pushed to the limits*.

*Valid only over the aperture ranges studied.

My conclusions are fully in agreement with the comments made by W.F. Denning (1891), reproduced above.

I will continue to monitor these and other double stars, God willing, in the coming months and years and will report back in due course.

It has been an absolute pleasure discovering the many charms of this little Newtonian. As telescopes go, there is something very endearing about their ingenious simplicity, and given half a chance, they can show you remarkable things.

As I write this, there are more encouraging signs that the prejudice traditionally attributed to Newtonians for this kind of work is being lifted and that is great to see! Just have a look at the CN Double Star forum to see some examples. I believe much of this prejudice is/has been due to the usual suspects: laziness, lack of interest, somewhat irrational, material attachment to other kinds of telescopes, and the like. You see, you don’t need a big vainglorious refractor (I should know, I’ve got one lol) to do this kind of work, and dare I say, one can actually derive a greater level of satisfaction achieving goals with these modest instruments over more traditional ones. You begin to see the hobby in a whole new light.

Thank you for following this blog.

Clear Skies!

Neil.

Updates

Date: August 17, 2016

Time: 00:05h BST

Seeing: Excellent: I, excellent definition, fairly bright sky owing to very late gibbous Moon low in the south, gentle westerly breeze.

Temperature: +12C

Instruments: 203mm f/6 & 130mm f/5 Newtonians, Baader single polariser.

Observation: The 8-inch reflector easily resolved Lambda Cygni B (0.9″), clearly seen at 450x and orientated at right angles to the direction of drift (E-W). Both components presenting as perfectly round and clean white. Deeply impressive!

The 130mm f/5 showed the system as plainly and strongly elongated N-S, power employed x325. Careful attention to accurate collimation necessary. Best evidence for the appearance of duplicity thus far recorded with this instrument.

Date: August 28 2016

Time: 23:10 BST

Seeing: Excellent (I), a bonnie evening, very steady, no clouds, no Moon, cool.

Temperature: +10C

Instruments: 203mm f/6 and 130mm f/5 Newtonian reflectors, Baader single polariser.

After obtaining an excellent high power split of delta Cygni & pi Aquilae with both instruments, I turned the telescopes toward lambda Cygni. The 8-inch served up another clear split of the 0.9″ B component at 450 diameters, just like the evening of August 17. The 130mm, once again showed strong elongation (north to south orientation) at 325x and 406x, but was not split.

 

De Fideli.

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.
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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

A Short Commentary on R.G Aitken’s “The Binary Stars.”

The Great Lick Refractor.

The Great Lick Refractor.

 

 

 

 

 

 

 

 

 

 

R.G. Aitken faciebat, Anno Domini 1918

 

Some biographical notes on the author:
Robert Grant Aitken (1836-1951) was born in Jackson, a small mining town in California, in the years after the gold rush. He developed a serious middle ear infection as a child, which led to his partial deafness and the use of a hearing aid for the rest of his life. The illness meant that he was unable to begin his schooling until age nine. Nonetheless his considerable academic abilities ensured that he received a reasonable school education, after which time he embarked on a journey across the American continent, where he initially had planned to study for the ministry at Williams College, Massachusetts. There his career took a new twist when he was introduced to the influential astronomer, Professor Truman H. Safford (1806-1901), who encouraged him to also study for a BA in mathematics.

After graduating, Aitken took an academic post at the University of the Pacific (San Jose) where he taught mathematics and theology to prospective undergraduates. After many years dedicated to his teaching post, Aitken began to look for another career allied to research astronomy and by 1894 soon found himself corresponding with Edward S Holden, the first Director of Research at the newly dedicated Lick Observatory atop Mount Hamiliton.

Holden agreed to take him on and in 1895, Aitken and his family took the horse drawn stage coach up Mount Hamilton. There he would begin a trial period of work as a ‘summer student’ but only after two weeks in the job was offered a longer, one year appointment. Aitken actually stayed there for a further 40 years, acting as the Observatory’s Director between 1930 to 1935.

Aitken married miss Jessie Thomas, who bore him four children, eight grandchildren and nine great-grandchildren. Shortly after enduring a nasty fall, Professor Aitken fell ill and died on October 29 1951, aged 87 years.

                                              The book and its contents

From the beginning, Aitken was set to work using the 12- and 36 inch Clark refractors to measure binary stars. At first he concentrated on confirming measures made by Burnham but soon Aitken was making discoveries of his own. Together with his colleague William J. Hussey (1862-1926), they added a 1000 new pairs to Burnham’s magnum opus; The General Catalog of Double Stars. Over his entire career, Aitken discovered 3,087 new double stars and performed measurements of 26,560 pairs!

Aitken at the telescope.

Aitken at the telescope.

 

 

Aitken’s book begins by summarising the work of his predecessors – from Ricioli in the seventeenth century to the monumental work of his illustrious colleagues – S.W Burnham et al. Indeed, the author dedicates the book to Burnham.

By this time, double star astrometry was being conducted with great diligence across the United States, in Britain and on the continent of Europe. The majority of this work was done with classical refractors of long focal length.

Magnifications employed at the 36 inch: Aitken doesn’t mention the particular types but it is assumed that either Huygenian or the achromatic Kelner models were employed. Though not used widely today, they work superbly well with instruments of f/12 relative aperture or slower. Their minimalistic design would have generated images of high contrast and good definition. The lowest working power employed with the 36 inch was 502 diameters for pairs wider than 2 arc seconds. For one arc second pairs, twice that power was found to be ideal. And for pairs of 0.5 arc seconds or less, Aitken used magnifications up to 3000 (83x per inch of aperture) to good effect.
In general, Aitken advocated the maxim; use the highest power that the seeing will permit. On lesser nights, when the air was unsteady, lower than average powers were employed.

Stopping down, diaphragms and all that:
Aitken has formed the definite opinion that stopping down the aperture is more often than not, a hindrance and not a help to the study of double stars. Stopping down was commonly used by observers such as Percival Lowell et al in the erroneous view that finer details could be made out. But while Aitken points out that some of the Lick astronomers – including Barnard and Burnham – occasionally practiced such an activity in the worst conditions, full aperture was almost invariably preferred.

Use of filters

Aitken states that coloured filters can help reduce the glare round a bright primary star making faint companions easier to pick off.

Measurements and Telescope Aperture
On page 55 Aitken reminds us that, “It is hardly necessary to add that an hour in the dome on a good night is more valuable than half a dozen hours at the desk in daylight. Everything should therefore be done to prevent loss of observing time.”

On page 63, Aitken reveals that he and other observers of double stars tended to over-estimate the separation of close pairs especially when a smaller aperture telescope was used. Comparing the micrometer measures of a statistically significant number of stars conducted with a 12-inch refractor and the great 36 inch Lick telescope reveals this trend clearly.
No of stars               Separation in the 12-inch ( “)             Separation in the 36 inch(“)
20                                                0.52                                                            0.42
25                                                0.62                                                            0.54
24                                                1.07                                                            1.03
21                                                1.38                                                            1.39

Aitken notes that this discrepancy is seen in pairs, the separations of which are less than twice the resolving power of the instruments but become negligible in wider pairs. This result was also noted over half a century earlier by the Reverend William Rutter Dawes, which he attributed to the difficulty of superimposing the micrometer wires on the swollen sizes of the Airy disks.

G.P. Bond managed to photograph and measure the wide pair Zeta Ursae Majoris (then 14.2” apart) as early as 1857 while others working with the classical refractor in other observatories had reported getting photographs of separated pairs down to an impressive 1.0″. That said, Aitken admits that such techniques have limited application over the eye in the case of sub arc second pairs – a fact that remained true until recently.

During Aitken’s day, enough data had been amassed by double star observers using various instruments of greater and lesser glory to begin to answer a fundamental question that still eludes binary star astronomers today. Can a formula be found that links the telescope’s resolving power to its aperture? For over half a century, the Dawes Limit was widely touted as the best general formula available. Specifically, it relates to a pair of sixth magnitude stars of equal brightness, and is given as 4.56″/D, where D is expressed in inches. It is noteworthy that Dawes had established this formula mainly from significantly smaller aperture instruments than those which were consummately familiar to Aitken.

In 1914, T. Lewis published a study of double star measures made by a variety of observers employing telescopes with apertures ranging from 4 to 36 inches. His results showed large variations from observer to observer but seemed to gravitate around a maximum resolution given by 4.8″/D for bright equal pairs (> magnitude 8) and 8.5″/D for faint (< 8th magnitude) equal pairs.

Upon analysis of data accumulated by Burnham, Hussey and Aitken using the 36 inch Lick refractor (see page 56), he offers the following formulae:

For bright equal pairs:  4.3″/D (mean magnitudes 6.9 to 7.1)

For equal faint pairs:  6.1″/D ( mean magnitudes 8.8-9.0).

All the Lick astronomers were able to resolve at least five systems that were as low as 0.11″ and one system -the ‘minimum for each observer’ as Aitken himself put it – as low as 0.09″. Aitken goes on to stress that they had found many equally bright pairs that were actually discovered with the 12 inch refractor and shortly thereafter measured by the larger 36 inch to have separations only 0.25″-0.2″ apart!

The resolution results with the large Clark refractors are remarkable and may well represent the limits to which a telescope can resolve given our comfortable existence at the bottom of a shallow sea of air. As a curious aside, in considering what the optimum aperture might be for visual observing, a result was obtained which puts apertures of the order of 0.75 metres (~30 inches) as near the maximum that might achieve these resolution feats.

A note on secondary spectrum and its connexion to resolution

Whatever the benefits a colour free image might be have to viewing extended objects,  it is clear from the data provided by Aitken et al with the 36-inch Lick Refractor that they were able to reach the traditional resolution limit in regard to separating double stars. This provides an interesting historical backdrop to understanding to what extent (if any) secondary spectrum (chromatic aberration) had on the efficacy of any instrument. According to contemporary received wisdom, a single number – the Chromatic Aberration (CA) index arrived at by diving the relative aperture (f ratio) of the instrument by its diameter in inches – is a ‘useful’ parameter in predicting optical performance. Here is a table showing the various CA indices for telescopes of varying f ratio and aperture.

The CA index table showing the putative efficacy of achromats of various relative aperture.

The CA index table showing the putative efficacy of achromats of various relative aperture.

The reader will note that instruments displaying a CA index less than unity are considered to have ‘unacceptable’ levels of secondary spectrum. Yet, this presents a real dilemma; the CA index for the Lick refractor (with a presumed focal length of 694 inches) is a mere 0.52, yet it was clearly able to resolve to the theoretical limit constrained by its aperture. The majority of large classical refractors from the same genre (such as the 26 inch Clark refractor at the US Naval Observatory) would fair similarly in such an analysis although  ironically they performed equally well to the 36 inch Lick.

An instructive way forward is to consider a completely different type of achromat, in particular, a 8″ f/6 rich field refractor recently put through its paces in the field for a  magazine review. This telescope has a CA index of 0.75 and thus should perform better, within the remit of its aperture, than the 36 inch Lick refractor. But this author has discovered that an 8″ f/6 achromatic is an exceedingly poor double star splitter and will not resolve pairs to its resolving limit based on its aperture alone. Specifically, in field tests, the same 8″ f/6 was unable to resolve the triple star Iota Cassiopeiae when a 80mm f/5 achromat could (as an aside, for those who have no experience with an ultra-fast 8″ lens, consider for a minute using a 4″ f/3 object glass to resolve tricky doubles)!

The explanation, in the opinion of this author, lies in the severe spherochromatism – the change in the degree of spherical aberration as a function of wavelength – inherent in even a very well executed 8″ f/6 achromatic doublet. The long focus classical refractors of old, while undoubtedly throwing up proverbial ‘gobs’ of secondary spectrum around bright objects, would have had much reduced spherochromatism at peak visual wavelengths (510-550nm) which would have allowed them to resolve pairs at or near the limit for their aperture.

In short, the CA index, as illustrated above, is simply not credible when applied to double star astrometry. The late professional double star observer, Paul Couteau, who had accrued many years of first hand experience measuring binary pairs with the large refractors at Meudon and Nice in France, suggested that much of the secondary spectrum would have been “lost in the depth of focus of these instruments”. In this capacity, an 8″ f/12 refractor (CA index 1.5) would be vastly superior to a 8″ f/6 when applied to resolving double stars. An instructive example in this regard is to to consider the superlative work by Bob Argyle, based at the Institute of Astronomy at Cambridge University, who has used the 8″ f/14 Thorowgood refractor (1864 Cooke vintage) for many years to measure pairs down to its resolving limit. Thus, caution must be exercised in ‘predicting’ optical performance based on a single figure involving f ratio and aperture. In addition, the work with these large classical achromats clearly demonstrates that better colour correction has no significant effect on resolving double stars; a fact that professional double star astronomers have clearly heeded over the decades. That conclusion also agrees with this author’s extensive experience with these instruments in the field.

The resolution of pairs as low as 0.09″ is remarkable! How can we make sense of this? One has to remember that angular resolution is wavelength dependent and, as such, could create significant inter-individual differences in acuity.

Another possibility is that the Dawes formula is in some ways too restrictive, as it pertains to equal, 6 magnitude pairs. Fainter, tight pairs, with correspondingly smaller seeing discs (and less glare) might be expected to be better resolved. The author notes that the formula 4.3″/D was established from systems at least one stellar magnitude fainter than Dawes.

Resolving power is wavelength dependent as this superlative sequence of images made by Damian Peach show.

Resolving power is wavelength dependent, as this superlative sequence of images made by Damian Peach show.

 

 

 

 

 

 

 

 

 

Chapter IV of the book delves into the mathematical analysis of the ellipse ( which need not concern us further here) and how this can be applied to establishing the true orbit of a binary star system, using the data reduction techniques available to the author in his day. Several methods of analysis are discussed, including that of Kowalsky and its modification by Glasenapp, and Zwier’s method. These techniques are then applied to a number of binary systems to illustrate how raw data can be used to establish the orbital elements. The chapter ends by taking a look at the interesting phenomenon of deducing the existence of very close, invisible companions my observing measurable perturbations in the proper motion of the star as it moves in its Galactic orbit. After discussing the first such case –  Sirius B by Friedrich W. Bessel in 1845 – Aitken briefly discusses some other  examples ‘suspected’ of having analogous companions – Beta Orionis, Zeta Cancri and 70 Ophiuchi – to name but a few.

Chapter V is written by one of Aitken’s colleagues – Dr. J.H. Moore – who discusses the phenomenon of radial velocities of stars. The history of this subject began with the development in the 19th century of the theory of wave mechanics and the exploration of phenomena associated with the Doppler effect. Imagine you are watching an ambulance approach you at speed with its siren blasting. As the sound waves are moving with their own velocity, the waves are compressed in the direction of motion, causing their frequency (pitch) to increase. Conversely, as the ambulance recedes from you, the waves are stretched out and their pitch accordingly decreases. This effect was so named after the Austrian scientist, Christian Doppler (1803-1853), who offered the first known physical explanation for the phenomenon in 1842. The hypothesis was tested and confirmed for sound waves by the Dutch scientist Christophorus Buys Ballot in 1845. Doppler correctly predicted that the phenomenon should apply to all waves, and in particular suggested that the varying colors of stars could be attributed to their motion with respect to the Earth. Specifically, pitch is to sound as colour is to light. Before this was verified, however, it was found that stellar colors were primarily due to a star’s temperature, not motion. Only later was Doppler vindicated by verified redshift observations.

The first Doppler redshift was described by French physicist Hippolyte Fizeau in 1848, who pointed to the shift in spectral lines seen in stars as being due to the Doppler effect. If the star is moving away from us, then the spectrum of Fraunhofer lines would be shifted to lower frequencies, that is, ‘redshifted’. Conversely, if the star is moving towards a stationary observer, those same spectral lines shift to higher frequencies, that is, ‘blueshifted.’

The physical quantity called red shift (z) is provided by the simple formula:
z = (Lambda (observed) – Lambda(rest))/ Lambda (rest)

Furthermore, for stars or galaxies moving at speeds much less than the speed of light, the
velocity of the star (v) can be calculated using the formula:
v = zc
where c is the speed of light in a vacuum (300 million metres per second).

Positive values of z indicate relative motion away from the observer, whilst negative z values indicate relative motion towards the observer.

The effect is sometimes called the “Doppler–Fizeau effect”. In 1868, British astronomer William Huggins was the first to determine the velocity of a star moving away from the Earth by this method. In 1871, optical redshift was confirmed when the phenomenon was observed in Fraunhofer lines using solar rotation, about 0.1 Å in the red. In 1887, Vogel and Scheiner discovered the annual Doppler effect, the yearly change in the Doppler shift of stars located near the ecliptic due to the orbital velocity of the Earth. In 1901, Aristarkh Belopolsky verified optical redshift in the laboratory using a system of rotating mirrors.

It is noteworthy that Dr. Moore still entertains the possible existence of the lumeniferous aether – a hypothetical medium through which light waves were believed to propagate. An aether of kinds seemed like a reasonable proposition at that time since all known longitudinal waves required a medium in order to propagate through space. Moore doesn’t offer a firm opinion one way or the other on this matter, but is silent on the results of a series of experiments conducted by Michelson and Morley in the 1880s and by Michelson and Miller between 1902 and 1904, all of which produced a null result for the aether.

Although all modern spectra are obtained using high resolution diffraction gratings, Moore explains that the spectrographs recorded with the large refractors employed the simpler, prismatic technique.Chapter V and VI cover quite a lot of technical detail discussing the orbits of binary stars and their geometries.  At the time of writing (1918), the orbits of 112 visual and 137 spectroscopic binaries had been determined.

In order to obtain spectra, the large refractors had to be carefully fitted with spectrometers which could accurately record the radial velocities of the components in a binary system – whether it be a visual or spectroscopic. Plate IV shows the Mill’s spectrometer attached to the 36 inch Lick refractor. The spectra were recorded photographically and this required for long, guided exposures often lasting 60 to 90 minutes  for moderately bright stars ( magnitude 5) and longer for fainter pairs. In addition, the telescope had to modified to focus the rays on the photographic plates. This required placing corrective optics (of 2.5 inches aperture) between the object glass and spectrograph, which further reduced the light gathering capability of the telescope. The reason for this is due principally to the lack of anti-reflection coatings on the glass elements and increased absorption of light by the corrective optics.

Dr Moore explains in Chapter VI that the long focus refractors were particularly well suited to the task of taking these spectra owing to their ability to naturally produce large enough image scales to measure the positions of those lines in relation to those obtained from a known laboratory source. Dr Moore explains that to accomplish this, the light from a suitable source (such as an iron arc) is made to pass over the same light path that the star takes. This acted as a so-called comparison spectrum, by which the redshifts were measured. The spectrograph had to be temperature controlled to obtain the highest quality spectra and so the Mill’s spectrometer was enclosed in a special wooden box that was lined with felt. A string of resistors were arranged along the length of the felt and were activated by a very sensitive mercury-in-glass thermostat, which kept temperatures constant to a few hundredths of a degree C throughout the night.

On page 120, Moore concedes, from practical experience, with the 36 inch refractor and the 37.5 inch silver on glass reflector in Chile, that the former is less temperature sensitive  and naturally better suited to obtaining high resolution spectra. Moore concedes that for high dispersion work (such as at H alpha wavelengths), the refractor is better suited than the reflector. For low dispersion work, the reflector is to be preferred. Since the introduction of aluminium coatings (with their near constant and high reflectance across the visible spectrum)  in 1932 however, reflectors have greatly exceeded the results of the giant refractors of yesteryear.

Although the earlier spectral classification scheme of Cardinal Secchi is mentioned in passing, Aitken adopts the Harvard Classification Scheme throughout the book, the same  basic scheme used by contemporary astronomers.

Chapter VII deals with the fascinating topic of eclipsing binary stars. Aitken mentions that Professor E.C Pickering made a detailed analysis of Algol’s light curve as early as 1880, who presumably only had access to primitive photometers. By Aitken’s time however, technology had improved considerably and on page 168, we are informed that his contemporaries could measure dips lower than 0.1 stellar magnitudes. Aitken then provides an overview of the various models developed just a few years earlier by the pioneers in this field; Henry Norris Russell and his assistant, Harlow Shapley, then at Princeton University.

Chapter VIII deals with the actual determination of stellar masses, again a matter of some technical difficulty. Aitken assumes the reader is familiar with the basic principles, citing relationships without proof. Here, we shall work through the simplest example; that of a pair of stars in circular orbits, the orbital plane of which lies along our line of sight.

Consider a system consisting of two stars seen edge on, M and N, orbiting their common centre of gravity C , at a distance x and y metres, respectively, from C.

The problem is illustrated here:

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Star N experiences a centripetal force given by Fn = NVn^2/x. Star M experiences the same centripetal force given by MVm^2/ y, where Vn = the velocity of star N about C, and Vm is the velocity of star M about the same locus, C.

But the velocity of each star can be expressed as the circumference of the orbit divided by its orbital period, p:

Vn = 2.pi.x/p and Vm = 2.pi.y/p
So squaring these expressions gives Vn^2 = 4pi^2x^2/p^2 and Vm^2 = 4.pi^2y^2/p^2
Thus, we can express the centripetal forces as
Fn = 4 pi^2 Nx/p^2 and Fm = 4pi^2My^2/p^2
By Newton’s third law we have;

Fn = Fm

Hence , we obtain Nx = My
Or N/M =y/x ( Eq1).

This important result states that the ratio of the masses in this binary system is given by the ratio of the distances of each component from the centre of mass at locus C. But we have two unknowns here, so we require another equation to solve for both stellar masses.

Let the sum of x and y be a, the linear distance between the centres of the stars.

So x + y = a
So x = a –y
And since x =My/N and y = a-x, we have x = M(a-x)/N
So M(a-x)/N = x
(Ma-Mx)/N =x
Thus x = Ma/(M+N) (Eq2)
Finally, equating the gravitational and centripetal forces
4 pi^2 Nx/p^2 = GMN/a^2
Substituting the expression for x in Eq 2 gives:

p^2 = 4pi^2 a^3/G(M+N)
So M+N = 4pi^2 a^3/Gp^2
This is one form of Kepler’s third law ( or the harmonic law as referred to by Aitken)
If we choose to express the period in years, the masses (M and N) in solar masses and the distance, a, separating their centres in astronomical units (AU), the relationship simplifies to:

M+N = a^3/p^2 ( Eq 3)

So using Equations 1 and 3 (the ratio and sum of masses, respectively), double star astronomers can work out the masses of both components.

Although we may observe the period, p, directly from measurement, we need to convert the angular separation in arc seconds, a”, so that Eq 3 is modified to:

M + N = [(a”/pi”)]^3/p^2.

Note that this is only the simplest system to analyse. In reality, astronomers are often not sure about the inclination of the orbit from our line of sight nor its eccentricity. This is discussed at great length in Chapter V and VI.

This method works well for systems whose distances are known using trigonometric parallax. But how does one come up with a way of finding the ratio of the stellar masses as shown in Eq 1? Fortunately, there is a straightforward way to do this that involves  the redshift results mentioned earlier.

Picture the pair of stars once again, orbiting the common centre of gravity (barycentre) in simple, circular orbits as before. If high resolution spectra are obtained of the two stars as they orbit the barycentre, and accounting for their natural proper motion as they orbit the Galactic centre, the astronomers would obtain a curve showing how their radial velocities change as a function of time. These will be sinusoidal curves (at least in this simple case) with different velocities but, crucially, exhibiting the same period.

From our previous considerations, we can equate the periods of both stars about the barycentre.

Thus p = 2piy/Vn = 2pix/Vm
Thus y/x = Vn/Vm

And from Eq1 we already have y/x = N/M

So, we arrive at the eminently useful result:

N/M = Vn/Vm (Eq 4).
Simply put, the ratio of the masses of the component stars of a binary system is in the same proportion to the ratio of their radial velocities about the barycentre.

Putting it all together; two relationships enabled double star astronomers to deduce the mass of both components of a binary star system. These involve their mass sums and ratios.

M + N = a^3/p^2 (where a is expressed in AU, M & N in solar masses, and p in years).
N/M = Vn/Vm.

A worked example will help firm things up.
Consider a binary system, seen along our line of sight, with a measured orbital period of 10 years and have measured radial velocities of 10 and 20 km/s. If 5 AU separates the pair, find the individual masses.

M + N = 10^3/5^2 = 40
N/M =10/20 = ½

So 2N =M and substituting this result into the first equation gives
2N + N = 40
So 3N = 40, thus N = 13.3 solar masses.
M is given by 40 – 13.3 = 26.7 solar masses.
In this way, the successful coupling of the spectrograph to the classical refractor enabled the masses of the distant binary stars to be divined.

Sums and ratios.

And the structure falls.

Man and his symbols!

Chapter VIII ends with a discussion on specific types of star. On page 219, Aitken opens up with a fascinating remark made with respect to the Cepheid variables;

The Cepheid variables entered in Table II have been omitted from the later tables because, considered as binary systems, they seem to belong to a class by themselves…..

Aitken outlines the problems in interpreting Cepheids as a type of eclipsing binary star and concedes that some astronomers had questioned whether the observed spectral line displacements were attributed to bona fide orbital motion. Certainly, no mathematical model based on binary star orbits could adequately match their observed properties, as Aitken acknowledges. That said, he asserts on page 220 that this was a minority opinion:

The majority of astronomers, however, still hold to the opinion that they are binary systems.

The regularity of the light curves of Cepheids were found to match their radial-velocity curves almost perfectly. Subsequent studies of the light amplitude of Cepheids showed typical variations between 0.5 and 2 magnitudes in visible light and velocity amplitudes in the range 30-60 km/s. The first Cepheid velocity curves were measured toward the end of the nineteenth century and at first were assumed to be the result of orbital motion. Only after more of their ‘orbits’ had been computed that it would became clear that they were physically implausible..

Aitken goes on to say that:

some astronomers have raised the question whether the observed line displacements in the spectra of these stars really indicate orbital motion in a binary system or whether they may not have their origin in physical conditions prevailing in the atmospheres of single stars.

The pulsation hypothesis gained increasing acceptance after 1910. Sir Arthur Eddington’s theoretical work from 1917 onwards showed that Cepheids are single stars that undergo radial pulsations because they function as enormous heat engines. The radial velocity curves of Cepheids represented the expansion and contraction of the star via a mechanism known as an Eddington Valve. This is caused by differences in opacity between singly and doubly ionised helium, which causes the star to undergo cyclical heating up, expansion, cooling and eventual contraction under gravity.

In calling our attention to Table XII, Aitken does show that Cepheids all appear to have later spectral types – F and G – whereas those of visual and eclipsing binaries were scattered across the entire spectral sequence; a point of interest no doubt, but Aitken does not see much significance in it.

Aitken’s belief that Cepheids were a type of eclipsing binary star might also explain why he does not mention the work of Ms. Henrietta Leavitt, who uncovered a curious relationship between the Cepheid’s absolute visual magnitude and its pulsation period. Her work was published in preliminary form as early as 1908 – fully ten years before Aitken’s book – and in more robust form in 1912. That said, it is evident that other astronomers, most notably Harlow Shapley, was using Leavitt’s discovery to develop the first standard candle to measure distances far beyond that which could be achieved (at the time) using trigonometric parallax.

The final chapters of the book  (IX, X and XI) deal quite a bit with more speculative aspects of binary and multiple star astronomy. In Chapter IX, Aitken describes what is known about some of the more famous double stars in the sky. In Chapter X, he uses tables to illustrate how the numbers of double star vary by spectral class, distance, mass distributions and so on. Aitken cautions that these data is a work in progress though, and that future surveys would show up more comprehensive statistical results. For readers who may find this kind of work of interest, this author would recommend the later book by Dr. Paul Couteau: Observing Visual Double Stars (1984), where a greater number of pairs are analysed in a similar way. These data show that over half of all stars in the Galaxy are either binary or belong to multiple star systems. It is most interesting that although measuring techniques had improved in the generation of astronomers after Aitken, the same instruments were used to make those measurements.

The subjectivity of star colours is also mentioned in passing by Aitken on page 264. In particular, he notes that Professor Louis Bell (author of the respected book on telescope optics), had noticed that when two stars of unequal magnitudes were seen close together, the fainter member was, more often than not, reported as bluish in colour and, in general, had little to do with its actual spectral class. As ever, we tend to think of these issues as being contemporaneous, but a little digging tends to show that they have their precedents in the literature of earlier generations.

The final chapter delves into the curious question of origins: specifically, how do binary and multiple star systems come into being?

Aitken briefly discusses three theories of ontogeny:

1. The capture theory: where one star captures another while passing too close to it at some time in the past.

2 The fission theory: where a single star in the process of forming divides into two or more smaller fragments, which in turn evolve into bona fide stars in their own right.

3. The fragmentation theory, which holds that  two or more fragments ‘condense out’ from a single cloud of gas and dust, and which later evolves over time to produce a new binary or multiple star system.

Aitken concedes that all of these theories have merit  and discusses the astronomers who originated these models. Suffice it to say that the chapter makes for fascinating reading in the 21st century!

What the book means to double star observers in the 21st century;nothing new under the Sun!

The determination of the orbital elements of binary stars involves quite a bit of mathematical analysis. But unlike today, the professional astronomers of yesteryear, together with their assistants, had to make do with primitive calculating machines, slide rules and the like, in order to carry out their complex calculations. Today, computer programs make much lighter work of this.

A question for modern graduate students: can you follow the mathematics covered in this book?

We have seen how the classical refractor reached the theoretical limit of its resolving power, even in the larger apertures. Despite the advent of more exotic types of glass (short flints and the like) in the early twentieth century,  the astronomers did not feel the need to upgrade them in any way. Self evidently, this would have been overkill; cheap and cheerful crown & flint was more than up to the task. For example, why haven’t the double star astronomers using the 26 inch Clark at the US Naval Observatory ‘upgraded’ the object glass with FPL 51 or FPL 53 or some such?

Because it is not necessary to do so!

The current obsession with small apochromatic refractors is entirely an amateur phenomenon; a solution looking for a problem.

The work described by Aitken in this book should provide a lot of encouragement to those who wish to take up the fascinating hobby of double star observing. If the large classical achromats could reach their resolution limits, so too can their modern equivalents, especially in the smaller apertures available on today’s market. These days, small achromatic refractors are available for very little money and other (equally ergonomic) designs show great promise even in larger apertures e.g, the Maksutov and Schmidt Cassegrains, as well as the venerable Newtonian reflector (preferably f/6 or slower).

Last but not least, the work described in this book reminds us that no matter how well informed we think we are today, our forebears never ceased to come up with ingenious solutions and amazing surprises.

They too were people, just like you and I.

We can still learn something from them today.

Nota bene:

A 1919 review of the Binary Stars

A 2007 review of the same text.

De Fideli