Review of: The ShortTube 80 Telescope: A User’s Guide by Neil T. English

This book was kindly donated to SAS by Mike Geisel in November 2019, and is another volume of the prolific Patrick Moore Practical Astronomy Series. This is a first edition, published by Springer in 2019, so it should be quite up-to-date. A nice point is the small number of typos; many other first editions have much more.

After the usual front-matter (Preface, Acknowledgements etc) are the thirteen chapters of the text:

1 Under a Dark Sky 2 Anatomy of a ShortTube 80 3 Mounting a ShortTube 80 4 Exploring the Deep Sky 5 Improving the High-Power Performance of the ShortTube 80 6 Watching the Sun 7 Exploring the Moon and the Planets 8 Exploring the Realm of the Double Stars 9 The Meade EXT 80 10 Imaging with the ShortTube 80 11 Souping Up the ShortTube 80 12 Founding Days 13 Afterword: The Little ‘Scope that Could

Index

The first chapter (Under a Dark Sky) is a tour (perhaps a real single night, maybe a composite spread over months or years) of celestial objects which are suited to a small refractor, viewing in mid- October. The Author includes open star clusters, emission nebulae and larger galaxies, as well as the waning crescent Moon rising in the east in the wee-small hours, but no planets. The author mentions less-familiar objects such as Collider 70, an open star cluster, better known as the sprinkle of ~140 mostly 6th - 9th magnitude stars centered on Orion’s Belt, and including the three 2nd magnitude Belt stars. The Collinder (1931) and Melotte (1915) Catalogues each contain a few hundred bright open clusters, typically a few tenths of a degree wide. Many appear on both Catalogues. Here is a new resource for wide-angle telescopes. There is a category of telescope called the Richest-Field Telescope (RFT) which is ideal for such wide-angle objects. The ShortTube 80 approaches RFT parameters... more later.

The location given for the tour is Scotland, and the Author lives in Glasgow, which has a latitude a little south of 56° N, so many of the objects viewed are unfamiliar to us SE Queenslanders (27°-28° S); the difference is about 84°. With this reservation, the tour is a good flavour of the ShortTube 80’s forté. Chapter 2 (Anatomy of a ShortTube 80) as its title suggests, walks the reader through the “anatomy” (or architecture?) of the ShortTube 80, sometimes nicknamed “Shorty”. A brief list of specifications is: 80 mm aperture air-spaced conventional achromatic doublet, and 400 mm focal length, for f/5 focal ratio. This combination of features gives wide-angle performance that is difficult to achieve in other inexpensive telescopes. This chapter reveals a slight misnomer in the book’s title... The ShortTube 80 is a specific model (no longer in production) sold by Orion. Several retailers sell telescopes with similar optical parameters, and the Author includes these variants under the “ShortTube 80” name. Many versions are packaged with inexpensive entry-level accessories such as a 90° star diagonal, a 25 mm eyepiece (16X), and a 10 mm eyepiece (40X). Some come in a hinged aluminium-look hard case with sculpted foam to protect the contents. A 1.25-inch rack-and-pinion focussing tube is the usual type. Many are packaged for retail sale with a cheap alt-az mount. (The most common version is probably SkyWatcher’s SW804AZ3S model, packaged with a findersope, 45° diagonal, 10-mm and 25-mm eyepieces, and mounted on their AZ3 alt-az mount.) Some versions of the ShortTube 80 are of reasonably high quality; the basic optical system or Optical Tube Assembly (OTA) is often the strongest link in the package. To make them compact, many versions have a slide- back retractable (metal) dew shield, and a long focusser travel. Many have a metal front end-cap that screws into the dew shield; probably all include a plastic dust plug for the focusser. Some have a built-in or attached dovetail for mounting; this might be too short if you change the telescope’s balance by using heavy after-market eyepieces, especially 2-inch ones, in combination with a matching star diagonal. It may be necessary to buy a longer dovetail bar and tube rings to suit.

I have experience with a refractor of this class... the Prostar 80 was sold (but is no longer stocked) by MyAstroShop for various prices in the $AUD 350-450 range. Mine was an OTA (no diagonal, eyepieces, finder-scope or mount, but it included a zippered black canvas-style padded carry-bag with handles). It has a 2-inch Crayford-style two-speed focusser; and the bag is roomy enough to hold a few accessories such as a star-diagonal and an eyepiece or two. I wanted the 2-inch focusser, because some of my eyepieces are 2-inch only (others are dual-diameter), purchased specifically for my other telescope, a 1970’s orange Celestron-8; and I didn’t want to buy a set of quality 1.25-inch eyepieces too. There is sufficient travel in the focusser to accommodate the longer length of a 2-inch diagonal, as well as the shorter mechanical length of a DSLR camera adapter. Its characteristics using my eyepieces are as follows:

Eyepieces parameters: Focal length Apparent FOV Power True FOV Exit pupil Baader Hyperion aspheric 36mm 36 72 11 6.48 7.2 Masuyama 26mm 26 85 15 5.53 5.2 Meade MWA 15mm 15 100 27 3.75 3.0 Meade MWA 10mm 10 100 40 2.50 2.0 William Optics XWA 5mm 5 110 80 1.38 1.0

The Southern Cross is 6.00° tall, the Pointers are 4.38° apart; and targets such as the Hyades (face of Taurus the Bull), Orion’s Belt plus Sword, and each of the Magellanic Clouds (Small Cloud plus globular cluster 47 Tucanae) fit inside the view circle if I use my Baader Hyperion aspheric 36mm eyepiece. My eye-pupil diameter of 5.5 mm in effect “stops down” the 80mm lens to 63mm with this eyepiece; this costs ~0.5 magnitudes in the faintest star visible. My Masuyama 26mm eyepiece is a good match for my fully-open pupil; and captures all of the above deep sky objects, except the Southern Cross (just missing the foot), and it misses either one star of Orion’s Belt (δ Orionis), or the tip of his Sword – but captures M42, with all of the Belt.

The author also mentions that this style of telescope is very good as a spotting scope for observing targets like birds. For nearby objects, the focus position will be outwards from the position needed for astronomical subjects. Different models may have different outermost focus positions; something that should be assessed according to your requirements.

A further use is as an autoguider for astrophotography through a second imaging telescope. Modern CCD guiding cameras are so sensitive that you might not need the light-gathering power of an 80 mm telescope, and a smaller dedicated autoguider would work well or better; but if you don’t need one, why spend the extra money?

Author Neil English says that the ShortTube 80 is also good for solar observation using a front-end solar filter. I’m confident that this would be so, but I haven’t tried it; solar viewing generally doesn’t interest me, except for rare events like transits of Mercury (and Venus).

As English points out, most telescopes in this class can be upgraded with after-market accessories... Crayford-style dual-speed 2-inch focusers, premium eyepieces, high-reflectance diagonals, German equatorial mounts etc. But if you can afford a large portfolio of improvements, then a higher-quality OTA such as an ED doublet, or a triplet might be a better investment; these have special expensive glass in the objective. An 80 mm ED doublet or triplet OTA sells for ~$AUD 1200 -2500 but a suitable package might be negotiated at a good price. Beware of “putting lipstick on a pig”, by trying too hard with a ShortTube 80.

English takes the reader through the suitability of several aftermarket high quality eyepieces, and warns against using eyepieces with very long focal lengths. The issue is the wide-open size of the user’s eye-pupil. If the telescope’s exit pupil exceeds the observer’s eye pupil, the effect is as though the 80 mm diameter is “stopped down” in the ratio of eye pupil ÷ exit pupil. The corresponding light ratio is in the ratio of the squares of the two diameters, and that amounts to a specific loss in magnitude of faintest star visible. If the diameter drops to 72 mm, the loss is ~0.2 magnitudes; for 64 mm the loss is ~0.5 magnitudes. The compromise is minimal, unless you need to see the very faintest stars accessible, or the very finest detail. I think English exaggerates the issue.

The Author next discusses the chromatic aberration found in such a telescope. (ED doublets and triplets are much better colour-corrected, so chromatic aberration is less obvious in these more expensive telescopes.) There are various ways to reduce the effects of chromatic aberration... a light yellow Wratten #8 filter, or minus-violet filter; otherwise, use a more expensive interference filter specially designed for the purpose, variously named Semi-Apo, Fringe Killer or Contrast Booster. All of these reduce light transmission by 50% or more, causing a loss of ~0.75 magnitudes (or more) of faintest visible star. Compare English’s positive attitude about chromatic aberration filters with his concerns about losing light through using an eyepiece with a “too-long” focal length! The adverse effects of chromatic aberration in images can be reduced by appropriate image-processing. Also, for faint primary targets, the faint chromatic ghosting may be invisible.

Chapter 3 (Mounting the ShortTube 80) is a discussion of suitable ways to mount a ShortTube 80. Depending on the model, and accessories being used, a ShortTube 80 weighs about 2.0 - 3.5 kg, and this sets a lower limit on the load capacity of the mount. Another factor to consider is the mode of operation. Daytime spotting, vs visual astronomy, vs astronomical imaging; there are plusses and minuses for alt-az and equatorial mounts. An alt-az is better for daytime spotting and casual wide- angle visual browsing; equatorial mounts are better for targeted a list of visual objects, and probably necessary for imaging faint objects. If an interest in photography means that you have a sturdy tripod already, try it with your telescope; that may suffice for your style of viewing. Alt-az options include GoTo tracking versions that are especially useful for viewing selected targets in the sky. Going very fancy with the mount risks falling into “lipstick on a pig” scenario.

Another option is an alt-az table mount. This would (if shake-free) be a good option for bird- watching from the patio or verandah. Another good option is a dedicated astronomical alt-az mount such as the SkyWatcher AZ3, which has a nominal load capacity of 4.5 kg, and is bundled with a matching aluminium tripod that has adjustable legs. Typical prices are $AUD 100 – 200. (I sometimes use one of these, improved by epoxying the upper and lower leg fittings into the tripod legs, filing the upper leg fittings to better match the mount’s head, and stiffening the leg brace by drilling a hole through the accessory tray, and putting a bolt with wing-nut through this hole. I tighten and loosen the altitude axis to suit with a 19 mm socket on a ratchet handle; and I use the legs unextended, except to level the tripod head.)

A small German equatorial mount is another option; most have a useful load capacity of 5 kg or more. Prices start at about $AUD 350. An interesting version is the SkyWatcher Star Adventurer, which costs about $AUD 600 or more as a package, and has a load capacity of 5 kg. The system is modular, and various components can be included or omitted as required. The unit is especially useful for photography with a conventional DSLR camera and lens (including telephoto lenses up to about 300 - 400 mm focal length; but will carry a small telescope (visual or imaging) without difficulty. It will track in Right Ascension, but there is no provision for tracking in Declination, so polar alignment needs careful attention. There is a smaller version, the WIFI Mini, which is less expensive, but has a nominal capacity of 3 kg. Depending on the version of telescope and the accessories used, the telescope may be over 3 kg.

The Author also discusses ways of mounting a ShortTube 80 piggy-back style on a larger telescope, as a finderscope, an autoguider, or to supplement the larger telescope’s narrow view with a wide- angle view through the smaller refractor.

The fourth chapter (Exploring the Deep Sky) starts in a well-tried way. Beginning with an explanation of star magnitudes, it moves on to discussing absolute magnitude. Next come a few paragraphs on vision of the eye, followed by advice on dark adaptation, which is fairly thorough.

A page or so explaining Declination and Right Ascension is followed by a detailed account on star- hopping with the finder scope. Most of this is good, with one minor slip... In describing what stars you might see in the finder scope the Author introduces the Bortle Scale of sky brightness/darkness, and its influence on the faintest star visible to the unaided eye. He appears to transfer this concept to the view through the finder, suggesting that stars fainter than 5th magnitude won’t be visible. This is wrong... a small finder scope will show stars to 8th magnitude, and stars down to 7th magnitude may be useful for identifying faint targets, although brighter stars are more useful (if available).

The Author reminds the observer that the optics may flip the view; and his comment that a star- diagonal will cause a left-right swap, but leave the view upright is very timely. Too many writers either simply say that the view will be flipped, without being specific; or else go into a confusing account of all possible combinations of up-down ± left-right inversion. He also is a little off the mark in reminding the user that it is likely that more stars will be seen in your telescope than your star atlas shows, because “... most atlases only present stars down to magnitude 7...” Several atlases go fainter, and many planetarium programs have the facility to print maps that include very faint stars.

The next few pages suggest various eyepieces to use on various types of targets. There seems to be no brand bias here; specific Celestron, Meade and Explore Scientific eyepieces are recommended, as well as premium Tele Vues. There is even a muted “lipstick on a pig” warning, softened with the comment that expensive eyepieces can also be used in any other more-expensive telescopes that you might have.

Following this is a brief account of a few types of variable stars, but no mention of other types of deep sky objects (clusters, galaxies, nebulae etc), before describing other aspects of observing such as the Celestial Sphere, when and where to observe, atmospheric seeing, and sketching what you see. The section on variable star types is all good, but a bit out of place here, especially in the absence of summaries of other types of objects. (The ShortTube 80 is well-suited to several types of variable stars, with its reach down to faint stars, combined with a wide view that can include appropriate comparison stars in the same field of view.) One rare point of careless explanation is seen here (on p56). English describes the brightness variation of Algol; his wording “... it goes back to normal again after another 5 hours...” could be easily misinterpreted as a sudden increase 5 hours later, rather than a continuous gradual rise over the following 5 hours. As a refreshing nod to the southern hemisphere observer he mentions Cepheid variable 1 Carinae on p58; but this is a typo, the correct name is l Carinae (that’s lower-case “ell”, not “one”). Another minor typo appears on p58; recurring nova T Pyxidis is printed as “T. Pxidis”.

One nice touch is the smooth flow of subject matter from novae, to the need for nova-hunters to know the night sky very thoroughly, to a detailed description of the Celestial Sphere, which is well- done... neither too simplistic, nor so detailed that you would get lost.

The following section on when and where to go observing, deals with the usual subjects... strong light pollution near population centres, bright moonlight interfering with viewing, and the effects of the seasons on weather. There is also the useful advice that the naked eye appearance of the Milky Way is a good indicator to the clarity of view to expect through the telescope. The Author also reminds us that the Moon, the planets, and double stars are not so obscured by light pollution as are other targets. Two points not on a Queenslander’s mind are; firstly, snow is common on the ground in Scotland and Scandinavia in winter and this reflects light up into the sky; and secondly the sun never gets far enough below the horizon in summertime to “switch-off” the twilight in Scotland and Scandinavia.

This is followed by a few comments on seeing, which relates to the steadiness of the image, as a reflection of the homogeneity (or otherwise) of the air you are looking through. There is no mention of transparency which is just as important, especially in SE Queensland; where smoke, dust, and thin high cloud are important factors in reducing contrast in the view. Many other books share this imbalance in commentary between seeing and transparency.

The section on sketching your view is conventional. An important point not mentioned is that the illumination required for sketching is at odds with the level of emphasis the Author places on dark adaptation. And, for some observers, sketching just isn’t their “... cup of tea...”.

The next section (almost fifty A5 pages) is a list of targets favourable to a small refractor such as the ShortTube 80. There is a paragraph or two on each target, and a few sketches and photographs. The arrangement is “through the seasons”, starting with the Northern Hemisphere spring. Within each season the arrangement seems a bit haphazard. Although targets near to each other in the sky are grouped generally on adjacent pages, every so often the order switches to Right Ascension sequence. For example, during Northern Hemisphere winter pages, targets in the Auriga-Gemini area are grouped together, then the focus switches south-eastwards along the Milky Way to the Monoceros-Puppis-Canis Major, jumps back to Gemini for a few targets, then returns to the Monoceros-Puppis Canis Major area (but including the very out-of-order NGC 457 in Cassiopeia).

Naturally this is the personal list of an observer living in Scotland, but there are a few rather southern objects in Sagittarius and Scorpio. There is little information about finding these targets, except by “star-hopping” from a prominent starter star. The Author seems reluctant to depart from the Bayer Greek letters to select starter stars for star-hopping to the targets. In some constellations, several faint stars are tagged with the same Greek letter (e g Psi Aurigae: ψ1 ψ2 ψ3 ψ4 ψ5 ψ6 ψ7 ψ8 ψ9 ψ10) [ψ10 Aurigae is now 16 Lyncis] but English calls the starter star for a couple of his targets “Psi Aurigae”, without mentioning which of the ten he means. There are other similar examples. For some targets, the starter star he uses is quite faint and obscure, and he ignores alternative starter stars that are brighter and easier to identify. There are no finder charts or R A & Dec co-ordinates. For these you need to go elsewhere, such as an atlas or catalogue. Maybe this is a good thing, because the glossy pages of this book would be damaged easily by dew, so it is not really a book to keep open beside the telescope. Unfortunately, the light required to read carefully a star-hop description is bright enough to compromise dark adaptation.

One interesting touch is the inclusion of not-so-well-known objects from the Melotte and Collinder catalogues. These list several hundred open clusters, many of them bright and so large that they “overfill” the field of view of many telescopes. These targets are better-suited to binoculars, or a ShortTube 80 with a long focal length eyepiece. Examples are the Hyades (Melotte 25), the sprinkle of stars including and surrounding the Belt of Orion (Collinder 70), and The Coathanger asterism (aka Brocchi’s cluster) in Vulpecula (Collinder 399). Another set of targets described is various pairs and trios of galaxies, including M81 + M82 in Ursa Major, and two Leo trios; M95 + M96 + M105, and M65 + M66 + NGC 3628. Naturally, English has included several small objects as well, such as double stars Albireo (β Cygni) and Polaris A & B, variable star Y Canum Venaticorum, and several planetary nebulae.

I checked the locating instructions for each of the targets in this chapter against Taki’s 8.5 Magnitude Star Atlas and/or Cartes du Ciel planetarium software. (I assessed the finding instructions for a Northern Hemisphere observer. Southern Hemisphere readers will need to adjust up-down and left-right as required.)

There are issues with the descriptions of many of the targets:

On p 67, the locating instructions for Messier 81 & 82, an Unlikely Coupling involve using Phecda and Dubhe, stars in the Big Dipper of Ursa Major. There is no information for identifying which stars of the Big Dipper these two are.

On p68, the full instructions for finding Messier 64, the Black Eye Galaxy are: “You can find it by imagining a line between the Beehive Cluster (Melotte 111) and Alpha Coma Berenices.” Yes, but there is no information on what to do with this line! Also, the Beehive is incorrectly named as Melotte 111, which is the Coma Berenices cluster. The Beehive is actually Melotte 88; but that designation should be “at the back of the queue”. Other designations of the Beehive that take precedence are M44, NGC 2832 and Praesepe. A better instruction would be: “Look 10° southeast from the centre of the Coma Berenices cluster (Mellotte 111)”. Praesepe is irrelevant to finding M64, being almost 60° away from the target. The finding instructions have been hopelessly tangled up by the Author.

On p69, the instruction for locating Messier 88 & 91 is “...pan 8 degrees west-northwest of third magnitude star Eta Virginis.” (η). The panning instruction is correct, but the starting point is wrong; you need to begin at third magnitude Epsilon Virginis (ε); (and Eta is actually fourth magnitude, not third). Evidently, English confused Epsilon (ε) and Eta (η).

On p70 the instruction to locate Messier 68 is “...3.5 degrees south-southwest of Beta Corvi.” The correct direction is south-southeast.

Also on p70, English describes Y Canum Venaticorum, La Superba, a deep red variable star that ranges in magnitude from +4.8 to +6.3. The Author comments that by noting the brightness of surrounding stars you can monitor the changes in the variable, but there is no information on these comparison stars. He tells you what to do, not how to it.

On p71, in the description of Messier 3 there are said to be “several thousand” globular clusters (in the Milky Way Galaxy, or in the Universe?). The true number known in the Milky Way Galaxy is ~150, with perhaps another 20-30 not yet found.

Also on p71, in the description of Messier 13, Jewel of the Northern Sky, the sentence: “M13 lies about 23,000 light years the Solar System.” lacks the word “from”. Also, the finding instruction “...in the upper right corner of the keystone asterism...” is misleading. A better description would be “...one-third down the right side...” (for the northern hemisphere). Finally, the description “...the finest globular cluster visible from the northern hemisphere.” is not quite correct. Omega Centauri and 47 Tucanae are the finest globulars in the sky, and are visible from low northern latitudes.

On p 73, there is no instruction for finding galaxy Messier 49, other than saying it is in Virgo (the second-largest constellation!). In passing it is said to belong to the Virgo Cluster of galaxies, but this comment does little to pin down the location. The best guide is to say that it is “...on a line between Beta and Epsilon Virginis, slightly closer to Epsilon”. On p74 (A Trio of Galaxies in Leo), instructions for finding the trio mention “...a line running between Chertan and Regulus.” There is no other designation given for the former star, which is actually θ Leonis, but who would know that “off the top of the head”?

Also on p74 (Another Trio in Leo), the finding instructions begin: “Start at Theta Leonis (Chort)...”. The previous reference to Chertan is ignored, but at least this time Chort is identified as Theta Leonis. According to Wikipedia; Chertan is derived from Arabic and means “two small ribs” (δ & θ Leonis); and Chort is Arabic for “small rib” (θ Leonis). The “two small ribs” later became “the back” (Zosma, δ Leonis) and “small rib” (Chort, θ Leonis), with Chertan then as an alternative to Chort.

Again on p74 (M63, a Sunflower in the Sky) English mentions that the target is “...about 1 degree north of the 5th and 6th magnitude stars 19 and 20 Canes Venaticorum.” A better instruction would be “... about 5 degrees northeast of 3rd magnitude Alpha...”

There is a minor typo also on p 74 for Messier 97, the Owl Nebula: for “planetary nebula”, substitute the plural “planetary nebulae”. (English uses “nebulae” for the plural, rather than “nebulas”.)

On p77 (Messier 101) the second sentence reads: “Although stated at as an 8th magnitude galaxy,...”. Apparently, English changed from “at” to “as” or vice versa, but forgot to delete the original word.

NGC6826, the Blinking Planetary (p78) isn’t easy to find. The Author’s instruction is to look about half a degree east of 6th magnitude wide double star 16 Cygni. Iota Cygni is 4th magnitude and easier to identify; look for NGC8626 just under 3 degrees southeast of Iota.

On p79, Messier 39 is said to be about 10 degrees northeast of Deneb. “East-northeast” would be a better description.

Also on p79 (NGC 7000, the North America Nebula), the Author uses a term in a misleading, unconventional way. He suggests “Charging your ShortTube 80 with its lowest power, richest field eyepiece...”. The term “richest field” is applied to telescopes in a specific way: a Richest Field Telescope (RFT) is a specific matched combination of the diameter of the telescope’s objective, the objective’s focal length, eyepiece focal length, observer’s pupil diameter, and star count (numbers of stars of various magnitudes). It takes more than an eyepiece to make an RFT. (If you remove an eyepiece from an RFT, and put it in a telescope with different optical parameters, the new telescope doesn’t become an RFT.) That said, an 80mm f5 telescope with a 35 mm eyepiece is richest field for someone with 7 mm eye pupils; but for someone older with 5.5 mm pupils (like me) the RFT would need a 27.5 mm focal length eyepiece. (I come close with my 2-inch Masuyama 26 mm eyepiece. My 36 mm Baader Hyperion eyepiece doesn’t make my ShortTube 80 an RFT, because my pupils are smaller; the equivalent telescope is a “ShortTube 63”, which loses about 0.5 magnitudes in light grasp from the full size of 80 mm. All the faintest stars disappear, and the view is no longer richest field. It’s not all a waste though, I like to have the extra-wide view when I want it, and the 36 mm eyepiece is really good in my other telescope, a Celestron-8, which I owned before I bought “Shorty”. The C-8 would be RFT for 7 mm pupils with a 70 mm eyepiece; for me with 5.5 mm pupils it would be RFT with a 55 mm eyepiece, which I don’t own – probably ~ $ AUD 350 for a TeleVue 55 mm Plössl. The 36 mm eyepiece also makes the C-8 close to RFT when I use my 0.63X focal reducer/field flattener; for which the ideal would be a 35 mm eyepiece.)

On p80 (The Veil Nebula), English treats the terms “Veil Nebula” and “Cygnus Loop” as synonyms. In earlier times (mid- to late-20th Century) the overall system was called the Cygnus Loop, and the Veil Nebula was the two bright segments on the east and west edges of the Loop.

Also on p80 (NGC 6992, the Brightest Section of the Veil); this target is not done well at all. NGC 2992 is correctly described as the eastern and brightest side of the Veil. English says “You should also be able to see NGC 6995.” This would be true, but he does not identify which part of the Cygnus Loop is NGC 6995! He also writes about “The western side of the Veil Nebula...” as a visible component, but doesn’t give its NGC number (NGC 6960).

On p81 the instructions for finding Messier 11, the Wild Duck Cluster could be better... English says pan southwestwards to a semicircle of stars (but he omits the distance, it’s about 18 degrees). He says to then move “...a little south...”, but “...3 degrees further southwest...” would be a better description.

There is another interesting target on p81, which is Messier 6, the Butterfly Cluster (on p80). About 4° away to the SE is Messier 7, considerably brighter than M6, but not included in English’s list of targets. M7 is about 2½° further south than M6; from Glasgow, M6 is 88° from zenith at its culmination, M7 is 91° from zenith (1° below the horizon). It makes sense to exclude something 1° below your horizon, but why include something that never rises further than 2°? It seems like the list of targets has been chosen (or partly so) by declination limits, rather than by the view in the telescope. Also, the viewing time for M6 is Northern Hemisphere summer, when evening twilight merges with morning twilight in Scotland; at an elevation of 2°, the view would be horrible.

On p82 (Messier 14) is said to be about 6.5 degrees south of third magnitude Gamma Ophuichi. Gamma is actually fourth magnitude (3.75); and the direction is more like south- southeast. A better starter star would be third magnitude Beta Ophuichi; M 14 is about 8 degrees to the south.

Also on p82 (NGC 6633), this open cluster is identified as “...about 8 degrees west of the 4th magnitude star, Theta Serpentinis...”. The cluster is about the 10° east of 3rd magnitude Beta Ophuichi, a starting point that is much easier to find.

On p83 (Messier 25), English writes that M25 “... is just under 4.5 degrees east of 4th magnitude Mu Sagittarii.” This instruction would not find M25; the direction should be “northeast” in order not to miss the cluster from a starting point at Mu Sagittarii.

On p83 (Messier 17, Omega or Swan Nebula) English identifies this old favourite, and on p84 he introduces open cluster Messier 18 which is only 1° south of M17 (which he mentions). These targets could have been treated together as a remarkable double-target (like the Leo trios).

On p84 (NGC 6572) the starting star is magnitude 4.6 star, 71 Ophuichi. The target is said to be about 2 degrees south (actually, south-southeast). A better starter star would be magnitude 3.7 star, 72 Ophuichi; NGC 6572 is 3 degrees south-southeast.

Also on p84 (Messier 24, the Small Sagittarius Star Cloud) the Author refers to this target as an asterism, which it is not. M24 is a part of one of the arms of our Milky Way Galaxy. An asterism is a pattern of stars (not-necessarily related by astrophysical parameters) that is a part of a constellation. Examples are the “Saucepan” of Orion, the Square of Pegasus, Brocchi’s Cluster/the Coathanger/Collinder 399 in Vulpecula; and the “Big Dipper” of Ursa Major.

Also on p84 (Messier 16, the Eagle Nebula) the Author follows the modern trend to name this object after the nebula. Messier saw this as a “Cluster of small stars, mingled with a faint light... with a weak refractor it appears in the form of a nebula.” (Translated, from the Atlas of the Messier Objects.) Messier 16 was actually a cluster for late 19th - early 20th observers.

Again, on p84 (Messier 55) is included as a target. The Author tells us that it is of magnitude + 6.3. And: “From a good dark site, it ought to be just visible to the naked eye.” But not from Glasgow, where it would culminate only 3° above the horizon, especially in the Northern Hemisphere summer, when evening twilight merges in morning twilight. The account seems made-up rather than based on his observations. Incidentally, M22 (also in Sagittarius) is one magnitude brighter at +5.2, and more northerly (10° elevation at culmination at Glasgow), but is not included as a target. And I have seen M22 naked eye from various locations in Qld, NSW & WA. Also M4 isn’t included; its magnitude is +5.4, it would rise to 7½° at Glasgow, and its location in Scorpio so close to Antares makes it much easier to find than M55. It too is naked eye at a dark location, but a little more difficult than M22. (I have never tried to see M55 naked eye, so I can’t comment on its naked eye visibility from my own experience.) Interestingly, M55 does not appear as an Index entry; this appears to have been a slip-up by the Author, because most (all?) of his other Messier targets are indexed.

On p85 (NGC 6819) the Author says “The eye is fooled into seeing a ‘V’ shape from its brightest luminaries, which caused some observers to name it the Fox Head Cluster, but it is hard to see how it even remotely resembles a vixen. What do you think?”. I’ve never looked at this in the sky, but have examined several on-line images. There is definitely what you could call the “back-end” of the V, but not the “point” (i e there are two short non-parallel lines). That much is real, it’s not the “eye being fooled”. But I agree with English that making a fox head out of it is going too far.

Also on p85, NGC 6871 is said to be about 2 degrees east of Eta Cygni. A better direction would be east-northeast.

On p87 (M45, the Glorious Pleiades) contains a misuse of the word “epicentre”, as in: “...radiating outwards from its epicentre.” The Author should have written “centre”; “epicentre” means something else. “Epi-“ is a prefix meaning upon or over. An epitaph is written upon a tombstone; the epidermis is the skin layer over the dermis; and an epicentre is the place on the Earth’s surface over the focus of an earthquake (the point underground where the rock had fractured).

On p88 (Melotte 25, the Hyades cluster), the Author repeats the notion of “richest field eyepiece”, suggesting a 34-mm Explore Scientific Maxvision 2” eyepiece. The concept is really richest field telescope, a matched combination of objective’s diameter, objective’s focal length, eyepiece focal length, and eye pupil diameter.

On p90 (Stock 23, Pazmino’s Cluster) there is a typo: the statement “...less than about 5.5 degrees of Eta Persei...” is missing the direction “northeast”.

On p91 (NGC 1342) directions to this cluster are given from 3rd magnitude Epsilon Persei; it’s also the same distance southeast from 2nd magnitude Beta Persei, which is easier to find.

A comment on Messier 33, the Pinwheel Galaxy on p91... this is visible with the naked eye from a dark site (I can confirm this). For most people, M33 is the most distant naked eye object, at 2.73 million light years (Mly) away (the Andromeda Galaxy is 2.54 Mly). (A few people claim to have seen M81 without optical aid... for them the naked eye distance limit is 12 Mly; but for most people M81 isn’t naked eye. M81 is at Declination ~+81°, about 8°-9° or more below the horizon from SE Qld.)

On p94 (M27, the Dumbbell Nebula), the finding instructions are incomprehensible. A useable scheme is: Identify Albireo (β Cygni) and the Coathanger; then make an equilateral triangle based on them, pointing to the east.

On p95 there is no information to identify the multiple-star target 31 Cygni. It is about 5 degrees west-northwest of Deneb, and is also known as Omicron1 Cygni.

Likewise on p96, there is no information to identify famous double-star 61 Cygni. It is about 8 degrees southeast of Deneb.

Also on p96 NGC 7662, the Blue Snowball the singular “...planetary nebula...” should be plural “...planetary nebulae...”. The location is given only as in Andromeda near the border with Lacerta. The easiest finding instruction is 14 degrees west of M31 (the Andromeda Galaxy).

On p98 (Messier 42, the Great Nebula in Orion), the first sentence is garbled: “Easy to find as a large foggy patch in the sword handle of Orion, this is the celestial Hunter.” Clearly, M42 is not the celestial Hunter, as this sentence literally implies. Also, M42 is about halfway between Orion’s Belt and his feet (Rigel & Saiph); a sword handle would not be so low; this nebula must be in the blade or rather, the scabbard. (The traditional description of certain stars as Orion’s Sword is wrong.... it must be really the scabbard, presumably holding his sword, or maybe empty.) English mentions the “...famous Trapezium (Theta 1 & 2 Orionis), a lovely quarter...”. The Trapezium is Theta 1, consisting of a multiple star (actually a small open cluster in the brightest part of the nebula): Theta 1A, 1B, 1C & 1D are visible in small telescopes such as the ShortTube 80; larger telescopes reveal extra stars... E, F, G, H1 & H2, and G. Theta 2 is a different star, about 2 arcminutes from the Trapezium, but still enveloped in M42. Finally, “quarter” should be “quartet”.

Also on p98, (M43) is in the same low power field as M42, and the two targets could have been treated together as a double target.

On p99 (Collinder 70), the cluster centered on Orion’s Belt (and including the three stars) is in the same very low power field as M42 & M43.

On pp99-100 (NGC 1981) the bright cluster north of M43 is in the same very low power field as M43, M43, and Collinder 70.

On P 100 (M35) the direction is missing from the finder instructions; “...about 2.3 degrees of the comely orange star Eta Geminorum.”. The missing direction is “east”.

Also on p100 (NGC 2395) is said to be “...just shy of 4 degrees southeast of Lambda Cygni.”. That should be “Geminorum”. Actually, this cluster is also about 5° north of β Canis Majoris, which is easier to identify than λ Geminorum.

On pp100-101 (M36, M37, and M38: A Trio of Messier Open Clusters in Auriga) these three clusters are lumped together as one target; but they span about 6°, too much to see in one view, except in telescopes with an unusually wide view (using a long focal length eyepiece that has a very wide apparent field of view). It really should have been split into three targets.

On p 102 (NGC 2281) this cluster is said to be “... 0.8 degrees south-southwest of Psi Aurigae.”. Unfortunately, there ten 5 th-6th magnitude stars called Psi Aurigae... ψ1 ψ2 ψ3 ψ4 ψ5 ψ6 ψ7 ψ8 ψ9 & ψ10, none of which are easy to identify. (Actually, ψ10 is now 16 Lyncis.) It would be easy to locate β Aurigae and α Geminorum (Castor), and search just north of the midpoint of the line joining these two stars.

On p103 M46 is just over 1° from M47 on p102; the two could have been combined as a double target.

Also on p103, M48 is said to be south of Zeta Monocerotis; it’s actually south-southeast.

On p105 (NGC 2383) the instruction for finding this cluster is “...less than 6 degrees east- northeast of the 3rd magnitude star Omicron Canis Majoris”. There are two stars called ο Canis Majoris, 4th-mag ο1 & 3rd-mag ο2. It would be easier to imagine the line from ε Canis Majoris to δ Canis Majoris, and extend it two more times. (Both stars are 2nd magnitude.)

Also on p105 (NGC 2384) the finding instruction is “...move your telescope about 8 degrees... (from NGC 2383)...”; the amount should be 8 arcminutes. NGC 2383 & 2384 are so close together they should be considered as a double target. Indeed, the instruction “move” is hardly appropriate.

Also on p105 (NGC 2395), in Gemini there is a comment that “(NGC 2395) is noticeably larger than NGC 2384 and NGC 2383...”. This target immediately follows NGC 2384 & 2383, so it is clear that the Author intends the observer switch back to Gemini, after observing in Monoceros-Puppis-Canis Major. The observing sequence is intentional, not accidental.

On p106 (NGC 2362), the observing sequence switches back to Canis Major, after two targets (NGC 2395 & 2420) in Gemini.

Also on p106, (NGC 2420) (the next target after NGC2362), it’s back to Gemini. This target was described on p105 in similar wording!

Also on p106, (NGC 2423) (next after NGC 2420), its back to Puppis for an open cluster only 0.8° from M47, described four pages earlier on p102!

Again on p106, (NGC 457, the E. T. Cluster) the next target listed after NGC 2423 is in Cassiopia, which is north of Andromeda; so this description belongs back on about p90, somewhere near the description of M31-M32-M110.

On p107 (NGC 2237-9, the Rosette nebula/Caldwell 49), it’s back to Monoceros. The Rosette is quite dim visually (but spectacular in CCD images). Open cluster NGC 2244 is immersed in the nebulosity, and a lot more prominent visually. Its separation from marker star Epsilon Monocerotis is said to be “...a few degrees”; actually, about 2 degrees.

On p108 (NGC 2236), the Author’s comment “While you are in Monoceros...” shows that he is recommending a specific sequence of observing targets, a sequence that jumps around inconveniently. Also, the target is said to be northerly from marker star Epsilon Monocerotis; it is actually northeasterly.

Again on p108 (NGC 2302) another comment demonstrates that he recommends a specific observing sequence (that jumps inconveniently): “Yet another open cluster in Monoceros...”.

Also on p108 (NGC 2169) the finder instructions begin with Xi and Nu Orionis, which are two barely 4th magnitude stars in Orion’s Club. The observer is asked to imagine a third point forming an isosceles triangle with Xi & Nu, to find NGC 2169. There are two such possible third points, but English does not indicate which one. The one to choose is southwards towards Betelguese. Also, the triangle is better described as right-angled, with the target at the right angle.

Also on p108 (Messier 41), it is worth mentioning that this cluster is a naked eye object.

On p109 (NGC 2281) is a repetition of the same target as on p102, but with different wording. Once again the starting star is given as Psi Aurigae (which of ψ1 ψ2 ψ3 ψ4 ψ5 ψ6 ψ7 ψ8 ψ9 or ψ10? − ψ10 is now 16 Lyncis). Here, he refers to about “...10 (stars) that form a distinctive parallelogram shape.”; on p102 he comments on “...the pretty little quartet of stars at its centre.” This is an example of the Author getting lost in his own words.

On p110, NGC 2266 is said to be “...1.8 degrees north of ... Propus (Eta Geminorum).” It is actually north of Metsuba (Epsilon Geminorum)! This is another example of English being confused between Epsilon – ε and Eta – η; repeating his confusion between Eta and Epsilon Virginis in his locating instructions for Messier 88 & 91 on p69.

One noticeable anomaly is the shortage of variable stars in the list of deep sky objects, given that the Author spent almost three pages describing them, especially certain types of variable stars (Observing Variable Stars with the ShortTube 80 on pp 55-58). Only two are included on the list, and these as much for their intense red colour, as for their variability. There are several other variable stars of less spectacular colour that could have been included... β Persei (Algol), and δ Cephi are obvious examples; both are easy to find, are of naked eye brightness, and the changes can be seen in less than a week.

English even puts forward the ShortTube 80 as a candidate to use for a Messier Marathon; a single one-night session where the observer sees all 110 Messier objects. The time of year (late March to early April at New Moon time), time of night (evening twilight to morning twilight), and viewing sequence all need careful planning. The Messier Marathon is possible only between 55° N and 20° S latitudes, and is best between 35° N and 10° N, because of the range of Declination of the targets. Interestingly, the Author does not refer to any successful Marathons using a ShortTube 80 or similar telescope. A quick search on-line suggests that most attempts are made with 200mm - 300mm class telescopes, and I didn’t find anybody claiming success with an 80 mm telescope, but success is plausible. (Messier’s favourite telescope was an 89 mm f/12 Dollond achromat of 120X, not much different in capability from a ShortTube 80.)

Chapter 5 (Improving the High-Power Performance of the ShortTube 80) opens with a slightly garbled sentence, talking about the basic eyepieces usually supplied with a ShortTube 60: “... usually a 25-mm low power unit and a 10-mm high power unit per ocular.” The last two words should be removed.

The discussion of chromatic aberration on p114 is a little misleading: achromatic objective lenses “...cannot adequately focus blue-violet and longer red wavelengths well.” This is not true; they might be able to focus these wavelengths perfectly, but not at the same location as the green and yellow wavelengths for which the objective is optimised. There is sensible advice about dealing with chromatic aberration: put up with it; use an appropriate filter; or stop the lens down to say 60 mm or even 50 mm, which would drop the f-ratio to f-6.7 or f-8 respectively. Contrast this recommendation with the Author’s warnings about very long focus eyepieces essentially “wasting” aperture by making the exit pupil larger than the observer’s eye pupil. Still, a piece of cardboard with a 50- or 60-mm hole cut out is cheaper than a long focal length eyepiece.

These 50- and 60-mm aperture-stops will lift the faintest magnitude reached, by 1.0 or 0.62 respectively. Light pollution filters will cost ~0.5-0.6 magnitudes also. Reducing the aperture will reduce the resolving power proportionally, while light pollution filters don’t. The most significant aspect is the brightness or dimness of your target. Bright targets like the Moon or planets will show strong colour fringes, but it doesn’t matter if you use a filter or aperture that dims the image a small amount. If the target is very faint, and you need every photon you can get, then any colour fringe will be undetectable, so you won’t need any light absorbing filter or light blocking aperture-stop.

English then goes into more detail on light pollution filters. There is also a reference to the Sirius Optics Minus Violet filter, which is probably what is called the Sirius V Block Violet Reduction Filter in Australia. The text of this section generally is good, but there are a couple of problems with the figures... Fig. 5.3 concerns the effects of filtering-out certain wavelengths of light; perhaps the Author couldn’t find an appropriate diagram, so he drew what he wanted in pencil on a piece of paper out of a loose-leaf binder (three holes), and photographed it on his table. This didn’t really work; the result is almost unreadable (lines and text insufficiently dark and bold). He also refers to a comparison between various types of filters designed to suppress the effects of chromatic aberration: “As you can see from the light transmission curve for this filter shown here...” but there is no Fig. Number, and no diagram either; it was left out. Fig 5.7 shows two filters held side-by-side against the sky, with the comment in the caption that “The Baader 495 yellow long pass filter (left) has high light transmittance...”but there is no identifying comment about the other filter shown.

English explains the effect of stray light reflections in the telescope that will degrade its performance, and recommends blackening the edges of the objective lens of the telescope. This advice is good, but requires that the lens be dismantled, something that some people wouldn’t want to tackle. He also refers to flocking, which is low-reflectance self-adhesive material that you can apply to the inside of the telescope tube to reduce contrast-reducing reflections. It can also be applied inside the dew shield (which will then be no longer retractable).

A final section on collimation is flawed. He recommends using a Cheshire collimating eyepiece to check if the telescope’s components are “lined-up”. Any misalignment can probably be alleviated by tweaking the screws that hold the focusser. This is good advice. However the caption of the Fig. 10 inappropriate: “A Cheshire collimating eyepiece helps you center the lens elements of the ShortTube 80 telescope for optimal performance at high magnification.” No, the procedure described in the text was aligning the focusser... the lens elements of the ShortTube 80 cannot be adjusted sideways to centre them!

Chapter 6 (Watching the Sun) has a well-chosen title... sunspots and prominences change the appearance of the Sun, so it can be watched, rather than being looked at. After the expected warning (in CAPITAL LETTERS) about the potential for damaging your vision by looking directly at the Sun through an optical device, the Author describes the various techniques for safe observing. This chapter is good... well written, accurate, and comprehensive.

The first technique mentioned is solar projection, onto a screen, or into a home-made box to exclude stray light. English includes a simple formula for calculating the position of the screen to give the required image size; this is a nice touch. He reminds the observer about the Sun’s rotation, and the way this makes the sunspots appear to move across the Sun’s disc; and also summarises the typical pattern of growth and decay of sunspot groups. He suggests collecting a batch of your sketches and flipping through them to simulate an animation; the same could be done by scanning each drawing, and assembling the batch of scans into a slide-show or video clip.

Another accessory for viewing the Sun is a full-aperture filter that fits over the telescope’s lens hood/dew tube. The simplest type can be made from Baader AstroSolar film, mounted in some sort of home-made frame that goes over the front of the telescope. Contrast in the resulting yellow image can be enhanced using a green Wratten #58 filter screwed into the front of the eyepiece. Thousand Oaks, Orion and Celestron also make full aperture front-end solar filters (there may be others as well).

Another (rare) accessory is the Herschel wedge, a tapered wedge of glass. Most of the light refracts through, and goes safely away out of a port in the housing; about 4.6% reflects off the front surface of the wedge (the tapered shape prevents interference from multiple reflections, which would result if the glass had parallel faces). This low fraction (4.6%) is still too high, and must be further attenuated somehow. The market for Herschel wedges is tiny, and they need to be very well-made if they are to work well, so they are very expensive, and difficult to find.

Baader also makes Solar Continuum filters in two sizes (1.25-in & 2-in) that screw into eyepieces. These must be used with some other device that attenuates the overall light (full aperture filter or Herschel wedge), and they transmit a small “slice” of the Sun’s spectrum around 540 nm, which is in the green part of the continuum; the narrow slice is between (and avoids) any dark absorption spectral lines. Coincidentally, the narrow slice avoids any chromatic aberration issues, which arise because of the wide spread of wavelengths arriving from astronomical objects. An achromat (e g ShortTube 80) is just as good as a more expensive ED or apochromat.

The ultimate accessory is a narrow-band energy-rejection filter that passes just the H-α emission line at 656.28 nm in the red part of the spectrum. These are very expensive, and the devoted solar observer should consider strongly getting a dedicated solar-only telescope such as one of the Coronado or Lunt units, which have this type of filter built-in.

All of these light-reducing accessories are useful for viewing the Sun during solar eclipses; or transits by Mercury, Venus, and the International Space Station.

Chapter 7 (Exploring the Moon and the Planets) starts with the Moon in a fairly conventional way... a brief summary of its probable mode of formation, early history, and its current drift away from Earth. The Author mentions the orbital period of the Moon, (about 27 days), but surprisingly, doesn’t mention that the cycle of phases takes longer (about 29½ days) or why that is so. After a brief description of the phases (New Moon, First Quarter etc), and the appearance (crescent and gibbous shapes), he gives a good daily description of prominent features, especially those near the terminator – the line dividing dark from bright. The descriptions are good, and appropriate to a small refractor. There is a minor typo on p142; “...on the sunward plane annexed to Copernicus.” I don’t know what is “sunward”, but I suspect that English means the sun-lit side away from the terminator, and surely “plane” should be “plain”.

The next section describes observing and timing lunar occultations. The Author describes the procedures, except how to access an accurate time signal. He tells the reader how it’s done, not how to do it.

The title of the next section is quite appropriate (Jupiter Watching), because Jupiter “does things”, many of which can be seen easily in a ShortTube 80. A carelessly worded sentence on p145 may mislead the reader... English is writing about observing targets when they are close to our sky’s meridian, and you are looking through less air than when Jupiter (or other targets) is lower in the sky; which he has written as “...when observed at lower altitudes.” There is a possibility that “altitude” may be misinterpreted as closer to sea-level, rather than closer to the horizon. Another issue is the comment that some oppositions are better than others, because Jupiter is higher in the sky. This effect is not explained; the Ecliptic is not referred to anywhere in the book leading up to this page. There is not even an unexplained account of the circumstances of good oppositions (good oppositions are in a certain season, i e in Winter, when the Sun is low in the sky, and the opposition position is correspondingly high in the sky).

On p127, the Author describes the bands of Jupiter, but omits one of the main ones: he starts with the dark North & South Equatorial Belts (NEB & SEB), then comments “Between these dark belts lie large, brightly colored zones.” He next lists the zones and belts outside of the NEB & SEB, but omits the Equatorial Zone (EZ), which is the one between the NEB & SEB. English describes the famous Great Red Spot, and mentions that many observers are unable to see it with their ShortTube 80 telescopes. He suggests using a Baader long pass filter be used, to darken it against the rest of the planet. In principle, any filter far from red (green or blue) should be useful.

The description of the different rotational zones (System I encompassing NEB & SEB, and System II elsewhere) contains a passing reference to “the equatorial zone”, without stating that it is a formally named band, the Equatorial Zone (EZ). He refers also to mutual events between the four Galilean satellites, including the situation where one hides behind another (as seen from Earth); he calls this a satellite eclipse. Actually, a satellite eclipse is the situation where one of the satellites disappears because it has passed into Jupiter’s shadow; English is describing a mutual satellite eclipse. The Author also doesn’t mention occultations (where a satellite disappears behind Jupiter’s disc (as seen from Earth); or transits, where a satellite passes across Jupiter’s disc (as seen from Earth).

Following Jupiter is a section on Saturn. The Author mentions that Saturn looks small compared with Jupiter. Saturn’s disc generally appears about the ⅓ width of Jupiter, but the angular span across the rings is not much smaller than Jupiter’s angular width. English describes well the features visible in a small telescope such as the ShortTube 80.

In the section on Mars, the Author mentions the few features that you might see with a small telescope; polar ice caps, Syrtis Major, and obscuration of details by dust storms. He reminds us that Mars varies greatly in angular size around opposition. He could also have mentioned that oppositions vary significantly because Mars has a decidedly elliptical orbit... its distance from Earth at opposition ranges between ~56 000 000 km and ~102 000 000 km.

For Venus, the only features visible in a telescope are the size and phase (crescent, gibbous etc). Like all targets, Venus is best seen when far above the horizon, (i e in daylight). As a diversion, English reminds us that Venus can be used to demonstrate the chromatic aberration of typical of small f- ratio achromatic telescopes!

English tells us in the next section, about Mercury, that surface features can be seen on Mercury during moments of good seeing, and drawing these is a worthwhile activity, although he doesn’t explicitly state that these features are visible in a ShortTube 80. He reminds us that the view is best in daylight (when Mercury can be high above the horizon), and that darkening the sky with a polarising filter is useful for both Venus and Mercury. He suggests that if you have a Meade EXT80, to do a two-star alignment at night, set the mount in “parking mode”, and re-activate the telescope the next day, when the mount will go to the position of Mercury, and begin tracking. English does not mention Uranus or Neptune, which are easy to see in a ShortTube 80, but there is little to observe. Their moons are too faint for this size of telescope.

Rather strangely, comets are not mentioned in this chapter or elsewhere. The famous 18th Century comet discover and observer Charles Messier owned and had access to several telescopes. His favourite was like a long version of the ShortTube80; it was an 89-mm f/12 achromat, which he generally used at a magnification of 120X.

The eighth chapter (Exploring the Realm of the Double Stars) begins with a summary of the methods used to observe double stars, and a historical perspective, including a reference to the Dawes limit of a telescope’s resolution when observing double stars. One strange aspect is that the Author refers to the Pickering and Antoniadi scales of seeing (“calmness” of the air column you are looking through), but doesn’t explain the various levels on scales of seeing, even though he advises including the seeing conditions on the Antoniadi scale when you log your observations. You need to go elsewhere to find a description of these two scales of seeing.

English next recommends cutting out some circular apertures in cardboard (25mm, 40mm, 50mm & 60mm) to experiment with, testing the capabilities of the telescope on some carefully selected double stars, with equal-brightness pairs, and pairs of unequal brightness.

Next come several pages of easily-resolved double (and multiple) stars, then more pages of difficult doubles and multiples. Once again there are no details for locating them; you will need to look them up in an atlas, or a catalogue to get their R A & Dec. For almost all, only the host constellation is mentioned, either implicitly in the star’s name (e g 61 Cygni); or explicitly, where the star designation doesn’t name the constellation (e g Struve 331 in Perseus).

There are several issues with this section; the list is very disorganised; and for most examples where the separation is large there is no number in arcseconds given, only the comment “wide away”. The three fundamental parameters for observation of multiple stars are: magnitudes of the components, separations of the components; and angular bearings of the fainter components with respect to the brightest. These shouldn’t be omitted (except perhaps for the relative bearings), or downgraded from numbers to descriptive relative terms.

Detailed commentary is warranted:

The first double (p160) is a nod to the Southern Hemisphere – Alpha Centauri, which has a declination of ~61° S, so it is ~27° or more below the horizon for Glasgow.

On p163 the descriptions jump around all over the place... Alpha Capricorni, then Epsilon Canis Majoris (visible in a different season), then back to Beta Capricorni, then away to Delta Corvi, and then back to Omicron Capricorni, (where the magnitudes of the components are unusually omitted).

On p165 the three Capricorn doubles are described again (this time including the magnitudes of the two components of Omicron Capricorni).

On p166, Albireo isn’t further identified as β Cygni, nor is it said to be in Cygnus.

On p170, (Kappa Puppis) the title is in a different font name and font size, and is in upright letters not italics, unlike all the other description titles.

Also on p170 (36 Ophuichi), the magnitudes of the components and their separation are omitted, although their distance from us, and their period of mutual orbit is included.

On p171 (Delta Cephei) is included as a double star. Its variability isn’t mentioned (it is the type example of Delta Cepheid variables), nor is it included in the earlier group of deep sky objects in Chapter 4.)

On p172, there is no angular separation given for 5 Lyncis, 12 Lyncis, or Sigma Orionis.

Also on p172 is (Struve 2816), for which the constellation (Cepheus) is not mentioned. It is said to be very close to the open cluster Trumpler 37; in fact this star is the brightest member of the cluster, and as the two are at similar distances, the star is probably a true member, not just coincidentally in the foreground. If coordinates of the cluster are hard to find, look up nebula IC 1396; Trumpler 37 is immersed in it; and a famous dark globule, the Elephant’s Trunk Nebula (IC 1396A) is also in IC 1396.

On p173 (Zeta Sagittae) the Author says that the components “... can be resolved at medium powers...”, so this is not “wide away”; however there is no number given for the separation.

On pp174-175 a further inconsistency of style is revealed: the separation of 90” is given for 16/17 Draconis; 231” for Alpha Librae; and 58” for Iota Librae. Specific separations are given for these, not just “wide away”. The next target (Gamma Equulei) doesn’t give a magnitude for the ‘secondary’ (curiously, the word is surrounded by single inverted commas – not quote symbols), and the separation reverts to the “...not far away.” style.

The second list (of “difficult” doubles) is done better, but there are a few problems here too:

On p176 (Epsilon Persei), no suggestion of separation (qualitative or qualitative) is given, beyond the suggestion of using a power of 80X or so, implying that the stars are well- separated. Indeed, the difficulty is stated to be due to the difference between the two components, given as + 2.9 and “exceedingly faint”. Why not just print the magnitude number?

Also on p176, (Castor (Alpha Geminorium)) there is no hint of the brightnesses of the two components, nor even whether they are similar or noticeably different.

On p177, the Author uses an unconventional naming of a double star: Sirius B (The Pup). Usually, multiple stars are designated by the brightest component. The title of this description should be either Sirius, or Sirius A & B, or Sirius and the Pup. There is no guide to the separation beyond the recommendation to use “...high powers (100X or so)...”. The apparent (and true) elliptical orbit means that the separation varies over the stated 50.1 year period, but there is no hint at the components’ separation at the time of publication (2019). On p178 (Mu Cygni) the target is not a true binary, but rather an optical double (a coincidental near-lineup of two stars widely separated in space, rather than in mutual orbit). Even so, the separation should be given as a number, not just “...very close-in...”.

Also on p178 (Mu Librae) the “secondary” is said to be “...wide...”, and difficult to see, because of its faintness. English recommends raising the power to 150X to 200X, and trying to separate the “secondary” into two components. No numbers are given for magnitudes or separation. But the implication is that the two fainter stars are separated somewhere near the Dawes limit, around 1.47” for an 80mm telescope.

On p179 (Iota Cassiopeiae) the separation of the secondary from the primary is not given as a number, but “...tucked up right beside it.”

Also on p170 (Gamma Delphini) the only hint of separation is “...resolvable ... above 100X”.

On pp179-180 (Rigel (Beta Orionis)) the separation is “...very close...”; powers above 100X are suggested. There is no quantitative separation given.

On p180 (Delta Cygni) the need for “...very high powers (approximately 200X)” is mentioned, but no number.

Also on p180 (Delta Geminorium), after six targets with only qualitative separations given, numbers come back for this binary.

On p181 (Zeta Ursae Majoris (Alula Australis)), the quantitative separations are dropped for “... very tight system...” The separation will increase gradually until about 2035, when the stars will close up again – but no numbers are given.

Also on p181 (Gamma Virginis (Porrima)) the separation is “...very tight...”, with a recommendation for “...high magnification (150 to 200X).” No number.

At the bottom of p181 (Alpha Scorpii (Antares)), the only hint of separation is the suggestion for “...high powers.”

Chapter 9 (The Meade EXT 80) is an account of one popular packaging of the ShortTube 80. In the late 1990s Meade introduced the EXT 90, a 3.5-inch f13 Maksutov Cassegrainian telescope. After a few years they brought refractors into the concept package... EXT 60, EXT 70, and EXT 80 telescopes.

Chapter 9 concentrates on a version called the Meade EXA Backpack Observatory. This was an 80mm f/5 achromatic refractor mounted in an alt-az fork mounting on a light tripod. The mount is controlled by a go-to hand controller; and two Meade Superplössl eyepieces, a 26-mm (15X) and a 9.7-mm (41X) are supplied. The diagonal is built-in, quite appropriately for a telescope where the back-end becomes inaccessible between the fork tines when the telescope is pointing near zenith. The diagonal mirror can be flipped out of the way, for attaching a camera. There is also a 3X Barlow (giving 45X and 123X depending on the eyepiece) that can be slipped into the light path. An extra 45° upright-image terrestrial diagonal is also supplied. The package came with a bespoke back-pack and an instructional DVD. The total weight (excluding AA batteries to power the mount) is 5.3 kg. One issue with the unit that English points out, is that it is aimed at the beginner market; but to do a successful star alignment you need a reasonable (more than beginner) knowledge of the night sky, to make sure the unit is pointing at the right alignment stars. The unit is really more useful to the advanced amateur than the novice. The field of view with the 26-mm eyepiece is about 3°, which is a bit tight for use without a finder, and there is no easy way to mount an after-market finder. A 32- mm Plössl (~4° FoV) eyepiece is a useful extra, to assist in finding targets.

English reports that the performance is quite good, even with the original eyepieces. He is rather disappointed with the list of double stars in the auto-controller’s database. Users can add their own favourite targets to the database already installed by Meade.

Chapter 10 (Imaging with the ShortScope 80) comes next. We have an instance early in the chapter of the Author’s flowery prose leading the reader astray: “Over the years, astro-imagers had discovered that the faster the focal ratio of the imaging system, the shorter the exposures they had to make...” Not really, this was old knowledge from the earliest days of photography, applied to film photography through telescopes and “portrait lenses”. Another (small) blunder is on p192, where English suggests hooking up a CCD camera to a “Shorty”, and a high f ratio telescope to see how rapidly or slowly the image goes in and out of focus as you view the TV monitor; surely he means computer screen?

The Author suggests on p192 that the telescope be left to “acclimatise” to ambient temperature, before you start to image, lest thermal contraction shift the system out-of-focus. The effect is real;

Depth of focus Δf = ± 2λ(f-ratio)² (for λ/4 wavelength error).

For f-ratio of 5 and wavelength of 550 nm (green); Δf = 27.5 μm

Coeff of linear thermal expansion of aluminium (typical telescope tube material)

≈ 21-24 ppm per K°, or about 5-6 μm per degree (K or C), over the length of a ShortTube 80 (~ 250-300mm).

If the telescope is about 4-5C° above ambient, it will shrink about Δf during cooling.

There is an explanation of how f-ratio affects exposure times in the last paragraph of p192, which would have been good, but for an unfortunate typo... for an f-15 vs f-5 telescope, the image on the focal plane is spread over an area “... nine times (15/5) larger...”; but the squared superscript has been left off: it should be “....nine times (15/5)² larger...” The conclusion that “Faster ’scopes require shorter exposures.” is valid, of course.

At the top of p193 is another small mistake... the ShortTube 80 is called a telephoto lens (in the context of connecting it to a camera). The “telephoto lens” is a specific optical system designed to shorten the physical length of the lens, but preserving its optical length. The front elements are over-converging, and the rear elements are relatively diverging (you can see the diverging elements at the back of any telephoto lens). The text goes on to describing digiscoping, which consists of attaching a mobile phone or tablet to a holder that positions its lens in-line with the telescope’s optical axis, allowing the user to take photos. There is a range of holders to allow for the different sizes of phones and tablets, and also their different architectures, which governs camera position in the phone or tablet. It is also possible to mate a point-and-shoot or DSLR camera to a telescope.

One important issue is camera shake... most mobile phone and tablet cameras “take the shot” by a tap on the screen; but this could shake the set-up and blur the image. Fortunately, many of these phones have a delay “self-timer” mode to allow the photographer time to tap the screen, and then move into the scene. This is also sufficient delay to allow vibrations from tapping the screen to die out. There is also scope to use a Bluetooth remote release that shoots immediately, but is physically isolated from the phone or tablet. The Author then appears to stray beyond the limits of his knowledge. He mentions that some phones do not have high grade software (true), and recommends downloading apps like Photopills (actually PhotoPills) or the Photographer’s Ephemeris (actually The Photographer’s Ephemeris) to improve the situation. These apps aren’t upgrades to the phone/tablet software; they are mainly aids to imaging composition, and cover aspects like sunrise/sunset time and direction, moonrise/moonset time and duration, twilight duration, azimuth and angle of the Sun and Moon etc; with facility to determine other parameters, such as recommended exposure times, depth-of-field of lenses, angular coverage of lenses etc. English says that “...Photopills (sic) is often regarded as a top photography app for iPhones, and the (sic) Photographer’s Ephemeris is suitable for Android devices.” Actually, PhotoPills is a splendid app on my Android phone, but the Android version of The Photographer’s Ephemeris (TPE) has been given such poor reviews that I haven’t downloaded the paid version, and I haven’t seen the iPhone version in action. (The free Windows version of TPE is rather limited, but OK for freeware.)

The Author’s Digiscoping Tips begin with a misleading suggestion... that the weight of the camera plus holder may cause the camera to sag a bit, and this can be corrected by adding weights to counterbalance the camera/holder combo. If the camera is actually sagging there’s a problem where the focusser joins the telescope tube, and you may need to adjust the alignment, or upgrade the focusser; counterbalancing is futile. Alternatively, if it’s actually the camera-end (i e the rear end) of the whole camera/holder/telescope system that’s sagging, counterbalancing will work (beware of adding so much weight that you “overload” the mount enough to degrade its performance). An alternative is pushing the dovetail forward on the mount (if that’s how your telescope is mounted) to re-balance the system.

The second paragraph, about shutter speed, exposure mode and ISO refers to daylight terrestrial photography, and is not really relevant to imaging deep sky objects at night. English doesn’t make this very clear. He has some other good tips... If focussing is difficult, use the camera’s auto-focus. Heat-shimmer (the astronomer’s “seeing”) is severe in hot weather, try digiscoping in the cool of the morning. Take plenty of photos; you can always reject failures later... film is cheap in digital cameras.

In the next section (Using the ShortTube 80 as a Guide ‘Scope for Astrophotography), the Author wastes almost a full page explaining manual guiding through a piggy-back guide-scope (in 2019!); then moves on to autoguiders, particularly the Orion Compact 80 Telescope (CT) autoguider package. The Orion StarShoot AutoGuider fits into the focusser, and contains a CMOS sensor. Movement of the guide-star image on this sensor is converted by the software (installed in a computer that connects to the AutoGuider) to signals that nudge the main mount in the direction required to keep the main telescope pointing correctly. (English doesn’t mention the electronics involved.) The total weight is only 1.7 kg (3.8 lb). English also repeats the statement in the Orion web-brochure that the Orion AutoGuider is unsuitable for Schmidt Cassegrain telescopes, without mentioning why. The problem is in attaching the dovetail bar to the cylindrical tube of the SCT. The solution is to attach an appropriate extra dovetail bar to the top of the SCT, and attach the AutoGuider dovetail bar to this; some drilling and tapping of threads in the dovetail bars may be involved.

English doesn’t mention an excellent alternative... put a small inexpensive stand-alone CCD camera in the focusser and drive the guiding with free software such as PHD2 (Push Here Dummy 2).

English also mentions ways to image through the ShortTube 80, using an H-α filter to eliminate chromatic aberration; or by mounting a smaller guide-scope on the Short-Tube 80; or by mounting the Shorty on a larger telescope which acts as the guide-scope. Chromatic aberration (C A) in the images can be reduced using editing software that includes an appropriate C A correction module. The Author also reminds the reader about stacking short sub-exposures.

English also reminds the reader of the importance of dark, transparent skies. The ShortScope 80 in skilled hands will produce better images than top-end instruments used poorly.

Chapter 11 (Souping Up the ShortTube 80) is about adding accessories to the ShortTube 80. The first accessory English deals with is the finder. Many versions of the telescope come with an empty finder shoe, ready for a red dot or Telrad or magnifying (mini-telescope) finder-scope. The Author does not like red dot style finders, and claims they are not much good for anything fainter than 1st magnitude, but my experience is that they are useful even down to 3rd magnitude, where there are plenty of stars sprinkled across the sky. He recommends a 6X30 magnifying finder-scope (typical example’s weight 122g/4.3oz) (i e 6X power, with a 30-mm front lens), and worries that an 8X50 finder-scope’s weight (typical example 462g/16.3oz) may be a problem for either the telescope (extra vibration), or the mount (strain). The weight difference between typical 6X30 and 8X50 finders is significant – 340g/12oz). I generally use a red dot finder on my ”Shorty”; if I want more magnification or a fainter magnitude reach, I borrow the 8X50 right-angle finder off my C-8, unless I am using the “Shorty” piggy-back style on the C-8, then it stays mounted on the C-8. The 8X50 is an upgrade of the C-8’s original 6X30 straight-through finder-scope which was mounted to the SCT using two machine screws, and has a curved base that doesn’t fit the standard finder shoe on the “Shorty”, so I can’t attach it easily to my refractor.

Another improvement recommended by English is a Crayford-style dual-speed focusser. My Starpro was equipped with one of these when I bought it. One of the crucial selling points for me was the capacity to take 2-inch eyepieces (and 1.25-inch eyepieces with the adapter supplied). I already had bought 2-inch eyepieces for my Celestron C-8. There are also single-speed Crayford-style focusers, which are less expensive than dual-speed ones, but probably still better than the original rack-and- pinion unit.

One by-product of a 2-inch focusser (Crayford-style dual-speed or otherwise) is the capacity to accept a 2-inch diagonal; this is physically bigger than a 1.25-inch diagonal, so the eyepiece will sit further back from the objective, and give a closer nearest-focus position. This can be handy for spotting, especially nearby wildlife in daylight. The Author also recommends blackening the edges of your lens elements, and flocking the telescope tube; both actions will reduce stray light that reduces contrast in your view or images. Both procedures were mentioned in Chapter 5 (Improving the High-Power Performance of the ShortTube 80); for the edge-blackening there is more detail in Chapter 5 than here (including pictures), and for flocking there is more detail in Chapter 11 than in Chapter 5. In Chapter 11, English adds the suggestion to flock inside the focusser tube as well as the main telescope tube, and to blacken the tips of any screws that protrude into the telescope’s interior. Interestingly, there is no cross-reference in either chapter to the other, nor is either process mentioned in the Index. When you re-assemble the focusser back into the telescope tube you can check the “tension” of the focusser for ease-of-movement

He also repeats the recommendation to check the alignment of the focusser, and adjust this if necessary. This was also covered in less detail in Chapter 5 (but with a photograph there of the Cheshire eyepiece used to check the alignment). Once again, neither chapter refers to the other about the process, nor does the Index mention “collimation” or “Cheshire eyepiece”.

A further recommendation is to upgrade the original inexpensive 1.25-inch diagonal (especially if you now have a 2-inch focusser) with a 2-inch that has a very flat ⅟₁₀-⅟₁₂ - wave mirror with a high- reflectance dielectric coating (99% reflectivity claimed, rather than 85%, worth about 0.16 magnitudes). There are also 1.25-inch dielectric-coated ⅟₁₀-⅟₁₂ - wave diagonals for telescopes without a 2-inch focusser.

There is even more choice for the terrestrial spotter – 60° and 45° diagonals for the two sizes, in various quality levels. These are designed for terrestrial spotting, and don’t switch the image left-for- right (true view). Unfortunately most of these terrestrial diagonals usually don’t work well at high powers; or very low powers either, when they vignette the outer rim of the field of view.

This chapter contains advice about eyepieces that partially repeats advice in Chapter 5. English’s advice to try (at star parties and field nights at your local astronomy club) before you buy. He doesn’t recommend specific eyepieces here. He reminds the reader to make sure that the eyepieces you choose also fit your other telescopes.

The Author makes more specific recommendations for Barlow lenses, particularly recommending the Celestron Ultima 2X Barlow, and the Orion 2X Shorty. Barlow lenses increase the eye relief of the eyepieces installed in them; but Tele Vue Powermates don’t. Powermates come in two magnifications, 2.5X & 5X (and 2-inch & 1.25-inch versions) and are quite expensive. Tele Vue also make high quality Barlow lenses, in 2X and 3X.

English discusses zoom eyepieces in some detail, particularly the Baader Hyperion clickstop zoom, which has clickstops at 8, 12, 16, 20 & 24-mm. The 24-mm setting gives 16.7X, and 8-mm gives 50X on the ShortTube 80 telescope. Angular field of view is from 48° (at 24-mm) to 68° (at 8-mm).

Another subject touched upon is cases... some versions of the ShortTube 80 come with hard cases, others with soft-padded bags; likewise mounts. Tripods come bare or with padded bags. You should be able to find suitable hard case with cut-to-fit foam lining. All this is something to consider if you travel with your gear.

The final section of Chapter 11 deals with binoviewers, which as the name suggests, split the light rays coming from the objective into two beams allowing the viewer to use both eyes together. Splitting of the beam reduces the light available to each eye, and there are also other reflections to get the two beam parallel at the users’ eye-spacing, but some observers say they see more because they are using both eyes. The loss of light (>50%) caused by the splitting and collimating reflections is critical at the limit of visibility, but less critical for brighter targets.

Some disadvantages are the mechanical length of the binoviewer may restrict you to the shorter length 1.25-inch diagonal rather than the longer 2-inch accessory, and hence to specific eyepieces. Many examples transmit a bundle of light rays narrower than eyepieces, so they block-off the outer rim of the field of view; this is called vignetting. Naturally, they must be use with a pair of matching eyepieces, thereby increasing the cost; and binoviewers are in themselves an extra cost. There is a cost advantage of using a single Barlow lens in front of the binoviewer to increase magnification, rather than a matching pair of shorter focal length eyepieces behind the accessory.

Chapter 12 (Founding Days) is an account of the development of the ShortTube 80 from its predecessors in the 1980’s to modern times. Many users of the earlier (1980’s) Chinese telescopes regard them as junk, with poor optics and shaky mechanicals. Even reputable brands like Celestron and Meade suffered from the “Halley’s Comet Craze” of 1986, when too many sub-par examples went out to retailers. Tasco produced a small refractor, a 60-mm/f5 unit that also suffered from quality-control issues; apparently the better examples were quite good.

By the 1990’s the Chinese telescopes were getting better; and Tom Geisler (founding president of Orion Telescopes and Binoculars USA) was particularly impressed by an 80-mm/f5 achromatic refractor made by the Chinese firm Synta. Orion marketed these as the ShortTube 80; bundled with the OTA was a 45° correct-image diagonal, two Sirius Plössl eyepieces (10-mm & 25-mm), and a 6X26 correct-image finder. The OTA has a built-in plate with a threaded ¼”-20-tpi hole for mounting purposes (including photographic tripods). An EQ1 equatorial mount was an optional extra.

Soon after, Celestron, Vixen and Konus marketed their own versions. For all four versions, a high- quality 90° star diagonal considerably improved the system; at the cost of changing the correct- image view to left-right reversed, and no longer matching the correct-image finderscope. Later, other companies such as SkyWatcher marketed 80-mm/f5 telescopes, both as OTAs and bundled with accessories that made up functional telescopes. Later still came the Meade EXT 80, described earlier in Chapter 9.

A few other variants are also described in Chapter 13; most will be difficult to source from an Australian outlet

Chapter 13 (Afterword: The Little ‘Scope That Could) is the final one, and deals with the capabilities of the ShortTube 80. Certainly there are better 80-mm telescopes out there, especially the ED doublets (“semi-apochromats”) and triplet apochromats. The various 80-mm/f5 achromats offered adequate performance at an economical price; obviously a winning combination, as reflected in their popularity over a quarter of a century. They were an obvious step up from the typical refractor of earlier years such as the 60-mm/f12 of the 1960’s.

Neil English has an obvious soft spot for his 80-mm/f5, which he values alongside his serious telescopes – high quality Newtonian reflectors.

The Author compares the ShortTube 80 with the small reflector (4.2-inch) that William Herschel made for his sister Caroline to use in her searches for comets. Her low-power eyepiece was 15X according to Caroline, 24X according to William. Her higher-power eyepiece gave her 30X (indicating a low power of 15X rather than 24X). Her discoveries made her famous, suggesting that the ShortTube 80 is can be a serious performer, especially when used by very experienced observers. The Author very aptly quotes William Herschel on the last page of this book: “Seeing is an art.” Also, Charles Messier’s favourite telescope was an 89 mm f/12 chromatic refractor working at 120X; (but English doesn’t mention this).

Finally there is the Index. This is too brief, at only three pages long. Most books would have an Index 6-12 pages long, and at least one entry for each letter, except perhaps Q, V, X & Z. This book has no entries for H, I, O, Q, T, U, W, X, Y & Z. Naturally, there are many entries for M (Messier objects), and N (NGC objects). Some of the Author’s Messier targets have been omitted from the Index (by mistake?): M 16, 41, 43, 48, 55, 57 and 88. There are also omissions of NGC target objects from the Index: NGC 6992, 6995, 6871, 7662, 1907 (with M36, M37, and M38: A Trio of Messier Open Clusters in Auriga), 2383, and 2244 (with NGC 2237-2239, the Rosette Nebula/Calwell 49). One of the Collinder Catalogue targets (Collinder 70) appears in the Index, the other Collinder 399 – The Coathanger, or Brocchi’s Cluster) does not. Two of the Melotte Catalogue targets are also missing from the Index: Melotte 20 and 25. The target Caldwell 14 - the (Glorious) Double Cluster in Perseus is also absent from the Index.

The double star targets of Chapter 8 don’t appear individually in the index, with a few exceptions that are in Chapter 4, such as “Polaris A & B”. Other topics discussed/defined in the text, but absent from the Index include: , “Cheshire Eyepiece”, “Collimation”, “Horsehead Nebula”, “Mounts”, “Seeing” (including Seeing Scales- Antoniadi & Pickering), and “Transparency”.

“Star diagonals” doesn’t get a first order category to itself, it is a sub-category “diagonals” under the first-order category “Stars”. Likewise the practice of “Star hopping” to locate faint targets doesn’t get it own first-order entry; it is the sub-category “hopping”, also under “Stars”. (The Author relies on this technique of star hopping in his instructions to the reader, but it warrants only a minor category in the Index.) Similarly, “Double stars” is a first-order category; but multiple stars get the sub-category “multiple” under the category “Stars”; and variable stars get the sub-category “variables”, also under the category “Stars”.

While there are 33 entries referring to “Achromat”, but the Index doesn’t mention “Chromatic Aberration”. Likewise, there are 32 entries under “Aperture” in the Index, but no references to “Magnification”. Various kinds of solar filters are mentioned in the Index, but the Herschel Wedge is not, even though it receives two paragraphs and a photograph (Fig 6.5) in Chapter 6 Watching the Sun. The term “Mounting” is absent from the Index, even though the subject gets a whole chapter (Chapter 3 Mounting the Short Tube 80).

SUMMARY – This book has a few flaws, which can be mitigated by using it in the right way. To find the targets you will need finder charts, a star atlas, or a list of R A & Dec co-ordinates, which this book doesn’t supply. Also, the glossy pages would stick together after a dewy night at the telescope, so don’t take it out at night. Better still, sit in your favourite armchair, and use it in the daytime to make up an observing list. Then gather together your atlas, finder charts and co-ordinate lists for use at the telescope. Keep in mind that this is intended as a practical book for observers in the Northern Hemisphere; and leaves out much of the southern sky. You will need other resources to fill the sky between ~30° S Dec and the South Celestial Pole.