Posts Tagged atlas

Pocket Sky Atlas

Just buy it.

Seriously. Just buy it. Are you just getting into astronomy? Can’t actually buy a telescope yet but interested in learning about constellations and the various objects you’ll be able to see when you do get one? Just buy this. Been observing for a while but don’t have a nice handy little reference to take with you for short sessions at the telescope? Buy this.

We own two, because we each need one when observing. (And we’re bad at sharing.)

Halfway between A5 and A4 in size, and spiral-bound, this is immediately an appealing book. The blurb describes it as fitting into the glove box, which is a good way of selling it. It’s not quite a genuine pocket-book, but compared to most atlases it’s a treat. It has slightly waxy pages which means they don’t mind a bit of dew, too, which is marvellous when observing in damp conditions.

The book opens with a very brief introduction, explaining the origins of the atlas – in the search for convenience – and what it actually shows – stars down to about mag 7.6; doubles, variables, galaxies brighter than 11.5, globular clusters brighter than 10.5, planetary nebulae brighter than 12. It also explains the labels used, how the charts are arranged, and includes a select bibliography which can be used for those wanting something than goes further (or just a good collection…).

The charts are arranged in order of Right Ascension, in sets of ten. It begins with RA 0-3, and the introductory page (a similar one appears at the head of each ten) explains in which months this part of the sky is high in the evening, at midnight, and in the morning (in this case, Nov and Dec; Oct; Aug and Sept). It also has a map, repeated in many places, of the entire sky, with major constellations and the maps on which they appear; the section under specific consideration is shown in bold. Turn the page and, before getting to the maps themselves, there is a key to understanding the maps: how to identify galaxies, nebulae, clusters, and stellar magnitudes.

The maps themselves are quite detailed, with lines connecting the stars of a constellation in green, galaxies in red and other non-stellar objects mostly in yellow. Each map has arrows and labels showing which other maps it connects to (there is good overlap), and RA and Dec are easy to follow. There are four detailed maps: of the Pleiades, of Orion’s Sword, the Virgo Galaxy Cluster, and the Large Magellanic Cloud.

One of the most useful aspects of this map is that the front cover is not part of the spiral binding, meaning that when the book is laid open the front cover juts out beyond the page. On this jutting-out section there are three things: a ruler indicating angular distance on the charts (up to 15 degrees); the scale for determining star magnitude from -1 to 7 (because as usual this is indicated by relative size on the map); and a red Telrad finder with circles at 2 and 4 degrees. For quick referencing while observing, this inclusion is invaluable.

The book closes with several indices. It has a list of bright stars, by name; a list of galaxies by NGC and IC reference, as well as name; open clusters; globular clusters; bright and dark nebulae; and planetary nebulae. All of these, listed separately, also have a reminder of the legend used to indicate them on the maps. Lastly, the book includes objects in the Caldwell Catalogue and the Messier Catalogue. Excellent for those of us who like lists and/or challenges, or who are feeling lazy when it comes to planning an observing run.

Would I buy it again? I already mentioned that we own two, so: absolutely. It’s invaluable.

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Double Star Atlas

When I announced that I might be interested in checking out double stars, James bought The Cambridge Double Star Atlas, by James Mullaney and Wil Tirion, for me. It’s a big book – larger than A4 – although only 148 pages long. It’s spiral bound, meaning that despite its size it’s quite useable: you’re not forced to to deal with an A3 map on your lap while at the eye piece. The paper seems to be good quality and slightly waxy; I’ve had mine sitting on dewy grass and although some of the pages have slight ripples in them now, the book itself hasn’t suffered at all. And it’s got wonderful content, with an excellent introduction and superb maps.

In the introduction, Mullaney takes the reader – anyone from a novice to expert – through the process of making the book itself, then tabulates the codes that are used to signal the discoverer and/or catalogue used when discussing individuals pairs/systems. There is an excellent section on the practicalities of observing – useful not just for doubles hunting – explaining how to train the eye to observe, as well as the impact of sky conditions and the resolution and magnification of telescopes. He also discusses the idea of record-keeping, and it was from reading this that I decided to keep a journal of my observations.

Before getting to the maps, Mullaney has a list of 133 ‘showpiece’ double and multiple stars. As well as giving the name of the object, its coordinates and magnitude, he includes a short and usually evocative description of each object. For those of us who like lists, this is something akin to having a Messier list for double/multiples. It’s a fabulous challenge (although disappointingly for me a fair number are beyond my viewing range, here at 37 degrees south).

The heart of the book is the 30 double-page maps that cover the entire sky (p1 is the North Celestial Pole, p30 the South). The maps show about 900 non-stellar objects as well as the doubles, so it can make an excellent all-round atlas too. The stars making up constellations are connected by faint blue lines, and the ‘spheres of influence’ of the constellations is also shown, which is useful when trying to locate specific objects. The doubles that are specifically listed objects (all 25,000 of them) are labelled in green, making them easier to read under red light. I’ve never been especially good with maps, but these are easy to read and easy to use, both while planning an observation session and while at the telescope.

Finally, there are the Appendices. App A lists the constellations and which pages they appear on; B has the ever-useful table of Greek letters. But C is where the money really is: a list, in order of RA, of the doubles Mullaney specified be in the Atlas. The table has the object’s designation, RA and Dec, magnitude, and the pair’s separation, as well as occasional helpful remarks (this is Antares, this is in the middle of the Pleiades). This appendix can be used to give the astronomer a better idea of exactly what she is looking at on the map; when used in conjunction with an Argo, if a random double is spotted it can be looked up via the RA/Dec to see whether it is listed and if so its name.

Would I buy this Atlas again (or get James to buy it)? In a heartbeat. Of immense value to anyone who is interested in looking at double stars. It’s easy to use, lovely to flick through when planning, and sturdy into the bargain.

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