Friday, 17 February 2012


By David Knisely

Learning the constellations and the apperance of the sky at various times of the year is a useful and fun way to get familiar with where things are in the heavens, and a good guide book plus a planisphere will definitely help with this task. However, once you begin a telescopic search for the many deep-sky objects scattered about the numerous stars of the major constellations, you really need a good detailed "road map" of the sky to keep from getting lost, and a star atlas is just that. An atlas is useful, not only for helping with the finding process, but as an aid in planning future observing sessions. There are a number of good atlases in print today, and below are some of ones most commonly used by amateur astronomers.
NORTON'S 2000.0 STAR ATLAS AND REFERENCE HANDBOOK, edited by Ian Ridpath (Longman Scientific & Technical, 1989) is considered to be one of the better basic observing guides for the amateur. This updated version is the 18th edition of a classic work which has been helping observers since it was first published in 1910. In addition to containing useful all-sky star charts, the book is an excellent reference handbook for the amateur astronomer. The atlas portion of this hardbound book contains sixteen 8" by 11" star charts covering the entire sky, ploting 8,700 stars down to magnitude 6.49 (most of the "naked-eye" stars), along with 600 of the best deep-sky objects. The stars are plotted as black dots of varying size on a white background, which makes for easier reading in dim light. The charts also show the brighter parts of the Milky-Way (green), as well as showing the coordinate lines, extensive object labeling, and constellation boundaries.
The 16 maps are laid out in adjoining form, so by opening the book flat, you get a really wide continuous area of coverage on the sky. Since the charts are bound in book-form, objects near the binding line (where adjoining maps meet with no overlap) tend to be a little hard to see unless the book is really pressed open, but othewise, the maps are very useful for the beginning to intermediate amateur.
In addition to star maps, the book also contains 4 detailed quadrant maps of the near side of the Moon, and a small map of the albedo features on Mars. Norton's also is a real goldmine of useful information for the amateur astronomer, covering things like practical astronomy, time, telescopes, viewing solar system objects, and the stars in general.
TIRION'S BRIGHT STAR ATLAS 2000.0 by Wil Tirion (32 pages). This is a bound set of ten 9" by 12" star maps of the entire sky, showing 9,096 stars down to magnitude 6.5, along with 600 of the best deep-sky objects. Again, the stars are plotted as dark dots on a white background for easy reading in dim light. Like its "big-brother" (Sky Atlas 2000.0), it has celestial coordinate lines, Milky-Way and constellation boundaries, and extensive labeling. It also contains a set of 6 seasonal constellation finder charts. It is a useful and inexpensive atlas for the beginner who is starting to "go deep", but for best results, the user should also have a good companion reference like Burnham's Celestial Handbook, or Deep-Sky Observing With Small Telescopes, by David J. Eicher.
SKY ATLAS 2000.0 by Wil Tirion (Sky Publishing), has become one of the true "standard" star atlases for intermediate and advanced amateur astronomers. The sheer number of objects shown make it a must-have for those who are doing deep-sky searches like those involved in the Messier and Herschel programs. Sky Atlas 2000.0 plots the positions of 43,000 stars down to magnitude 8.0, along with 2,500 deep-sky objects, on 26 large 18" by 13.5" charts covering the entire sky. The scale of the charts is somewhat larger than that of other atlases, which makes locating things in crowded fields easier. Objects like open and globular clusters, diffuse emission or reflection nebulae, planetary nebulae, and galaxies are all plotted with different symbols and are all labled clearly (in color for the Deluxe version). Double, multiple, and variable stars are all shown, along with the large-scale coordinate grids and constellation outlines. Clear plastic overlays are provided to assist in determining the coordinates of any celestial object, or in locating objects which are not plotted, but whose numerical positions are known. An all-sky wide-field constellation finder chart with map boundaries and page numbers is provided at the beginning of the atlas to assist with locating the map of interest. The atlas comes in five versions:
1. Field Edition (unbound single-page charts with white stars and markings on a black background).
2. Desk Edition (unbound single-page charts with black stars and markings on a white background).
3. Laminated Field Edition (spiral bound, and encased in clear plastic).
4. Laminated Desk Edition (spiral bound, encased in clear plastic)
5. Deluxe Edition (spiral bound with Lexan cover, with charts which fold out to 20" by 15.5": black stars and markings on white background with colored symbols for deep-sky objects and Milky Way outlines.
Sky Atlas 2000.0 is somewhat more expensive than the other two atlases mentioned earlier, but it does plot more objects on a greater scale, and tends to be more useful to the serious observer. Again, for best results, a good advanced observing guide is needed. Several catalogs for objects plotted on Sky Atlas 2000.0 are available, such as the Sky Atlas 2000.0 COMPANION: a complete listing of every deep sky object plotted on the atlas. A more complete 2-volume catalog SKY CATALOGUE 2000.0 is also available, but, like Sky Atlas 2000.0 Companion, it is not an observing guide.
URANOMETRIA 2000.0, (Wil Tirion, Barry Rappaport, George Lovi, published by Willman Bell) is a highly detailed two-volume hardbound atlas intended for use mainly by advanced amateur astronomers. This atlas is indispensable for the large telescope user intent on pushing towards the limits of Deep-Sky observing. It plots 332,000 stars as faint as magnitude 9.5, along with an incredible 10,300 non-stellar objects (open and globular clusters, bright and dark nebulae, galaxies, radio sources, quasars, ect.) on a total of 473 individual charts covering the entire sky. The stars, object symbols, and coordinate grids are plotted as black on a white background page. Some of the common object names (ie: "Horsehead Nebula", ect.) are also printed next to certain objects. The scale of these charts is much larger than for Sky Atlas 2000.0, with only portions of larger constellations being shown by any one page (13 degrees of declination shown per page). Unlike other atlases, adjoining pages do not together form a contiguous left-to-right area of sky (pages are in order of increasing right ascension). This, along with the large scale and huge number of stars and other objects plotted, makes the atlas more difficult for the inexperienced observer to use. It is definitely NOT for beginners, as they could quickly become totally lost in its pages.
Uranometria does contain wide-field guide charts in a polar projection to help the user locate the page containing the smaller area of interest, along with plastic overlays for the main charts for fine coordinate measurement or object location. Its 2 volume hardbound-only edition is more expensive than Sky Atlas 2000.0, but it is definitely worth the money for the advanced amateur who has outgrown the other atlases. There is also a companion catalogue, THE DEEP-SKY FIELD GUIDE TO URANOMETRIA 2000.0, which has a great deal of data covering every non-stellar object plotted in the atlas.

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