A good star atlas is essential for finding your way around the night sky and locating interesting objects. This is especially true in washed-out skies, where you may not see enough stars to easily recognize all the constellations. But which star atlas is right for you? In this first of a series of atlas reviews, I’ll look at Sky & Telescope’s Pocket Sky Atlas. This is a beautifully printed atlas designed specifically for use in the field. Its spiral binding and compact format make it easy to use at the telescope. It’s also a good match for washed-out astronomers to use for star-hopping because its magnitude limit for stars corresponds well to what you can see using finder scopes and binoculars in light-polluted skies, and the deep sky objects included cover just about anything you can hope to see with a telescope from urban areas. On the other hand, if you are looking for something to help you learn the constellations and generally find your way around the night sky, the Pocket Sky Atlas may be the wrong tool: the charts are too narrow and too detailed for that. To make effective use of this atlas you should already be able to locate the major constellations. Allow me to explain further...

General Description

The Pocket Sky Atlas is published as a 6” x 9” spiral-bound book, which makes it easy to fold back and hold at the telescope or to lay flat on a table or stool. The scale provides a good balance between too small a scale (meaning the individual charts cover too small a region, forcing excessive flipping from chart-to-chart as you star-hop) and too large a scale (meaning stars and objects are crowded together, making it hard to read). Stars are printed in black on a white background. Deep sky objects are shown in color, with both color and shapes/icons used to distinguish between the various kinds of deep sky objects (open clusters, globular clusters, galaxies, planetary nebulae, etc.). The Milky Way is shown with two tones of light blue shading. Variable stars and double stars are also indicated directly on the charts. A handful more exotic objects, such as quasar 3C 273 and Barnard’s Star are also marked, even though the atlas is insufficiently detailed to locate these objects reliably.

Objects are clearly labeled. Messier objects are marked using M numbers; the remaining objects are marked using their NGC numbers if they have them, or if not other appropriate catalog designators. All the Caldwell objects appear in the charts, but are not labeled with Caldwell numbers; there is an appendix that translates Caldwell numbers into NGC numbers along with the chart(s) they appear on. All of the Herschel 400 objects are plotted, even if some of them are fainter than the magnitude cut-offs. Common name labels also appear for all of the well known objects (e.g., Saturn Nebula, Kemble’s Cascade, Blinking Planetary).

To give you a taste of how the Pocket Sky Atlas looks, here is a photograph of a full-page spread from the Pocket Sky Atlas, as well as a close-up of the region around M27 (click on the images to see higher resolution versions). In the future I’ll provide close ups of this same region from other atlases to help you better compare them. You can also download a sample page [2].

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By the Numbers

The basic information about the Pocket Sky Atlas appears in the following table:

Pros

Overall this the Pocket Sky Atlas a very useful atlas. The following features are particularly worth highlighting:

• The star limit of magnitude 7.6 corresponds well to what finder scopes or general purpose binoculars will show you under washed-out skies. You will probably see more stars than the atlas shows, but not so many more that you are likely to be confused.
• The deep sky objects plotted include just about all the objects you can hope to see under washed-out skies, plus plenty more that you can see if you get to a dark sky location.
• Size and orientation are shown for the larger galaxies, nebulae, and clusters.
• Markers at the edges of the charts indicate the adjoining chart, making it easy to find the “next page”.
• The spiral binding and sturdy paper make it stand up well to repeated use in the field. It stays open wherever you leave it.
• The front flap has a convenient scale and telrad circles that you can see from any of the left-hand chart pages.
• The fonts are easy to read, and show up well under red-light.
• The charts are grouped by Right Ascension, which means that the charts for a particular season are all close to each other.
• It includes four detailed charts with zoomed in views of the Orion Nebula region, the Pleiades, the Virgo cluster, and the Large Magellanic Cloud.
• Over four dozen carbon stars are marked.
• The index lists all the objects by type, and includes cross-references for Messier and Caldwell objects.

Cons

No atlas is perfect. The Pocket Sky Atlas falls short in the following ways:

• The “wedges” or “slices” into which the atlas is divided are arranged in order of increasing Right Ascension, which means that charts that graphically appear to the “right” (meaning “west”) of the current chart actually appear before (instead of after) it. This counter-intuitive behavior is common to many atlases and I wish they would order star charts in order of decreasing RA to make the page flipping more natural.
• The star limit of magnitude 7.6 is not enough for star hopping from dark sky locations.
• The use of red for galaxies can make them hard to see when using a red-light.
• Although the pages are made of heavy weight paper with a smooth finish, they still get damp when conditions are dewy. While the pages dry out well, after a dozen or so times they start looking a bit beat up.

Also note that while the Pocket Sky Atlas has an index, it does not have a corresponding catalog. You must use some other source to identify the various objects and their properties (magnitude, size, etc). This is not really a complaint, as including any kind of catalog would have made the Pocket Sky Atlas too big. These days you can easily look up information about any object on the web. But it would be nice to have a catalog as an optional companion volume, as Sky Atlas 2000.0 does.

Summary

The Pocket Sky Atlas is great match for urban and suburban astronomers. It is conveniently sized and well designed for use at the telescope. The charts are tailor made for use in washed-out skies, showing the right number of stars for star hopping in light polluted skies and essentially all the objects you can hope to see. Although it doesn’t go deep enough for finding the fainter fuzzies from dark sky sites, it is still adequate for finding hundreds of interesting objects whenever you do escape to a dark location. This atlas stands up reasonably well to regular use in the field. Best of all, you can buy it for under $20 at Amazon. At that price, there is little risk in buying a copy and you can even afford to replace it every few years if it gets too beat up in the field.

Sky & Telescope’s Pocket Sky Atlas
by Roger W. Sinnott
Publisher: Sky Publishing
Number Of Pages: 110
Publication Date: 2006-03-30
ISBN-10 / ASIN: 1931559317
ISBN-13 / EAN: 9781931559317