Every year the choice of books, equipment and software for astronomers grows more dizzying.
If you are shopping for yourself you should have a pretty good idea of what you want. For a probably non-astronomical friend or relative the issue can become really difficult. If your family astronomer is an experienced one, he or she should know what Santa should drop off at Christmas, and be considerate enough to drop a few hints. Listen hard for them. However, if you are encouraging a beginner, things get more complicated. Good choices can start a lifetime of discovery and enjoyment. I hope this article is of some help.
All backyard astronomers need a planisphere. This consists of two plastic discs with a rivet through the middle, so that one can rotate over the other. The lower disc has a star map on it and a calendar around the edge. The top disc has a window in it and local standard time around the edge. Set the time on the date and the window will show the constellations in that sky at that time. Get the plastic model, not the cardboard one, and select the one for your latitude. Add to this a copy of the Observer's Handbook, published each year by the Royal Astronomical Society of Canada. This provides information on eclipses and other astronomical events, when and what planets are visible in the sky, and a wealth of other astronomical data. This book is invaluable.
Our minds naturally turn to telescopes as presents for astronomers. However, this is a potential disaster area. Many department stores offer impressive looking instruments, offering incredible magnifications at affordable prices. In almost all cases these gadgets are useless, in fact non-functional. Moreover the people selling them know little about them. One local store had one of these telescopes on display. It had been rendered even more useless by having been wrongly assembled. For good advice on telescopes and binoculars, along with a lot of other useful material, Terence Dickensonís book Nightwatch remains a good source. You can use it for advice in choosing the other presents and then make it an additional gift.
Your family astronomer's first telescope should be good binoculars. A pair of 7x50's (seven times magnification with 50mm diameter objective lenses) would be a good start. These are great for astronomy and also wildlife viewing. Get the best ones you can afford and try them out first. Binoculars consist of two telescopes, fitted together so they are looking in exactly the same direction. Many cheap binoculars have the two telescopes not lined up properly. Your brain can correct for this at the expense of discomfort and eventually a headache. It should be possible right from the start to adjust binoculars so they are completely comfortable to use.
A telescope for a beginner should be easy to use. If it is intended for a small family astronomer, size and weight are an issue. Get a small refractor telescope (the traditional telescope with a lens at each end). It should have an objective lens with a diameter of at least 50mm. Astronomical objects are faint, and the larger the objective lens, the more light it collects and the brighter the image. Eyepieces need to be interchangeable, to suit different kinds of observation, so make sure the telescope uses standard eyepiece sizes: 1.25 or 2 inches.
Lastly, good, firm tripod is essential. If possible, do your shopping at the local science store, face-to-face with an expert. Otherwise there are telescope dealers on the web, in which case it would be a good idea to contact the local astronomy club for advice. A membership in that club might be a nice, additional present. Sharing a hobby with others helps it grow and increases the enjoyment. Merry Christmas!
Venus shines brilliantly in the predawn sky, like a searchlight, with Jupiter above it and almost as bright. Mars, much fainter, lies between them. The Moon will be New on the 11th.
Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, Penticton.