As we approach the holidays that cluster around the winter solstice, people ask me about choosing a telescope for a gift.
The bad news is that there is no nickel cigar or telescope. The fabrication of optical surfaces to a precision of a millionth of an inch is not trivial, and the proper mounting of the lenses or mirrors into a user-friendly telescope is not cheap. The $50 to $100 telescopes at the big box stores are a path to disappointment, and they are destined for a lifetime of storage in a closet or basement.
Such telescopes can give pleasing views of the moon and the bright planets, but finding faint objects will be difficult if not impossible. Most of these have simple “alt-az” (altazimuth ) mounts that point in an up-down and right-left manner, cheap to build but incompatible with the angled rising and setting of celestial objects as viewed from anywhere on Earth but Santa’s backyard or at the South Pole. Finding interesting objects is the main problem.
The two-part solution begins by tilting one of the mount’s axles parallel to the Earth’s rotation axis – the so-called “equatorial” mount. The higher-end cheapies have equatorial mounts and often a motor on that tilted axis to follow celestial objects as they are rising or setting. They may add some dials to read the position of the view, but interpreting those coordinates may require that you have at least a minor in math.
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The key part of the solution is to add a built-in computer that knows how to do that math. These “smart” telescopes have GPS, so they know where they are on the Earth, as well as the date and time. You point them to a couple of bright, recognizable stars and tell the telescope what those stars are, and then it knows how it is aligned to the compass and the sky. The rest of the problem is just calculations – and it knows how to do those. You then select from a list of hundreds of targets in its controller’s menu and the scope goes to target.
Such capabilities come at a price, starting around $400 for about a 4- to 5-inch diameter model, at least in one of the dependable major brands such as Celestron or Meade. If you are not willing to start at that price, then it would be best to choose a good pair of binoculars for a first investigation of the night sky. If that piques your interest, then the next step is one of those smart telescopes. If not, at least you have a pair of binoculars for other activities.
Happy holidays, and happy sky viewing!
Daniel B. Caton is a physics and astronomy professor and director of observatories at Appalachian State University. Email: firstname.lastname@example.org. More on this month’s column: www.upintheair.info.