Finding the perfect Christmas gift for the astronomer in your life

December Sky Chart.

Barry Malpas

December Sky Chart.

Astronomy is one of the few sciences with which anyone can get involved at a variety of levels. Maybe your fifth grader has gotten the astronomy bug at school. Or maybe you just retired, want something to do, and noticed that we in northern Arizona have a pretty interesting sky that people around the country would die for. Wouldn’t a telescope make a great present for the holidays?

But what do you need and where do you start?

Telescopes can be expensive. Well, here is a little background, a few pointers and suggestions to ease you into this enjoyable and educational avocation, along with a final recommendation.

There are basically two flavors of telescope, refractors and reflectors. The former uses lenses to magnify the image, while the latter uses a large mirror. In either case, you can easily spend several thousand dollars with all the automatic “go-to” mounts, and special doodads available on the market. You can also spend very little at a large box store and get basically junk which, will leave you frustrat-ed.

So, the first rule of thumb is: Stay away from Walmart, K-Mart, toy stores, or even most camera stores. What they sell is usually worthless, and most likely, no one there knows telescopes. Rule two is: Go for the basics. There are two things about astronomical op-tics you need to know. Although magnification is important, light gathering power is more-so. The larger the primary objective (main lens or mirror), the more light can be collected by the telescope. It’s a math thing, where twice the objective size gets you four times the image brightness and clarity. So, in an effort to get more bang-for-the-buck, I automatically rule out refractors. Why? Because they are more expensive to make, and will cost several times the price for the same aperture reflector.

Now, there are also several types of reflectors. Newtonian and Cassegrain are the two most common. The Newtonian is simple in de-sign with just two optical parts involved, and they are relatively inexpensive. But I have left out one thing … the mount. There are two types of mounts: equatorial and alt-azimuth. Again equatorials are very useful because they can track objects in the sky as the Earth turns. But they are also costly. The most useful and easily portable mounts are the Dobsonian alt-azimuths. They are easy to use and transport. Though they don’t find objects for you or track them, for the lesser cost of a Newtonian with a Dobsonian mount, you will become much more familiar with the night sky.

Another important factor to consider is magnification. Changing the power is done by using different eyepieces in the telescope. A shorter focal length eyepiece will yield a higher magnification. Most telescopes come with just one eyepiece (25mm), and since different objects will require different magnifications, you will want to purchase a basic set. There are several sets that come in protective cases and contain excellent optics (along with filters) at reasonable prices, especially for the beginner. Orion, Celestron, Meade and Zhumell each make excellent eyepiece kits for about $140-170, and Orion makes an even more basic one for $80. One thing to remember is that some companies include eyepieces that you may never use. Each kit has a Barlow lens which doubles the magnification of each eye-piece. But the limit of the magnification of any telescope is about 40 times the objective diameter in inches. Any higher magnification makes things fuzzy. So, a 6-inch scopes maximum usable magnification is 240x, yet a 4mm eyepiece will yield about 300x, quite a bit be-yond the telescope’s limit. Another situation is duplication. If 18mm and 9mm eyepieces are supplied with a 2x Barlow (that comes with each kit), the 18mm and Barlow is equal to the 9mm. The best sets of eyepieces will be staggered, so if there are three eyepieces, the Barlow will give you a maximum of six magnifications.

My pick for the best basic telescope that will keep you interested in viewing at a reasonable cost (which I have also recommended to school astronomy classes here in northern Arizona). The 8-inch Orion Sky Quest Newtonian-Dobsonian ($380) with their more basic eyepiece set ($80) which affords six different magnifications from 48x to 320x. Also, if you want to take some photographs, the moon is an interesting and bright object that can be easily imaged using most cell-phone cameras held up to the 25mm eyepiece of a telescope.

The two best resource publications to consider “NightWatch: A Practical Guide to Viewing the Universe,” by Terence Dickinson, which covers the most interesting objects to observe in the sky and how to locate them, and includes very useful star charts ($35); and “New Atlas of the Moon”, by Serge Brunier and Thierry Legault, a comprehensively illustrated book with overlays which examines the moon in intricate detail allowing the amateur to easily locate hundreds of lunar features ($30).

The Coconino Astronomical Society at www.coconinoastro.org is also a valuable resource.

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