What to look for in a Christmas telescope

Christmas is coming and with all my blather about "What's Up" perhaps you, or someone in your household is expressing ideas about going out to look at what I have been talking about. But, the ads you see in displays at your local store or in catalogs and magazines are filled with strange terms and numbers you know nothing about.

Well, that is why I am here, to help you out, or at least to give you an idea of what you can do, or what you should avoid.

There are two basic types of telescopes, The refractor is basically a tube with lenses at each end. They come in all sizes and price ranges. The second is the reflector which has a curved mirror at the bottom and a second mirror at the top which reflects the light into the eyepiece. This telescope too comes in all sizes, types, and prices.

Both kinds fulfill the basic function of a telescope which is to; 1) collect and focus light from an object; and 2) magnify the object. In short, to make things look bigger and brighter. The measure of performance for any telescope depends on the diameter of the primary lens at the front or the mirror in the back. The larger the lens or mirror, the more light it can gather and the brighter and sharper the view.

Do not be led astray by the claims on the box or advertisement of any telescope claiming exorbitant magnification such as, "Will magnify 600x," or "Will magnify 800x." Magnification is the function of the eyepiece, not the size of the telescope. In theory, there is no limit to magnification power, there is, however, a limit on useful magnification. It is possible to magnify to such a large extent that the image is useless, which new telescope users soon discover. The greater the magnification, the more blurry the image; eventually, the image becomes so blurry it is useless.

A useful rule of thumb for calculating magnification limit is to take the diameter of the main lens or mirror in inches and multiply it by 50. For example, I use a telescope with an 80mm or (roughly) a three inch primary lens. The maximum useful magnification limit for this telescope is three times 50, or 150 power. Going beyond that will be an exercise in futility.

Another rule of thumb is an expensive telescope on an inexpensive mount is the same as an inexpensive telescope. If you can, check the quality of the mount, or tripod. Look through the telescope and lightly touch the tube. The view should wobble for a few seconds and stop. If it vibrates longer -- or if you have trouble tightening clamps that hold the tube steady -- move on. Using this telescope will be an exercise in frustration.

As for price, do whatever your budget can stand. There are some very inexpensive ones (dare I say cheap) at the dime store with a tempting price. But, there you are getting what you pay for, usually in this case poor optics and a wobbly mount. Expect to pay a minimum of $250 for a basic, no-frills quality small scope. A larger budget will give you more choices, better optics, and larger sizes and/or frills such as motor drives and automatic pointing. Just remember, as Michael Balich of Astronomy magazine said, "The bigger the telescope the better. The smaller the telescope, the more often you will use it."

SKY WATCH: At last, Saturn has returned to the evening sky, if you want to go out at 10 p.m. to look for it that is. Look for the bright star Regulus in the constellation Leo, look for Saturn just above it. New Moon, Dec. 20, and winter begins on Friday, Dec. 21. Probably the best meteor shower of the year, apart from the Perseids of August, will peak on the late evening, early morning hours of Dec. 13-14. The Geminids, appear to come from the constellation Gemini, (a rectangle shaped constellation just north of Orion).

Rates of 100 meteors per hour are possible after midnight in a dark sky place. Two years ago I spent an hour in the late evening and counted 75 per hour -- and this was before the peak viewing time. The Geminids are exciting because there are lots of bright fireballs with the shower.

Dress warm, get a thermos of hot chocolate, a blanket or sleeping bag, and your reclining lawn chair from last summer, go to your dark sky place and enjoy the show. The Moon rises a little after 1 a.m. So try to look before then if possible.

Next time, the Christmas Star.