Eventually, there will come that time when you'll want to purchase a telescope. But what type of telescope should you choose? There are three types to consider:

• A refracting telescope has a convex objective lens at one end and an eyepiece at the other.
• A reflecting telescope uses a concave mirror instead of an objective lens. This mirror (called the primary) sends light up through the tube to a small flat mirror (called the secondary) which intercepts it and sends it to the eyepiece on the side of the tube.
• A catadioptic telescope is a special type of reflecting telescope that possesses a correcting lens on top to form the image. Most catadioptics are of the Schmidt-Cassegrain design. Light passes through the corrector, reflects off the primary, then off a curved secondary, and finally passes through a hole in the main mirror to reach the eyepiece.

Unfortunately, space is far too limited here to discuss all the telescopes you could purchase. The best advice is to keep it simple!

If you're just starting out, you might want to consider a 2.4- or 3-inch refractor or a 4- or 6-inch reflector. Make sure that the telescope can be set up quickly, but that it still has a sturdy mount. Even a good telescope is virtually useless if it's mounted on a shaky or wobbly tripod.

Don't fall into the trap of purchasing what some amateurs refer to as a "trash telescope." Basically, a trash telescope is one that, along with having a poor mount, has been advertised by the manufacturer as promising "spectacular views" of the moon or the rings of Saturn at magnifications of, say, 500-power or more. Unfortunately, too many uninitiated amateurs are "power happy." Any telescope will provide you with high magnification, which not only increases the size of the image but also increases the effect of viewing an object through our turbulent atmosphere. A high-power image, especially with a small telescope, will often turn out quite dim and blurry. For the amount of money you might spend on such an instrument, you'd be better off investing in a pair of good binoculars.

A rule of thumb: The maximum amount of magnification for any telescope is 50-power per inch of aperture. So if you intend to buy a 6-inch reflector, 300-power is as high as you should ever attempt to go; the maximum for a 3-inch refractor should be 150-power. In fact, you'll probably be surprised to discover that your most pleasing views will come at much lower powers.

Sometimes, however, people get into trouble when purchasing even a quality instrument. These folks go right out and purchase a very expensive telescope, bring it home, try setting it up, and in the process get completely confused. So don't waste your money or your time: Learn the sky, get some binoculars, see how much the hobby consumes you, and then make an intelligent telescope purchase.