Choose wisely, and you will spend many hours of enjoyment with your new instrument. Choose poorly and, at best, you will end up with a unique and expensive hat rack.

Today, some telescope makers design three- or four-element lenses to bring the different wavelengths of light to concurrent focus. These are called apochromat refractors. Another option is to make one of the two-element lenses either from a material called calcium fluoride or fluoro-phosphate crystal. These latter telescopes are called, respectively, fluorite or extra-low dispersion (ED) apochromats.

As you might expect, the more elements or specialty glass you use -- not to mention the larger the aperture -- the more the cost. For a 3- to 3.5-inch (80- to 90-millimeter) telescope, the price is not too bad. But employ more glass elements or specialty materials to fashion the lenses and you have a telescope with near-perfect optics -- and worth a small fortune.

Consider that if two elements are used, four lens surfaces must be accurately figured. If you use three elements, that jumps to six, and so on. As for calcium fluoride and fluoro-phosphate, they are more difficult to work with than glass and consequently are more expensive. They can raise the cost of a telescope by as much as $1,000.

Still, you have to balance this with the fact that refractors deliver crisp, high-contrast images at high magnifications, which make them perfect for planetary, lunar and double-star observing. Moreover, today's achromatic refractors render almost color-free images at nearly half the price of the apochromats, fluorite and ED apochromats. Unfortunately, you won't find an affordable refractor in objective diameters over 4 inches (101 millimeters). For a typical 5-inch (127-millimeter) refractor with mount and basic accessories, expect to pay between $3,000 and $4,000.

So maybe the spouse won't let you spend that kind of money, or perhaps little Jimmy doesn't really need a 5-inch refractor to play with. What are your other options?

Despite many advances in telescopes, particularly accessories, which we'll get into in the next section, I think the best all-around telescope for beginners is the Newtonian reflector.

Reflectors are the least costly per inch of aperture to manufacture (only one optical surface to figure), they are adaptable to various designs and uses and, because light does not have to pass through glass, they provide color-free images.

Alas, the reflector's greatest strength is also its greatest weakness. The primary mirror is ground to a concave figure known as a paraboloid. The outer zones of such a mirror have a slightly longer focal length than the inner zones, particularly for telescopes with short focal lengths (their mirrors must be ground to a deeper concave figure, which only exacerbates the problem).

Hence, star images near the edge of the field of view look as if they have short cometary tails or "wings." This aberration is called coma.

Reputable telescope manufactures do their best to minimize coma, but it's an inherent design flaw that cannot be completely eliminated. Most commercial telescopes 10 inches (25.5 centimeters) and larger are made with short focal ratios -- f/4.5. They gather a lot of light and provide stunning views of deep-sky objects, but you have to accept a little coma at the edge of the field. Still, as long as the image in the center is sharp, who cares about the edge?

The most popular reflector for beginners is either a 6- or 8-inch (15- or 20-centimeter) Newtonian utilizing a Dobsonian mount design. ("Dobsonian" refers to telescope maker John Dobson who, in the 1970s, came up with a simple design whereby the tube moves up and down in altitude and pivots around a central axis in azimuth, much like an artillery mount.) A good 6-inch "Dob" goes anywhere from $250 to $400. Imagine how much a refractor of similar size would cost?

There is one final hitch with owning a reflector. The mirrors, particularly the primary mirror, often come out of alignment, particularly if the telescope is regularly portaged from one place to another. The user must then "collimate" the optical components so they square up. The process is not complicated, but some people prefer not to be bothered. Given the optical advantages, performance and affordability of reflectors, collimation is a minor inconvenience.

Never mind the name. All you need to know is that the term refers to an optical system involving both the refraction and reflection of light. The most popular member of the catadioptric family is the Schmidt-Cassegrain telescope, or SCT.

SCTs are portable, compact and not as pricey as refractors (though they are still pricier than reflectors). More importantly, the combination of mirror and front corrector lens ensures colorless rendition of objects and sharp focus across the field of view. Because the light path of an SCT is "folded" inside the tube, you end up with a long focal-length telescope that is only twice as long as it is wide. This, in turn, yields large image scales, which are best for viewing the moon, planets and double stars, as well as small, bright deep-sky objects.

Devotees argue that SCTs really shine as astrophotographic telescopes. Indeed, they are easily adaptable for photography and digital imaging. Eyepiece placement at the rear of the telescope allows you to easily attach cameras and accessories, and their fork mounts are especially smooth when automatically tracking celestial objects. In fact, many models are now equipped with computer-driven mounts that do everything except set the telescope up for you. (More on that in the next section.)

But SCTs also have their limitations. For one thing, in sizes over 8-inches, they are expensive -- and adding in the necessary accessories drives up the price even more. If you want to get into serious deep-sky observing, you'll need at least an 11-inch (28 centimeter). Your basic cost will be around $3,500.

By design, SCT telescopes also have large secondary mirrors, which are usually about one-third the aperture's diameter. This results in scattered light and a slight loss of contrast. Their exposed corrector lenses are especially susceptible to dew (unless shielded), and the secondary mirrors often need re-collimating. Finally, at focal lengths of f/10 or greater, even a low-power eyepiece produces a limited field of view. If you want to look at or photograph star fields and large deep-sky objects, you will need to purchase yet another accessory -- the focal reducer. These can convert an f/10 system to f/6.

SCTs offer the advantages of both refractors and reflectors, while creating a new set of disadvantages that you either may or may not be able to live with. For astrophotography and electronic imaging, however, SCTs reign supreme.

Also in the catadioptric class are "hybrids," like Newtonian reflectors fitted with special corrector lenses. These are called Maksutov-Newtonians.

A similar arrangement with Cassegrain telescopes yields a Maksutov-Cassegrain. The type of corrector lens used on these instruments is easier to manufacture than the SCT and yet they provide coma- and color-free images that are sharp across the field of view. Expect to pay somewhere between what an SCT and a large Newtonian costs, but also expect near-perfect optics for your money. (Okay, I admit it. I own a Mak-Newt and love it.)

All telescopes have the same mission -- to gather and magnify light from distant objects, but they do it in different ways. And while no telescope is perfect in design or manufacture, there is a very likely a telescope out there that is perfect for you.