Telescope Buyers' Guide

Does the beginning astronomer need a telescope to begin exploring the night sky? Not at all—a handy star chart and the naked eye can pick out constellations and a decent pair of field glasses will bring the junior astronomer’s first subject, the moon, into sharp focus. For more detail, and to extend the vision, however, a telescope is the next step.

Ask Yourself a Few Questions About Telescopes

First of all, why do you want a telescope? What do you want out of it? If your interest is a casual one, then you can make do with an inexpensive, lightweight scope with a large field of view, or even a good pair of binoculars. If you are more serious about astronomy, however, and are willing to spend a little (or sometimes a lot) more, then there are a wide range of options available to you.

The main function of a telescope is to gather light; thus, the aperture of the scope is the most important feature. This is the part of the telescope that allows light to enter. The telescope’s “objective” is also important—this is the lens or mirror that gathers the light. The wider the surface area of the objective’s aperture, the more light it can gather, and the fainter the stars you will be able to see.

The more light that is gathered, the sharper the image you will see. A sharper image means more detail, which is what you want. Also important is the focal length; the longer the telescope, the larger the image will be.

Types of Telescopes

The basic telescope, and the one most likely to be found in a toy store, is the Refractor Telescope. This is also the first kind of telescope ever built, and uses a lens to gather and focus light. There are a few advantages to this kind of telescope (including cost) that make it a great starter scope, and one that can serve the amateur astronomer well for a very long time.

The other kind of telescope, the kind most often used in observatories and more advanced amateur scopes, is the Reflector Telescope. This scope uses a mirror to reflect and focus light, and because of the angle at which the light enters the atmosphere, does a better job of it than a refractor scope. Some of the disadvantages of a reflector scope include constant realignment and cleaning.

The Practical Limit of Power

When shopping for a telescope there are bright and shiny things to distract the consumer, and they are not stars. These are the advertiser’s claims of high power that, in practical application, are useless and worse than useless to the consumer. There is no theoretical limit on power, but there certainly is a practical one. Some objects in the night sky can only be seen clearly at low power settings. A power of 50 times the diameter of the main lens or mirror is the highest for practical purposes that a consumer can use. A power advertised into the hundreds will be overkill.

Final Thoughts

Jumping right into an expensive, massive, reflective telescope may not be the best move for the beginning astronomer. Beware the lure of too much power; up to 50X is good for wide views, such as galaxies and nebulae, 100X for the rings of Saturn, and up to 200X for the surface of Mars.

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