The Lake County Astronomical Society

Buying Your First Telescope

Jack Kramer

If you're interested in astronomy, you no doubt are considering the purchase of some sort of optical instrument to help you see more of the objects in the night sky. For the newcomer to this hobby, a good pair of 8x50 binoculars is the ideal means to learn your way around the sky. (In binoculars, the "8" in this case refers to the magnification - 8 power - and the "50" refers to the diameter of the large lenses in millimeters.) Binoculars give a wide field of view so that it's easy to locate the brighter planets, star clusters, galaxies, and nebulas. If you're now thinking about getting a telescope, we've put together the following guidelines to help you get something that you can actually use.

1. Telescopes are not cheap - Expect to spend at least $250.00 for a new telescope. Anything substantially less than that is an inferior instrument that will prove very frustrating to use. In fact, some of the cheaper telescopes use plastic lenses, instead of optical glass. Good telescopes are precise pieces of scientific equipment.

2. Forget about magnification - For astronomical work, the maximum usable magnification is 50 power per inch of aperture. That means in the case of a 60mm (2.4") refracting telescope, you should use no more than about 120x. Don't be misled by advertising that claims this size scope gives 300x or more; the image will be fuzzy and the field of view will be so narrow that you won't be able to see anything.

3. The mounting is as important as the telescope itself - If the mount is unstable, you won't be able to keep objects in the field of view. Also, moving from one object to another will be very jerky, so finding anything will be a nightmare! Your best bet is the type of mounting referred-to as an "equatorial". These are generally much more stable and smoother in operation than the "altazimuth" type. If you currently have an otherwise good telescope that's on one of these poor-quality mountings, you can improve the situation by re-mounting the telescope on a good camera tripod.

4. The more metal, the better - Check out the telescope to see how many parts are made of metal. One example is the apparatus used for focusing. Metal parts are more durable and operate more smoothly than plastic parts. This is a good indicator of quality.

5. Purchase from an optical goods store - If possible, buy the scope from a camera store or other establishment that specializes in scientific instruments. They generally know their products and stand behind them.

6. A refracting telescope is easier to use, but a reflector will generally give brighter images and a wider field of view In this case, we're referring to telescopes in the $250 - $300 range. Reflectors cost less per inch of aperture - the diameter of the primary mirror or lens. The greater the aperture, the more light the telescope will gather and the more you'll be able to see in the sky.