Buying a Telescope
First a couple of general remarks. The main light gathering element of a telescope is called the objective. If the objective is a lens, the telescope is refracting; it the objective is a mirror, the telescope is reflecting. The diameter of the objective controls how much you can see, both in detail and in dimness of objects. The bigger the objective, the better -- always assuming that the optical quality is high. Refracting telescopes may give slightly sharper images, but they are much more expensive for the same size, and esentially all larger telescopes are reflecting. Do not be overly concerned with the magnifying power of the telescope. By changing eyepieces, any telescope can be operated at a wide range of powers, and high powers are not necessarily the best for many purposes.
An important consideration for anyone living in a metropolitan area who is thinking of buying a telescope is: Are you going to spend the time driving away from the city to reach a dark sky site, or do you primarily plan to observe from the city? From the city you are limited to the following objects:
Of course, these are some of the prettiest objects, and many people are satisfied to show their neighbors the rings of Saturn and the craters of the moon from their back yards in the city. To see these objects your cheapest option is to get a small refractor with a 60- 100 mm primary lens from Meade, Celestron, Fedco, Tasco, etc. They cost $300 - 500, produce sharp images, are easy to setup, and require no optical alignment. Look carefully at the mount when you are buying, the mountings are sometimes flimsy and difficult to operate. An even cheaper option is to get an 20 - 40 power nature viewing scope for about $100. If you have more money to spend, on the order of a thousand or two, get an 8" Celestron or Meade mentioned below.
If you live in a dark sky area, or are planning to visit such places regularly, you have another decision to make: Do you want to just look at interesting objects, or do eventually plan to photograph them? To photograph the mounting must be equitorial with a clock drive so the telescope can follow the motion of the stars. An excellent choice that covers all bets is an 8" Meade or Celestron. They cost from $1000 - 2500, depending on accessories, have an equitorial mount, work well inside or outside the city, and have good resale value. Be aware that if you go into astrophotography, you can easily spend another thousand dollars getting the necessary accessories, not even counting the camera.
In the 70's John Dobson of the San Francisco Sidewalk Astronomers pioneered a new type of mount, very simple and cheap to build, and very stable and easy to use. These "Dobson" mounts are not equitorial and cannot be used for photography without expensive additional parts, which possibly have not been perfected. But you cannot beat this type of telescope in viewing per unit dollar. Orion has a 12.5" for about $900, and Coulter has a 13" for $800. These 12 and 13" telescopes will give you much better views of the deep sky objects, the nebulae, galaxies, and star clusters, at a dark sky site than the 8 inchers.
Some final comments: You need a good finder to locate the interesting objects with your telescope. Most telescopes are supplied with inadequate finders. Get a 50 -60 mm accessory finder plus an accessory reflex finder (which shows you where the telescope is pointed in the sky). Good eyepieces greatly enhance viewing pleasure. The wide angle Naglers, though expensive ($200 - 400 @), are well worth the cost. Orion (800)-447-1001 and other companies sell these accessories.
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