Telescopes Buying Guide
by Staff Writer
Invented by accident in 1608 by an eyeglass maker in Holland, telescopes have allowed astronomers to explore the far reaches of the universe. While professional astronomers use massive optics housed in special observatories to conduct their research, amateur astronomers can have great fun and enjoy the beauty of outer space and the Earth using much smaller and far less expensive equipment. Here is some information to help you understand the basic technologies so you can choose the telescope that will work best for you.
Buying a Telescope:
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- Telescope magnification:
Magnification is important; after all, the whole idea behind a telescope, or optics and binoculars in general, is that it magnifies distant objects so you can see them more clearly. However, any seasoned astronomy enthusiast will tell you that telescope magnification is just one of several factors that go into making a good telescope, and probably not even the most important one. In fact, as you browse through telescopes, you may notice that most of them don't list their magnification power prominently. A telescope with magnification between 100x and 200x is ideal for most home astronomy because as magnification goes up, image quality goes down, and even telescopes with price tags in the thousands have trouble producing clear images at 400x magnification.
- Telescope aperture:
On the other hand, telescope aperture is more important than you may think, possibly the most important factor you should consider when shopping for a telescope. Telescope aperture refers to the diameter of the lens of mirror used in a telescope. It affects the magnification of a telescope, but more important, it affects the amount of light that enters a telescope, which makes a huge difference in the quality of the images you can see through a telescope. Basically, the larger the aperture, the more clear and bright the image you can see. A telescope with a narrow aperture, say 50 mm, may be able to magnify a comet 200 times, but the resulting image will be so dim as to be useless. A telescope with a 250-mm aperture that magnifies a comet 200 times will produce an image that is bright and clear.
- Telescope quality:
Aperture is almost everything in the world of telescopes, but not quite. When you're shopping for a telescope, you should also pay attention to the quality of the instrument. Telescopes are precision instruments, and as quality goes up, the clarity of the images that you see will go up as well. If you're deciding between a high-powered instrument of questionable quality and a lower powered instrument of good quality, choose the quality instrument.
- Refractor telescopes:
There are two main types of telescopes: refractor telescopes and reflector telescopes. Refractor telescopes use a lens to gather and focus light (when light bends as it moves through the lens, it's called "refraction"). Refracting telescopes have a number of advantages that make them ideal for home astronomers. The tubes of refracting telescopes are sealed, which makes them both durable and low-maintenance; you will only need to clean off the lens of a refracting telescope occasionally. Also, at low and average powers, refractor telescopes can produce excellent images. However, large glass lenses are difficult and expensive to produce in large sizes, and glass lenses create something called "chromatic aberration," which produces halos of color around objects.
- Reflector telescopes:
Reflector telescopes use a curved mirror to reflect and focus images and have become one of the most popular kinds of telescopes available. The main advantage that mirrors have over lenses is that large mirrors, 10 inches and more, can be made far more easily and for less cost than large lenses. Also, reflector telescopes produce less distortion than refractor telescopes when they're used at high powers. If you want a telescope with an exceptionally large aperture, then you probably want a reflecting telescope. Some of the disadvantages of reflecting telescopes are that they're more fragile than refracting telescopes and the mirrors require periodic cleaning and adjusting.
Eyepieces: Telescopes usually have removable eyepieces. You can enhance your viewing experience by buying telescope eyepieces with high-quality lenses and filters that can sharpen the deep-space objects you're viewing.
Binoculars: Binoculars can make an excellent companion to a telescope. Since binoculars have a wide field of view, they're perfect for locating objects that you want to point your telescope at. If you aren't sure if you want to buy a telescope or if you're star-gazing on a budget, you'd be amazed at how much you can see with just a decent, inexpensive set of binoculars.