Telescopes for the Amateur Astronomer | Astronomy

By DavidWildash
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Although most people think of telescopes it may be best to consider binoculars first. They are portable, convenient and relatively inexpensive. Cheap binoculars are better than a cheap telescope. Consider something like 7 x 35 binoculars. The 7 is the magnification produced by the eyepiece, the other number is the aperture in millimeters. This size is light and easy to hold.

There are three types of telescopes available for beginning astronomers.

Refractors consist of lenses at both ends, and the most recognized type of telescope. They generally cost more per aperture inch than other telescopes, but their size makes them ideal beginner telescopes. It's best to avoid cheap department store models, as these quote large magnifications but have small, useless apertures. The job of a telescope is to collect an images light, not magnify it, so large magnifications actually make things worse and can alter data. Earthly telescopes usually have extra lenses to make an image appear right side up, but this extra lense can cut down the amount of light that reaches the eye. Therefore, the extra lense is left out of astronomical telescopes, which leaves images upside down. Since lenses can create false rainbow images around really bright objects, it's best to buy a filter to help correct the problem.

The second type of telescope is the reflector. Light travels down a tube before reflecting off a couple of mirrors and through an eyepiece on the side of the tube. Reflectors need to be larger than a refractor to be equally useful. They do not suffer chromatic aberration, but the main mirror may occasionally need repolishing or realigning (collimating). There are kits available for this. Reflectors are often the most comfortable telescopes to use because of the eyepiece position. You don't have to kneel and possess an elastic neck to look straight upwards as you would with a reflector. A popular type of reflector is the Dobsonian, which has a mount near the ground rather than a tripod.

Finally, there is the Schmidt-Cassegrain telescope. This telescope uses both lenses and mirrors to fold light back onto itself inside a compact tube. These cost less than refractors and are dearer than reflectors, and are overall more portable and easier to handle.

The specifications of a telescope may quote numbers which can affect the exposure needed if you pursue astrophotography. They will not affect the image you see; however, it's best to become familiar with the sky before you start with astrophotography.

If you join a local astronomy club, you may be able to look into the different types of instruments, or you can just check your local library. Also, reputable astronomy magazines are available for reading reviews on quality telescopes, as well as manufacturers advertising.

Even though you should purchase the largest aperture you find, keep in mind you may not want a large telescope as you may have to carry it around. Smaller telescopes are easier to set up and use, and high pollution in your area can keep a large telescope from producing results to its full potential.

The best way to calculate the maximum practical magnification is to double the aperture number: i.e. a 60mm aperture shoudl yield a 120x magnification. You shouldn't waste time on buying telescope accessories, but should instead invest in the largest aperture you can find. However, don't be tempted to purchase an eyepiece that claims to stretch magnification beyond the calculated aperture value. Start off simple in terms of eyepieces. A Kellner eyepiece is a great general purpose piece, and if you place a Barlow lens between it and a focuser, magnification may be tripled.

In order to keep a moving object in view, a telescope may have to be moved repeatedly. To help with this, mounts and drives have been created. Electronic drives will help point the telescope, and it's important to have a sturdy mount.

It's important to know that many textbook and telescope advertisement photos are long exposures and have been given false colors. Since the eye isn't sensitive enough, stars will always look like small points of light and color will not be seen in dim objects.

Now, what will you be able to see with a novice telescope? With a 75mm refractor or 150mm reflector, you may see galaxies, nebulae, Saturn's rings, the large Jupiter moons, and countless craters on the moon. There are plenty celestial objects to help introduce you to the night sky.

About the Author

David Wildash shares information and resources on his website about Telescopes , and you can read more about buying a telescope

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