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submitted: 2008-04-05 05:30:03 | by: DavidWildash
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Binoculars with a strength of 7 X 35 can actually be a better choice than a telescope. Binoculars are more portable and convenient, relatively inexpensive, and it's wiser to get cheap binoculars over a cheap telescope. With the 7 X 35 binoculars, the first number stands for the eyepiece magnification and the second number is the aperture in millimeters. Binoculars of this caliber are lighter and easy to hold.

If you are considering a telescope there are essentially three types available to the amateur astronomer.

Refractors are the most readily recognized type and consist of lenses at both ends of a tube. Whatever you do avoid the cheap models sold by department, nature/science and toy stores. They quote large magnifications, but their small apertures make them useless for astronomy. Remember a telescope's most important job is to collect light, not magnify a image. A normal terrestrial telescope has an extra lens to ensure the image is the right way up. However extra lenses cut down the amount of light reaching the eye. The one thing an astronomer wants to avoid is reducing light and therefore information. So the correcting lens is omitted and a true astronomical telescope gives an upside down (inverted) image. Lenses can create false rainbow tints around very bright objects like planets. This is called chromatic aberration and can be ignored or corrected by a filter. Refractors generally cost more per inch of aperture than other types of telescope, and those of more than 4-inch (100mm) aperture are rather long and cumbersome. However smaller good quality ones can make excellent beginner instruments.

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.

The third type of telescope is the Schmidt-Cassegrain. This uses lenses and mirrors to fold the light path back on itself within a compact tube. They are generally cheaper than refractors, but dearer than reflectors. They are more portable and easier to handle than the other two.

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.

By joining a local astonomy club or checking a library, you can evaluate different types of instruments. Also, astronomy magazines have reviews as well as advertising for good telescopes.

Purchasing the largest aperture you can find is the best idea, but don't buy a telescope larger than you can lug around. Smaller telescopes are easier to set up and more convenient to use. You also don't want to waste your money on a large telescope if atmospheric pollution is high in your area, as this will prevent the telescope from giving you its best results.

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.

Along with finding celestial objects, telescopes also follow the movement of those objects. The instrument must be moved repeatedly to keep the object in focus, and different mounts and drives make this possible. Electronic drives will point a telescope in the right direction, but the sturdiness of the mount is the most important thing.

It is important to realize that many textbook and telescope advertisement photos are long exposures with false colors added. Stars seen through a telescope will always look like points of light, and you will not see color in dim objects. The eye is not sensitive enough.

So, let's talk about what you will see with a beginner telescope. With just a 75mm refractor or 150mm reflector, you can see nebulae, galaxies, moon craters, Saturn's rings, and even some of Jupiter's moons. All of these are amazing objects to view as you learn about the night sky.

About the Author

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

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