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.



For those amateur astronomers, there are three types of telescopes available.

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 next type of telescope is called the reflector, and these are usually comfortable because of the eyepiece position. In this telescope, light reflects off mirrors as is travels down the telescope tube and through the eyepiece on the side. In order to be as useful as a refractor, the reflector must be larger in size. Although they don't create false rainbow images, the main mirror on a reflector often needs to be readjusted, and there are kits for this. A popular type of reflector is called a Dobsonian, and this is convenient because it has a mount instead of 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.

You may be able to evaluate the different instruments by joining a local astronomy club or attending one of their star parties. Check at your local library. You can also look in a reputable astronomy magazine for reviews and manufacturers advertising good quality 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.

It's best to spend most of your money on a buying a large aperture instead of telescope accessories. Doubling the aperture number will calculate the maximal practical magnification: i.e., a 70mm aperture will have a maximum magnification of 140x. Do not buy an eyepiece that is stated to stretch magnification past maximum aperture value. Start simple with eyepiece choices, such as a Kellner, which is a good all around eyepiece. If you place a Barlow lens between an eyepiece and focuser, magnification can be tripled.

A telescope also magnifies the movement of objects across the sky and the instrument will have to be moved repeatedly to keep the object in the field of view. To cope with this different mounts and drives have been devised that enable the telescope to follow the moving object. You can get electronic drives to point the telescope, but the most important thing is that the mount is sturdy.

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.