Reflectors - Refractors - Binoculars - Schmidt Cas- Mountings - Eyepieces - Filters - Goto Telescopes

The importance of mountings for your telescope cannot be over stated. The mounting is as important to your telescope as tires are to a car. If the mounting is unsteady, your telescope will be useless. Unfortunately, many mounts and tripods supplied with department store instruments are inadequate at keeping the telescope steady. The best way to judge a mount is to actually look through a telescope before you buy. Or you can ask actual astronomers with experience. Attend a star party, such as the ones held frequently by local astronomy clubs. With this said, lets take a look at the different types of mounts so one can be chosen that meets your needs and wallet.

There are two basic types: Alt-azimuth and equatorial. An alt-azimuth mounting swivels left to right parallel to the horizon, and up and down perpendicular to the horizon. These are the least expensive, and are easy to set up and use. However, they do not track the stars. Because of the earth's tilt, celestial objects appear to rise in the east and make an arc across the sky, reaching a high point directly south, and then arcing down to the west. Stars in the north circle around the pole star, Polaris. See the diagram below.

An equatorial mount has one axis fixed, pointing to Polaris. The other axis follows the movement of the stars with one motion. A clock drive attached to that axis will automatically move the telescope to compensate for the earth's rotation. An alt-azimuth mount will track the stars as well, using a computer to move the telescope the appropriate amount in each direction.

However, if you wish to do long exposure astrophotography, an equatorial mount is required to eliminate field rotation. Field rotation occurs because the orientation of the image rotates as it travels in an arc across the sky.

Of the types of equatorial mounts used, the fork and German Equatorial are the most common. The fork works well with short tubes, such as Schmidt-Cassegrains, but can be awkward to use in certain viewing positions. The German Equatorial is popular for astrophotography but is inherently unsteady and needs to be as large and beefy as possible to eliminate vibrations.

The least expensive, easiest to use, and simplest to construct, is the Dobsonian style, named for its inventor John Dobson. Although built of almost any material, wood is the most common. The very large bearing surfaces ensure a steady image. Teflon bearings floating on Formica surfaces make hand tracking an easy process. The Dobsonian box can be built large for Newtonian reflectors of very large size. Observers who want a lot of light gathering, are not interested in astrophotography, and are on a budget, the Dobsonian design makes the most sense.