Telescope Mounts
Telescopes are offered on either altitude-azimuth (or altaz) mounts, which move up-down (altitude), left-right (azimuth), or equatorial mounts, which are tilted to align with the rotational (polar) axis of the Earth.
Altaz mounts are generally lighter and simpler to use, and are preferred if the telescope is to be used both for both astronomy and daytime observing (or for daytime observing only). The better ones offer slow-motion controls to aid in moving the scope by small increments, and are useful for powers up to about 150x. The Dobsonian mount is a variation on the altaz mount. It employs unconventional (for telescopes) materials like plywood and Teflon in a compact mounting that moves easily, is extremely stable, and can adequately support large telescopes at a very low cost. Though there are no mechanical slow-motions or electric drives on a Dobsonian, a well-made example glides so smoothly on the Teflon bearings that with a little practice it is quite easy to track objects manually at 200x or more!
Equatorial mounts are designed specially for astronomy, and are not recommended for terrestrial viewing. Their advantage is that they allow easier tracking of the stars across the sky. This motion can be achieved with either a single manual slow-motion control or an electric motor drive (or clock drive). The easier viewing they provide at high power makes equatorials preferred by observers who are most interested in the Moon and planets. Also, you’ll need an equatorial mount if you want to do astrophotography.
Reprinted with permission from Galileo Telescopes