A telescope mount with one axis parallel to the Earth's rotation axis, and the other at right-angles to it.

This equatorial mount enables the telescope, once locked onto a star's position, to track or to follow the star using a motor drive to compensate for the earth's rotation.

Most large telescopes are mounted in this way, but the altazimuth mount, with its simpler construction, is becoming more popular.

An "altizimuth mount" is a mounting for astronomical telescopes that has separate axes for horizontal and vertical rotation.

Because celestial objects move in arcs across the sky, tracking their motions with an altazimuth mount requires adjustments of both axes.