Equatorial mounting

An equatorial mount is a mount used for moving a telescope or camera along two perpendicular axes of motion known as right ascension and declination. Equatorial mounts are often equipped with a motor drive for automatic tracking of objects across the night sky. They may also be equipped with setting circles to allow for the location of objects by their celestial coordinates.
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A mounting for a telescope, designed so that the two axes, which support it, are aligned, one to the polar axis and one to the equator of the Earth. This allows use of the right ascension and declination coordinate system. There are many variations on the designs of equatorial mounting but all rely on the principle that to counteract the rotation of the Earth, the telescope need only be driven around the polar axis.