An equatorial mount is primarily built the same as an altazimuth mount with one axis aligned parallel to the axis of rotation of Earth by pointing it at the North or South celestial pole.
This type of mount moves the telescope in two axes:
Refractor on Equtorial GoTo mount
With an equatorial mount, polar axis must be parallel with the rotational axis of the Earth. For movement in the polar axis, the motor turns the mount at the same rate as the Earth's rotation. The declination axis is perpendicular to the polar axis. It is used to make adjustments in declination – allows the telescope to be pointed at celestial objects of different declinations. To keep the celestial object centred in the eyepiece, the user needs to turn only the polar axis to track the object.
An equatorial mount allows the telescope to move in an arc that is perfect for tracking stars as they move across the sky.
Compared to an alt-az mount, the movement of an equatorial mount is continuous, which is perfect for: