Equatorial mounts must have one axis- the Right Ascension, or polar, axis aligned with the Earth's axis of rotation in order to be able to track the rotation of the earth. This is called Polar Alignment.
Method of aligning a mount to enable proper tracking. Required for equatorial mounts.
a small finderscope, often mounted in the polar axis of a German equatorial
In order for a telescope on an equatorial mount to properly track the sky to compensate for Earth's rotation, the mount must be correctly polar aligned.
This is a procedure by which the central axis of the telescope is aligned with the North Celestial Pole. This allows a telescope to use equatorial coordinate system, which is the universal astronomical coordinate system.
The alignment of an equatorial mounting's polar axis parallel with the axis of rotation of the Earth.