The structure that supports a telescope and allows it to be pointed at a chosen part of the sky. A mounting should hold the telescope firmly and allow it to be moved so that it can follow objects across the sky as the Earth rotates. This can be done either with a motor drive or with controls known as slow motions. Telescope mountings fall into two main categories: altazimuth and equatorial. The part that allows the telescope to move is often referred to as the head, which may be mounted on either a pillar or a tripod.