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Polar alignment is the act of aligning the rotational axis of a telescope's equatorial mount or a sundial's gnomon with a celestial pole to parallel Earth's axis. Alignment methods [ edit ]
A large German equatorial mount on the Forststernwarte Jena 50cm Cassegrain reflector telescope. An equatorial mount is a mount for instruments that compensates for Earth's rotation by having one rotational axis, called polar axis, parallel to the Earth's axis of rotation. [1] [2] This type of mount is used for astronomical telescopes and cameras.
A polar mount is a movable mount for satellite dishes that allows the dish to be pointed at many geostationary satellites by slewing around one axis. [1] It works by having its slewing axis parallel, or almost parallel, to the Earth's polar axis so that the attached dish can follow, approximately, the geostationary orbit, which lies in the plane of the Earth's equator.
A key modification of the original design is the hinged suspension of the drive rod, which avoids binding, as well as a central tripod mount that can be moved along the supporting truss tubes to better balance for lighter or heavier loads according to their orientation. For proper polar alignment, a 3-way tripod or azimuth wedge is required ...
Slewing or mechanically driving the mount's polar axis in a counter direction to the Earth's rotation allows the telescope to accurately follow the motion of the night sky. Equatorial mounts come in different shapes, include German equatorial mounts (GEM in short), equatorial fork mounts , mixed variations on yoke or cross-axis mounts, and ...
The equatorial describes the sky as seen from the Solar System, and modern star maps almost exclusively use equatorial coordinates. The equatorial system is the normal coordinate system for most professional and many amateur astronomers having an equatorial mount that follows the movement of the sky during the night. Celestial objects are found ...
Even with some inaccuracies in polar alignment or the perpendicularity of the mount, setting circles can be used to roughly get to a desired object's coordinates, where a star chart can be used to apply the necessary correction.
Clock drive mechanism in the pier of the German equatorial mount for the 8-inch refracting telescope at Aldershot Observatory.. In astronomy, a clock drive (also known as a sidereal drive or field rotator) is a motor-controlled mechanism used to move an equatorial mounted telescope along one axis to keep the aim in exact sync with the apparent motion of the fixed stars on the celestial sphere.