GoTo (telescopes)

In amateur astronomy, "GoTo" refers to a type of telescope mount and related software which can automatically point a telescope to astronomical objects that the user selects. Both axes of a GoTo mount are motor driven and are controlled by a computer. It may be either a microprocessor-based integrated controller or an external personal computer. This is contrasted to the single axis semi-automated tracking of a traditional clock drive mount. The user can command the mount to point the telescope to a right ascension and declination that the user inputs or to objects in a pre-programmed data base including ones from the Messier catalogue, the New General Catalogue, and even major solar system bodies (the Sun, Moon, and planets).

Like a standard equatorial mount, equatorial GoTo mounts can track the night sky by driving the right-ascension axis. Since both axes are computer controlled GoTo technology also allows telescope manufacturers to add equatorial tracking to mechanically simpler alt-azimuth telescope mounts.

GoTo mounts are pre-aligned before use. When they are powered on, they may ask for the user's latitude, longitude, time, and date (they can get this data from a GPS receiver connected to the telescope, or even built into the telescope mount itself and the telescope mount controller can have a real time clock).

Alt-azimuth GoTo mounts need to be aligned on a known "alignment star", which the user will centre in the eyepiece. From the inputted time and location and the star's altitude and azimuth the telescope mount will know its orientation to the entire sky and can then find any object.

For accuracy purposes, a second alignment star, as far away as possible from the first and if possible close to the object to be observed, may be used. This is because the mount might not be level with the ground; this will cause the telescope to accurately point to objects close to the initial alignment star, but less accurately for an object on the other side of the sky.

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