What are Go-to Drives?
Go-to drives are a certain type of motorized telescope mount. Both axes of a Go-to mount are powered by a motor and connected to a microprocessor or computer-based control system. The function of a Go-to is to allow a user to find any star in the night sky. To do this, they are supplied with a database of known stars and their relative location in the skies, and once they are given the location of a reference star, a Go-to mount can automatically turn the telescope it supports to point to the location of any other star whose location is stored in its database, which is usually derived from the Messier or New General Catalogue of stars. Some Go-to mounts can even find the locations of major bodies in the solar system, such as the Sun, Moon and other planets.
Go-to drives will ask for the location (latitude and longitude) as well as the time and date of the telescope when they are powered up for use. This can be done manually or it can be supplied through a GPS. Additionally, for altazimuth microscopes, the Go-to drive will ask for the location of a known star for use as a reference point. This is called pre-alignment and has been mentioned above. Once the location of the star is entered, the Go-to drive can then turn the telescope it mounts to face the location of any other star whose location it knows, as mentioned above. However, it is generally recommended to use another reference star to improve accuracy. This is because the mount might not be level with the ground, and so while the drive will point accurately to objects near the reference star, it may lose accuracy when acquiring other stars further away from the reference star. In addition, if the user does not enter the correct location / time, the Go-to drive’s accuracy will be reduced. For instance, one-degree inaccuracies in the latitude or a 4-minute inaccuracy in the time may result in the telescope pointing a degree away from the desired target.
Equatorial mounts are calibrated in a somewhat different way. The telescope must be sighted on either the north or south celestial pole. The Go-to drive will then point the telescope toward a bright star and request that it be centered in the eyepiece. After this is done, the Go-to drive will know its orientation with respect to the night sky, and can orient itself to any star that it knows. Giving it a second star to reference, like altazimuth telescopes, can increase its accuracy.
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