In general a typical telescope consists of a body, where a primary mirror collecting light is set, and a mount, which supports the body. A telescope is classified into two major types, refractor and reflector, whether it uses a lens or a reflecting mirror as a primary mirror. Furthermore, there are several types of the focus. A mount is also classified into two major types, an equatorial type and an alto-azimuth type.

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An astronomical telescope is classified into a refractor, where light is collected by a convex lens, and a reflector, where light is collected by a concave mirror. Since it is difficult to make and hold a large lens, the aperture limit of the refractor is about 1 meter. Hence, all of the big telescope are the reflector.

Due to the spin of the Earth, celestial objects revolve every day in 15 degree per hour (diurnal motion). In order to observe a celestial body from the ground, a telescope must track and guide the body.
The mount supporting a telescope body is classified into an equatorial type and an alto-azimuth type. The former has a polar axis and a declination axis, while the latter has a horizontal axis and a vertical axis.
The equatorial type is easy to track celestial objects, while the alto-azimuth type is mechanically stable. For the recent modern big telescope, often adopted is an alto-azimuth type under a computer control.