An Astrolabe a sort of computer of the ancients. Some of these tools were created over two thousand years ago when people thought the earth was the center of the universe. Movable components on the astrolabe are then set to a specific time and date and then the sky is represented on the face of the instrument. This instrument was mainly used to make astronomical measurements, typically of the altitudes of celestial bodies, and in navigation for calculating latitude, before the development of the sextant.