Astrolabe

Astrolabe (from two Greek words signifying 'to take the stars'), the name given by the Greeks to any circular instrument for observing the stars. Circular rings, arranged as in the Armillary Sphere (q.v.), were used for this purpose. A projection of the sphere upon a plane, with a graduated rim and sights for taking altitudes, was known as an astrolabe in the palmy days of astrology. It has been superseded by the more perfect instruments of modern astronomy. Chaucer published a learned Treatise on the Astrolabe in 1391, edited by Professor Skeat in 1872 for the 'Early English Text Society.'