Description and use of an Astrolabe.
An astrolabe is a very ancient astronomical computer for solving problems relating to time (what time is it ?) and the position of the Sun and stars in the sky.
The history of the astrolabe begins more than two thousand years ago.
The principles of the astrolabe projection (stereographic projection) were known before 150 B.C., and true astrolabes were made before A.D. 400.
