French Planispheric Astrolabe

The astrolabe is an astronomical calculating device used from ancient times into the eighteenth century. Measuring the height of a star using the back of the instrument, and knowing the latitude, one could find the time of night and the position of other stars. The openwork piece on the front, called the rete, is a star map of the northern sky. Pointers on the rete correspond to stars; the outermost circle is the Tropic of Capricorn, and the circle that is off-center represents the zodiac, the apparent annual motion of the sun. This brass astrolabe has a body and throne plate, a handle, ring, rete, alidade, pin, wedge, and index arm. It is signed I. Galois. Other inscriptions are in ...