%astrolabe%

n. [ OE. astrolabie, astrilabe, OF. astrelabe, F. astrolabe, LL. astrolabium, fr. Gr. 'astrola`bon; 'a`stron star + &unr_;, &unr_;, to take. ] 1. (Astron.) An instrument for observing or showing the positions of the stars. It is now disused. [ 1913 Webster ]

☞ Among the ancients, it was essentially the armillary sphere. A graduated circle with sights, for taking altitudes at sea, was called an astrolabe in the 18th century. It is now superseded by the quadrant and sextant. [ 1913 Webster ]

2. A stereographic projection of the sphere on the plane of a great circle, as the equator, or a meridian; a planisphere. Whewell. [ 1913 Webster ]