1. (Science: astronomy) An instrument for observing or showing the positions of the stars. It is now disused.
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 It is now superseded by the quadrant and sextant.
2. A stereographic projection of the sphere on the plane of a great circle, as the equator, or a meridian; a planisphere.
Origin: oe. Astrolabie, astrilabe, OF. Astrelabe, f. Astrolabe, LL. Astrolabium, fr. Gr.; star _, to take.