Astrolabe, 14th century

A flat spherical astrolabe, known as the astrolabe (from Ancient Greek ἀστρολάβος, astrolabe, via medieval Latin astrolabe, "taking the stars"), is a copper astronomical instrument for analog observation and computation. A tool with multiple functions, which makes it possible, in particular, to measure the height of stars, including the Sun, and, accordingly, to determine the time of observation and the direction of the star. Its design, which has Greek origins in antiquity and was later perfected by the Arabs, is based on a planar projection of the celestial vault and the local sphere, known as the stereographic projection.
Astrolabe, 14th century