Planispheric Astrolabe from Muslim Spain

The astrolabe is an astronomical calculating device used from ancient times into the nineteenth century. Measuring the height of a star using the alidade on 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. Engraved plates that fit below the rete have scales of altitude and azimuth (arc of the horizon) for specific latitudes. This brass metal astrolabe has backplate with throne, handle, ring, the end of a cord, an alidade with pin, a rete, five plates, a ringlet, and a wedge at the front that holds the instrument together. The instrument is signed: [. . .]ana ‘ahu al-[. . .]asan ben A[. . .]mad al-Ba[. . .] [. . .]u[. . .]i.

Reference:

For a detailed description of this object, see Sharon Gibbs with George Saliba, Planispheric Astrolabes from the National Museum of American History , Washington, D.C.: Smithsonian Institution Press, 1984, pp. 17, 160, 163-165. The object is referred to in the catalog as CCA No. 2568.

Where this page came from

This page was imported from Smithsonian National Museum of American History. Released by the Smithsonian Institution under CC0 through Smithsonian Open Access.

Nobody has written it yet — it is the source material at a new address, which is why search engines are asked to skip it and why no one earns from it. It is up for grabs: take it on, and it is yours to rewrite and to earn from.