BD479 Astrolabe by listentoreason on Flickr.

Via Flickr:
New York Metropolitan Museum of Art, April 2003.
Artifact information at The Met - Yemen, 1291AD

Wikipedia: Astrolabe:
“The astrolabe is a historical astronomical instrument used by classical astronomers, navigators, and astrologers. Its many uses included locating and predicting the positions of the Sun, Moon, planets and stars; determining local time given local latitude and vice-versa; surveying; and triangulation.

In the medieval Islamic world, they were used primarily for astronomical studies, as well as in other areas as diverse as astrology, navigation, surveying, timekeeping, Salah prayers, and Qibla. Astrologers of the European nations used astrolabes to construct horoscopes.”