the various parts of a 18th century astrolabe made in North Africa.

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.

The first astrolabes were made in the 3rd century but advanced brass astrolabes did not appear till the middle ages (8th and 9th century).

The plates of this instrument are made of brass but are unusual in that they have been electroplated in gold. The thin layer of gold has been worn off over the years.

This instrument is a copy of a much older instrument used in the 17th century. Astrolabes were often copied and given as gifts. This one is a medium quality copy found in a souk in Marrakech.

Think of it as 18th century "bling": In the 16th and 17th centuries, the possession of an astrolabe lent an element of prestige and intelligence to the owner.

Now it's just a hunk of brass that no one knows how to use. The mathematical principles behind its use are fairly complex. Basically it's a mechanical device for predicting the movement of celestial bodies (usually the moon, sun, planets, and principal stars). It was used in the Arab world in may ways. For one, to determine the times of sunset and sunrise as well as lunar cycles. It could also be used for navigation to determine ones approxiamate longitude and latitude. The North African Moors brought the astrolabe to Europe and it was quickly made popular for navigation and celestial mechanics.

As an instrument of astrology it was used extensively by Sufis (Islamic mystics; especially in the Persian world) to create astrological maps based on events. This small one is not as astrological astrolabe but rather an astronomical one. Astrological astrolabes have detailed astrological charts and maps on the inside and back of the mater. This one has mathematical tables instead.