Sloane Astrolabe, c.1300 AD
462 (diameter) x 12 (thickness) mm

Astrolabes (Greek for “star-finders”) were technological marvels of the Middle Ages. They used the position of the sun and stars for finding the time, surveying, navigation and astrology. With origins in ancient Greece, astrolabes were fully developed in the Islamic world around the end of the 1st millennia. This mathematical and astronomical knowledge then moved into Europe. This unusually large and elegant brass example is the earliest surviving English astrolabe, made around 1300 AD. These early European instruments often celebrate their Islamic roots in their decoration, such as the foliate scrolls seen on this instrument.
Astrolabes have a distinctive “rete” or “net”, with each point representing a star – here each point is in the form of a mythical creature. The rete is rotated over a background of the celestial sphere, accurately representing the positions of the stars in the heavens for a given time. This background is formed of interchangeable plates, here engraved for seven latitudes from 42° to 55°, allowing the instrument to be used across most of Europe.
This astrolabe was owned by Sir Hans Sloane, whose extensive collection formed the foundation of the British Museum.

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