This rare 11th century Islamic astrolabe is one of the oldest yet discovered

This isn't just an incredibly rare object. It's a powerful record of scientific exchange between Arabs, Jews, and Christians over hundreds of years.

Before the emergence of the sextant, astrolabes were mostly used for astronomical and astrological studies, although they also proved useful for navigation on land, as well as for tracking the seasons, tide tables, and time of day.

Read at Ars Technica