Ottoman Turkish instrument made in 1671 by Alî al-Za’tarî. Astrolabes are intended for locating and identifying celestial objects. They are also used for timekeeping using pre-defined position tables of the sun and other stars. During the Middle Ages in the Islamic world, astrolabes were used daily for the regulation of Muslim prayer times. On loan from the Bosphorus University Kandilli Observatory. H: 12.5 cm Ø: 11 cm