The '''astrolabe''' was a compact round disc used to observe and calculate the position of [[celestial bodies]] before the invention of the [[sextant]]. It was the most widely used astronomical instrument of the Islamic and [[Medieval]] periods.
Astrolabes usually consisted of a flat disc with a sighting rod that could be pivoted to point at the [[Sun]] or bright stars. From the altitude of the Sun or star above the horizon, the local time could be estimated. <ref>A presentation for the Man & Technology Course (ES103) @ SUNY Farmingdale,by Gary Agranat & Dave Delligati, Fall 1980. [http://members.aol.com/chopstcks/gca7sky/astrolabe.htm]</ref> Astrolabes were usually constructed of light metals, such as [[copper]] or [[zinc]], however elaborate ornamental gold and silver astrolabes were created for wealthy rulers such as [[Pope Alexander VI]] and [[Suleiman the Magnificent]].
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