Astrolabes: How do they work?

Astrolabes: How do they work?
Accession number: 
Museum of the History of Science, Oxford

Astrolabes are multifunctional astronomical instruments and can be used to tell the time, to determine the length of day and night, to simulate the movement of the heavenly bodies, for surveying and for astrological purposes. By observing the positions of the stars or sun, measuring their inclination and aligning the movable parts of the astrolabe accordingly, one can create a flat model of universe for that moment in time. The annotations above guide one through its different parts and how they relate. 

To find out more about astrolabes, how they work and their history, see the description of 'Western Astrolabes' on the Starry Messenger website.