tags: astronomy hipparchus

The astrolabe is a historical astronomical instrument used by classical
astronomers, navigators, and astrologers. Its many uses included
locating and predicting the positions of the Sun, Moon, planets and
stars; determining local time given local longitude and vice-versa;
surveying; and triangulation.

In the medieval Islamic world, they were used primarily for
astronomical studies, as well as in other areas as diverse as
astrology, navigation, surveying, timekeeping, Salah prayers, and
Qibla. Astrologers of the European nations used astrolabes to
construct horoscopes.

There is often confusion between the astrolabe and the mariner's astrolabe.
While the astrolabe could be useful for determining latitude on land, it was
an awkward instrument for use on the heaving deck of a ship or in wind. The
mariner's astrolabe was developed to address these issues.

An early rudimentary astrolabe was invented in the Hellenistic world
in either the first or second centuries BCE and is often attributed to
Hipparchus.