What is an astrolabe used for?

The astrolabe was used to measure one's geographical position by measuring the altitude of heavenly bodies.

Who invented the astrolabe?

It is not known by whom or when the astrolabe was invented, but one figure frequently credited by some historians as being the inventor of some form of the astrolabe is the Greek Hipparchus of Nicea in the 2nd century BCE.

What was the astrolabe used by explorers?

The astrolabe was a device used by explorers like Christopher Columbus to help them navigate since with it they could measure the altitude of certain stars and so calculate their latitude.

Astrolabe Timeline

Definition

The astrolabe is an astronomical instrument used from around the 6th century to measure time and position by determining the altitude of heavenly bodies like the Sun and certain stars. Measurements were taken in reference to the viewer's horizon and the meridian and using a representation or map of the sky with a measuring scale engraved on the instrument itself.

More about: Astrolabe

Timeline

100 CE - 170 CE
Ptolemy describes the principle of the astrolabe - sterographic projection.
c. 1000 CE
Knoweldge of the astrolabe filters through Muslim Spain to the rest of Europe.
1391 CE
Geoffrey Chaucer wrties an explanation of how to use an astrolabe in his Tractatus de Conclusionibus Astrolabii.
1510 CE
Johannes Stoeffler explains the astrolabe in Elucidatio fabricae ususque astrolabii.