Astrolabes are amongst the most sophisticated scientific instruments ever made. “The word astrolabe is a Greek-Arabic hybrid that literally means “star-holder,” an apt description for a device that indicates the positions of the stars, sun, moon and planets. Essentially, it is a map of the heavens, depicting the apparent movements of celestial bodies in terms of celestial latitudes and longitudes, combined with slide rule-like features that allow calculation.”*
Invented by the Greeks in about the second or third century BC, the astrolabe was further advanced by the Arabs in the eighth to eleventh centuries CE. The Arab treatises on the astrolabe published in the ninth century indicate their familiarity with the instrument, which was inherently valuable in Islam because of its ability to determine the astronomically defined prayer times and to find the direction to Mecca. Many of the astrolabes became elegant works of art, with stylistic differences in the various Muslim regions.
The astrolabe was introduced to Europe through North Africa and Spain (al-Andalus) as early as the eleventh century although its use was not widespread until the thirteenth century, with peak usage in the fifteenth and sixteenth centuries. Latin names were engraved alongside the Arabic words on the astrolabes; it seems likely that the use of Arabic star names in Europe was influenced by the importing of these instruments.
There were two main types: the mariner’s astrolabe used for navigation – to determine the altitudes of the sun and starts; the planispheric astrolabe, the most common instrument, was used for astrological purposes. Initially consisting of six parts including the latitude plate which was made for specific latitudes, Ibrahim al-Zarqali (d. 1987), known as Azarchel in the West, introduced a universal plate capable of calculations at any latitude, thereby rendering the astrolabe usable in any part of the world – it did not need electricity, batteries or WiFi! The compact versatile nature of the astrolabe made it the most treasured instrument for astronomers.The use of the astrolabe declined in the late seventeenth century with the invention of the pendulum clock and the telescope.
The Aga Khan Museum has in its collection a planispheric astrolabe dated 1300s, bearing the names of constellations in both Arabic and Latin.
*Richard Covington, The Astrolabe: A User’s Guide, Saudi Aramco World
Robert A. Agler, Measuring the Heavens: Astronomical Instruments before the Telescope, The Smithsonian Astrophysical Observatory
Research by Nimira Dewji
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