astrolabe
Sign in to savealt=Planispheric Astrolabe made of brass, cast, with fretwork rete and surface engraving|thumb|upright=1.2|North African, planispheric astrolabe. Khalili Collections|Khalili Collection. thumb|upright|A modern astrolabe made in 2013, in Tabriz, Iran.
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An astrolabe is a brass instrument with intricate fretwork and engraving, historically used for astronomical and navigational purposes. It remains culturally and scientifically significant as an example of sophisticated medieval craftsmanship, with artisans continuing to make them by hand in places like Iran today.
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Article
17 sectionsContents
- Applications
- Etymology
- History
- Ancient era
- Medieval era
- Astrolabes and clocks
- Construction
- Mathematical basis
- Designing a tympanum through stereographic projection
- The tropics and the equator define the tympanum
- The horizon and the measurement of altitude
- The meridians and the measurement of azimuth
- See also
- Footnotes
- References
- Bibliography
- External links
alt=Planispheric Astrolabe made of brass, cast, with fretwork rete and surface engraving|thumb|upright=1.2|North African, planispheric astrolabe. Khalili Collections|Khalili Collection. thumb|upright|A modern astrolabe made in 2013, in Tabriz, Iran.
An astrolabe (; ; ) is an astronomical instrument dating to ancient times. It serves as a star chart and physical model of the visible half-dome of the sky. Its various functions also make it an elaborate inclinometer and an analog calculation device capable of working out several kinds of problems in astronomy. In its simplest form it is a metal disc with a pattern of wires, cutouts, and perforations that allows a user to calculate astronomical positions precisely. It is able to measure the altitude above the horizon of a celestial body, day or night; it can be used to identify stars or planets, to determine local latitude given local time (and vice versa), to survey, or to triangulate. It was used in classical antiquity, the Byzantine Empire, the Islamic Golden Age, the European Middle Ages and the Age of Discovery for all these purposes.