Astrolabe

An astrolabe (Greek: ἀστρολάβος astrolabos, "star-taker") is an elaborate inclinometer, historically used by astronomers and navigators, to measure the inclined position in the sky of a celestial body, day or night. It can thus 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 Islamic Golden Age, the European Middle Ages and the Renaissance for all these purposes.

While the astrolabe is effective for determining latitude on land or calm seas, it is less reliable on the heaving deck of a ship in rough seas. The mariner's astrolabe was developed to solve that problem.

OED gives the translation "star-taker" for the English word "astrolabe" and traces it, through medieval Latin, to the Greek word astrolabos from astron "star" and lambanein "to take". In the medieval Islamic world the word "asturlab" (i.e. astrolabe) was given various etymologies. In Arabic texts, the word is translated as "akhdh al-kawakib" (lit. "taking the stars") which corresponds to an interpretation of the Greek word.Al-Biruni quotes and criticizes the medieval scientist Hamzah al-Isfahani who had stated: "asturlab is an arabization of this Persian phrase" (sitara yab, meaning "taker of the stars"). In medieval Islamic sources, there is also a "fictional" and popular etymology of the words as "lines of lab". In this popular etymology, "Lab" is a certain son of Idris (=Enoch). This etymology is mentioned by a 10th-century scientist named al-Qummi but rejected by al-Khwarizmi. "Lab" in Arabic also means "sun" and "black stony places" (cf. Dictionary).

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