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An instrument used to make astronomical measurements, typically of the altitudes of celestial bodies, and in navigation for calculating latitude, before the development of the sextant. In its basic form (known from classical times) it consists of a disc with the edge marked in degrees and a pivoted pointer. Recorded from late Middle English, the word comes ultimately (via Old French and medieval Latin) from Greek astrolabos ‘star-taking’.

Subjects: History

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