Astrolabe The astrolabe was a multifunctional calculating instrument invented around 200 BC by the Greek astronomer Hipparchus (who devised a plane astrolabe). It could be used as a sundial, a nocturnal, a surveying instrument or a calendar and was particularly useful for facilitating astrological readings and making astronomical measurements. It was also used in navigation for calculating latitude. To account for the fact that the positions of celestial bodies vary according to the observer’s location on Earth, astrolabes usually came with a series of plates associated with the different latitudes of large cities. The technique used to map the celestial sphere onto the two-dimensional flat plates of an astrolabe is called stereographic or planespheric projection. You can read more about the history of the astrolabe and how it was used in the Clocktime article The First Timekeepers: Telling time before the pendulum clock. Further Reading Huth, J. E. 2015. The Lost Art of Finding Our Way. Cambridge, MA, and London: Harvard University Press. Plassmeyer, P. 2019. ‘Scientific instruments as courtly objects’ in Koeppe, W. (editor) Making Marvels: Science and splendour at the courts of Europe. New York, NY: Metropolitan Museum of Art; New Haven, CT, and London: Yale University Press, pp. 113–120. Neugebauer, O. 1949. Isis, pp. 240–256 (for the plane astrolabe). Poppick, L. 31 January 2017. ‘The story of the astrolabe, the original smart phone’ in Smithsonian Magazine. Toomer, G. J. and A. Jones. March 2016. Oxford Classical Dictionary online, entry ‘astronomical instruments’. Turner, A. J. 1985. The Time Museum, Volume 1, Time Measuring Instruments: Astrolabes, astrolabe-related instruments. Wilmington, DE: Rockford, pp. 128–131. Turner, A. J. 1987. Early Scientific Instruments: Europe 1400–. London: Sotheby’s Publications, pp. 39–40.
