5.23.2013

Magnificent Computer of the Ancients: The Astrolabe

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Astrolabe @Museum of the History of Science, Oxford
      I frequently search for interesting topics, new designs, pictures and various kinds of information and yesterday I came across an ancient inclinometer which is called astrolabe. Here are some information about it.
      The name is derived from Greek astrolabos meaning "star-taker" and it is used by astronomers to predict the positions of the sun, moon, stars and the planets. These ancient computers are also used by navigators to show how the sky looks at a specific place at a given time and by astologers to cast horoscopes.   
       The system basicly consists of a deep disk holding one or more flat plates. These plates are made for specific latitudes and are engraved with stereographic projections of circles. The rim of the main disc is graduated into hours of time, degrees of arc or both. In order to use it, you just adjust the moveable parts to a specific date and time. After that, much of the sky, both visible and invisible, is represented on the instrument.  
       The history of the astrolabe begins more than 2000 years ago. An early one was invented in the Hellenistic world in 150 BC and is often attributed to Hipparchus. It seems to have been the most popular astronomical instrument until 1650s and then it was replaced by more accurate tools. Mechanical astronomical clocks (like Prague Orloj) were also influenced by the astrolabes. 
      If you are interested, the largest astrolabe collection in North America, and the best displayed in the world, is at the Adler Planetarium and Astronomy Museum in Chicago. Some other museums are: British Museum, Whipple Museum of the History of Science, Türk ve İslam Eserleri Müzesi and The Mariners' Museum.            
     
Prague Astronomical Clock (Prague Orloj)

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