Astrolabe

<p>An astrolabe  is an <a href="/facts/Astronomy/0ArJVM1p">astronomical</a> <a href="/facts/List_of_astronomical_instruments/1KCmcxRW">instrument</a> dating to ancient times. It serves as a <a href="/facts/Star_chart/nKY9u81I">star chart</a> and <a href="/facts/Model/Hj8KMwdD">physical model</a> of the visible <a href="/facts/Celestial_sphere/TYAtXgor">half-dome of the sky</a>. Its various functions also make it an elaborate <a href="/facts/Inclinometer/NB4nFvg5">inclinometer</a> and an <a href="/facts/Analog_computer/3NhYoCML">analog calculation device</a> 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 <a href="/facts/Horizontal_coordinate_system/msJQPYg0">altitude</a> above the horizon of a celestial body, day or night; it can be used to identify stars or planets, to determine local <a href="/facts/Latitude/IBYqkjhU">latitude</a> given <a href="/facts/Local_time/8y4NTspE">local time</a> (and vice versa), to survey, or to <a href="/facts/Triangulation/lpmlmhGd">triangulate</a>. It was used in <a href="/facts/Classical_antiquity/JBq8vEX9">classical antiquity</a>, the <a href="/facts/Islamic_Golden_Age/yAeG2rBA">Islamic Golden Age</a>, the European <a href="/facts/Middle_Ages/RqzEKB9v">Middle Ages</a> and the <a href="/facts/Age_of_Discovery/Hy29CbgV">Age of Discovery</a> for all these purposes.
</p><p>The astrolabe, which is a precursor to the <a href="/facts/Sextant/KYjC81QE">sextant</a>,
is effective for determining latitude on land or calm seas. Although it is less reliable on the heaving deck of a ship in rough seas, the <a href="/facts/Mariner%2527s_astrolabe/Lg4qjd1Q">mariner's astrolabe</a> was developed to solve that problem.
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Astrolabe open-in-new

Astrolabe