[as-truh-leyb] 
| an astronomical instrument for taking the altitude of the sun or stars and for the solution of other problems in astronomy and navigation: used by Greek astronomers from about 200 b.c. and by Arab astronomers from the Middle Ages until superseded by the sextant. |
[as-truh-lab-i-kuhl, -ley-bi-] , adjective | astrolabe (ās'trə-lāb') Pronunciation Key
An ancient instrument used widely in medieval times by navigators and astronomers to determine latitude, longitude, and time of day. The device employed a disk with 360 degrees marked on its circumference. Users took readings from an indicator that pivoted around the center of the suspended device like the hand of a clock. The astrolabe was replaced by the sextant in the 18th century. |