|Compare sextant an instrument used by early astronomers to measure the altitude of stars and planets and also as a navigational aid. It consists of a graduated circular disc with a movable sighting device|
|[C13: via Old French and Medieval Latin from Greek, from astrolabos (adj), literally: star-taking, from astron star + lambanein to take]|
|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.