Ptolemy's version was a derivative of the astrolabe and the purpose of this rudimentary device was to measure the meridian angle of the sun. This quadrant was unlike later versions of the instrument it was larger and consisted of several moving parts. He described a "plinth" that could measure the altitude of the noon sun by projecting the shadow of a peg on a graduated arc of 90 degrees. Įarly accounts of a quadrant also come from Ptolemy's Almagest around AD 150. The use of a Tureeyam for observing a solar eclipse by Rishi Atri is described in the fifth mandala of the Rigveda, most likely between c. The quadrant condensed the workings of the astrolabe into an area one fourth the size of the astrolabe face it was essentially a quarter of an astrolabe.ĭuring Rigvedic times in ancient India, quadrants called 'Tureeyam's were used to measure the extent of a great solar eclipse. The term quadrant, meaning one fourth, refers to the fact that early versions of the instrument were derived from astrolabes. Mural quadrants were important astronomical instruments in 18th-century European observatories, establishing a use for positional astronomy. Several different variations of the instrument were later produced by medieval Muslim astronomers. It was then proposed by Ptolemy as a better kind of astrolabe. Its earliest recorded usage was in ancient India in Rigvedic times by Rishi Atri to observe a solar eclipse. Different versions of this instrument could be used to calculate various readings, such as longitude, latitude, and time of day. It was constructed in 1673.Ī quadrant is an instrument used to measure angles up to 90°. A large frame quadrant at the Beijing Ancient Observatory.
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