Quadrant (instrument)

A large frame quadrant at the Beijing Ancient Observatory. It was constructed in 1673.

A quadrant is an instrument used to measure angles up to 90°. Different versions of this instrument could be used to calculate various readings, such as longitude, latitude, and time of day. Its earliest recorded usage was in ancient India in Rigvedic times by Rishi Atri to observe a solar eclipse.[1][2] It was then proposed by Ptolemy as a better kind of astrolabe.[3] Several different variations of the instrument were later produced by medieval Muslim astronomers. Mural quadrants were important astronomical instruments in 18th-century European observatories, establishing a use for positional astronomy.

  1. ^ Cite error: The named reference Rau was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference UoC was invoked but never defined (see the help page).
  3. ^ King, Henry C. (2003) [1955]. The History of the Telescope. Dover Publications. ISBN 978-0-486-43265-6.