An Etymological Dictionary of Astronomy and Astrophysics
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A → transit circle that defines the position of the → Greenwich Meridian since the first observation was taken with it in 1851. Airy's transit circle lies at longitude 0°, by definition, and latitude 51° 28' 38'' N.

Named after Sir George Biddell Airy (1801-1892), Astronomer Royal, at the Royal Observatory in Greenwich from 1835 to 1881. Airy transformed the observatory, installing some of the most advanced astronomical apparatus of his day and expanded both staff numbers and their workload; → transit; → circle.

An observing instrument provided with a graduated vertical scale, used to measure the declinations of heavenly bodies and to determine the time of meridian transits. Same as → meridian circle.

→ transit; → circle; nimruzâni, adj. of nimruzân, → meridian.