Airy's altazimuth instrument. This equipment was constructed in 1847 by the seventh Astronomer Royal, Sir George Biddell Airy (1801-1892). The instrument was a telescope mount that moved in a transit circle and could be turned to observe astronomical objects at any azimuth and altitude. It was housed by the Royal Observatory at Greenwich and was used by Airy to accurately observe the positions of the moon. This altazimuth was replaced in the late 19th century by a larger one and it was eventually donated to the Science Museum in 1910.