Airy's transit circle.

Repro ID: D7064_1

Description: Constructing Airy's huge transit circle was a major undertaking. The engineering was carried out by Ransomes and May of Ipswich & Troughton and Sims constructed both the optical parts (including the 8 1/8 in./20.6 cm object lens) and the main body. But the instrument was designed almost wholly by Airy himself. As the transit circle was not wall-mounted, repeated use often meant that the telescope fell out of true vertical alignment. To remedy this it was realigned (or collimated) weekly. From 1854 a recording apparatus, or chronograph, was introduced to record its observations on a rolling drum of graph paper

Creator: Troughton and Simms; Ransomes and May

Date: 1851

Credit line: National Maritime Museum, London