Airy's transit circle

Constructing Airy's huge transit circle was a major undertaking. The engineering was carried out by Ransomes & May of Ipswich and Troughton & Sims constructed both the optical parts (including the 206 mm 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 (or collimated) weekly. From 1854, a recording apparatus, or chronograph, was introduced to record its observations on a rolling drum of graph paper.

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