[1][2] Sisson worked at a time when demand from the Royal Observatory, Greenwich and the Ordnance Survey, and assistance from the Royal Society, had brought London instrument makers to a dominant position in supply of the technically demanding work of making instruments for astronomy, survey and navigation.

[1] According to Jean Bernoulli, among the London instrument makers in 1769 Sisson ranked after John Bird but ahead of Ramsden in his skill.

[12] Prince Carl Theodor, Elector Palatine, set up an observatory of the roof of his castle at Schwetzingen in 1764, directed by Christian Mayer (1719-1783).

Meyer wanted to buy other instruments in 1782, but Sisson was busy with other work and only agreed to make a 6 feet (1.8 m) transit.

On 21 March 1783 Meyer received a contract for the transit, countersigned by Maskelyn and the astronomer Thomas Hornsby of Oxford, to be made and delivered for 145 1⁄2 guineas.