Groombridge Transit Circle

Groombridge Transit Circle was a meridian transit circle made by Edward Troughton for the English astronomer Stephen Groombridge in 1806, which Groombridge used to compile data for the star catalogue, Catalogue of Circumpolar Stars.

[1] The advantage of a transit circle over a mural circle (which can measure polar distances) is that it allows measuring right ascension and declination at the same time.

[2] It had an aperture of 3.5 inches and a 5-foot focal length, mounted inside two 4 foot circles on stone piers.

[2] Groombridge used the instrument to determine the positions of over 4000 circumpolar stars.

[2] It was eventually bought by James South, and it remained at his observatory at Kensington until 1870.