Groombridge Transit Circle
Encyclopedia
Edward Troughton
Edward Troughton FRS was a British instrument maker who was notable for making telescopes and other astronomical instruments.Troughton was born at Corney, Cumberland...
for Stephen Groombridge
Stephen Groombridge
Stephen Groombridge FRS was a British astronomer.In 1806, using a then new transit circle built by Edward Troughton, he began compiling a star catalogue of stars down to about eighth or ninth magnitude...
in 1806, which Groombridge used to compile data for the star catalogue
Star catalogue
A star catalogue, or star catalog, is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some...
, Catalogue of Circumpolar Stars. 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.
It had an aperture of 3.5 inches and a 5 foot focal length, mounted inside two 4 foot circles on stone piers. Groombridge used the instrument to determine the positions of over 4000 circumpolar stars.
It was eventually bought by James South
James South
Sir James South was a British astronomer.He helped found the Astronomical Society of London, and it was under his name as president of the society from 1831 to 1832 that a petition was successfully submitted to obtain a royal charter in 1831, whereupon it became the Royal Astronomical...
, and it remained at his observatory at Kensington until 1870.