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.[2]
- ^ Groombridge Transit Circle, 1820. -- Science and Society Picture Library
- ^ a b c d King, Henry C. (2003). The History of the Telescope. Cambridge, Massachusetts: Courier Corporation. pp. 234–6. ISBN 978-0-486-43265-6.