Groombridge Transit Circle
From Infogalactic: the planetary knowledge core
File:Groombridge transit circle.jpg
Groombridge transit circle
Groombridge Transit Circle was a meridian transit circle made by Edward Troughton for 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]
References
- ↑ Groombridge Transit Circle, 1820. -- Science and Society Picture Library
- ↑ 2.0 2.1 2.2 2.3 King, Henry C., (1955/2003). The History of the Telescope. Cambridge, Massachusetts: Sky Publishing Corporation. Retrieved from Google Books in 2010: The History of the Telescope, by Henry C. King, page 234-6
