Groombridge Transit Circle was a meridian transit circle made by

Edward Troughton Edward Troughton FRS FRSE FAS (October 1753 – 12 June 1835) was a British instrument maker who was notable for making telescopes and other astronomical instruments. Life Troughton was born at Corney, Cumberland, the youngest of six child ...

for the English astronomer

Stephen Groombridge Stephen Groombridge FRS (7 January 1755 – 30 March 1832) was a British merchant and astronomer. Life He was born at Goudhurst in Kent on 7 January 1755. He succeeded when about 21 to the business in West Smithfield of a linen draper named ...

in 1806, which Groombridge used to compile data for the

star catalogue A star catalogue 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, ...

, ''Catalogue of Circumpolar Stars''.Groombridge Transit Circle, 1820. -- Science and Society Picture Library
/ref> The advantage of a

transit circle The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes mo ...

over a

mural circle A mural is any piece of graphic artwork that is painted or applied directly to a wall, ceiling or other permanent substrate. Mural techniques include fresco, mosaic, graffiti and marouflage. Word mural in art The word ''mural'' is a Spanish ...

(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 A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest po ...

. It was eventually bought by

James South Sir James South FRS FRSE PRAS FLS LLD (October 1785 – 19 October 1867) was a British astronomer. He was a joint founder of the Astronomical Society of London, and it was under his name, as President of the Society in 1831, that a petiti ...

, and it remained at his observatory at Kensington until 1870.

See also

References

Further reading