Groombridge's Catalogue: new reductions

Between 1806 and 1816 Stephen Groombridge (a trader and retailer but also a skilful and highly respected amateur astronomer, 1755-1832), undertook 50,000 observations of more than 4000 stars brighter than magnitude 8.5 between the north celestial pole and declination +38 degrees from his home observatory in Blackheath, London. His work in reducing these observations was curtailed by a partially paralysing stroke in 1827, but such was the regard for his work that the data was passed to the Royal Observatory for the completion of the reductions. The first publication of Groombridge's Catalogue in 1832 was speedily suppressed when serious errors made by the assistant Henry Taylor were discovered. A corrected edition for the epoch 1810, produced under close supervision of George Airy, was published in 1838 (a copy is at RGO 18/90) . The catalogue proved useful in the study of proper motions of stars and the dynamics of our galaxy.

By the late 1800s the Royal Observatory was heavily involved in an international project to photograph of regions of the sky to determine stellar positions for an International Astrographic Catalogue. On his appointment in 1894 as chief assistant at the Observatory, Frank Watson Dyson, began to oversee the Greenwich portion of the project. Dyson seems to have been spurred by this work to improve knowledge of stellar motions, and so with the assistance of, William Grasset Thackeray, he reobserved and revised the reductions of Stephen Groombridge's observations of circumpolar stars. With some new data this was published as a ''New reduction of Groombridge's circumpolar catalogue for the epoch 1810.0'', (Edinburgh; Neill & Co., 1905) (a copy is at RGO 18/599). The work confirmed Jacobus Cornelius Kapteyn's hypothesis that stars had preferred directions of motion in space.

Volumes /1-/42 are bound pages of reproduced manuscript forms designed to facilitate the re-reduction of Stephen Groombridge's observations by Dyson and Thackeray. Volumes /43-/61seem to be the product of Airy's earlier work and were probably placed into this sequence when used for reference by Dyson and Thackeray.

Produced or accumulated by the Royal Observatory, Greenwich.

Please cite as Royal Greenwich Observatory Archives, Groombridge's Catalogue: new reductions, RGO 128

Further material, especially correspondence relating to the Taylor and Airy reductions, may be found at : RGO 4/185; RGO 4/187/4; RGO 6/192; RGO 6/247; RGO 6/777; RGO 7/82/8-10; RGO 7/84; RGO 7/167; RGO 7/168; RGO 7/180; RGO 14/48; RGO 18/90; and RGO 18/599.

The online catalogue for Janus was compiled from an existing list in January 2010 by Zoe A. Rees, Department of Manuscripts and University Archives. The administrative history was compiled with reference to the online Dictionary of National Biography entries for Groombridge (http://www.oxforddnb.com/view/article/11655) and Dyson (http://www.oxforddnb.com/view/article/32949) (accessed January 2010).