David Gill (astronomer)
June 12, 1843|
|Died||January 24, 1914
Gold Medal of the Royal Astronomical Society
James Craig Watson Medal
Commandeur de la Légion d'honneur
Pour le Mérite
Sir David Gill FRS (12 June 1843 – 24 January 1914) was a Scottish astronomer who is known for measuring astronomical distances, for astrophotography, and for geodesy. He spent much of his career in South Africa.
Life and work 
David Gill was born in Aberdeen and educated at Dollar Academy. He spent two years at Aberdeen University, where he was taught by James Clerk Maxwell, and then joined his father's clock-making business. It would seem that Gill's interests lay elsewhere since after a few years he sold the business, and then spent time equipping Lord Lindsay's private observatory at Dun Echt, Aberdeenshire. In 1874, Gill joined the expedition to Mauritius to observe the transit of Venus. Three years later he went to Ascension Island to observe a near approach of Mars and to calculate its distance. While carrying out these laborious calculations, he was notified of his appointment to the Cape Observatory, which, over the following 27 years he was to refurbish completely, turning it into a first-rate institution. Gill was a meticulous observer and had a flair for getting the best out of his instruments. His solar parallax observations with a heliometer and his calculations of distances to the nearer stars, are testimony to his outstanding work. He recruited Robert Innes to the Cape Observatory.
Gill used the parallax of Mars to determine the distance to the Sun, and also measured distances to the stars. He perfected the use of the heliometer. He was Her Majesty's Astronomer at the Cape of Good Hope from 1879 to 1906. He was a pioneer in the use of astrophotography, making the first photograph of the Great Comet of 1882, and one of the early proponents of the Carte du Ciel project.
The invention of dry plate photography by Richard Leach Maddox made Gill realise that the process could be used to create images of the stars and to more easily determine their relative positions and brightness. This led to a massive project in collaboration with the Dutch astronomer J.C. Kapteyn, and the compiling of an index of brightness and position for some half a million southern stars. The work was published as Cape Photographic Durchmusterung in 3 volumes between 1896 and 1900. Gill also played a leading role in the organising of the Carte du Ciel, an ambitious international venture aimed at mapping the entire sky. He initiated the idea of a geodetic survey along the 30th east meridian stretching from South Africa to Norway, resulting in the longest meridian yet measured on Earth.
Gill married in 1870, and his wife accompanied him to Ascension Island for his Mars observations. On Gill's retirement in 1906, the couple moved to London, where Gill served for two years (1909–1911) as president of the Royal Astronomical Society before his death in 1914. He was buried in Aberdeen.
Selected writings 
His writings include memoirs on "Heliometer Determination of Stellar Parallax in the Southern Hemisphere" and "A Determination of the Solar Parallax and Mass of the Moon from Heliometer Observations of Victoria and Sappho" (in Annals of the Cape Observatory, volumes vi and vii, 1896). He also wrote A Determination of the Solar Parallax from Observations of Mars at the Island of Ascension (in the Memoirs of the Royal Astronomical Society, volumes xlvi and xlviii, 1881 and 1885). New International Encyclopedia In 1913 he published A History and Description of the Royal Observatory at the Cape of Good Hope.
- Elected Fellow of the Royal Society, 7 June 1883 
- Knighted, 24 May 1900
- President, Royal Astronomical Society, 1909–1911
- Member of the Royal Swedish Academy of Sciences, 1910
In 1909 he was invited to deliver the Royal Institution Christmas Lecture on Astronomy, Old and New.
- Bruce Medal (1900)
- Gold Medal of the Royal Astronomical Society (1882 and 1908)
- James Craig Watson Medal (1899)
Named after him 
- Jaff, Fay (1963). "David Gill - Watchmaker to Astronomer Royal". They Came to South Africa. Cape Town: H. Timmins. Retrieved 1 December 2010.
- Kapteyn, J. C. (1914). "Sir David Gill". The Astrophysical Journal 40: 161–171. Bibcode:1914ApJ....40..161K. doi:10.1086/142107. Retrieved 2008-05-17. Unknown parameter
- Davidson, M. (1933). "Anzeige des Todes von Robert Thorburn Ayton Innes". Astronomische Nachrichten (in German) 249: 51. Bibcode:1933AN....249...51D.
- "Gill's Work on the Determination of the Solar Parallax". Monthly Notes of the Astronomical Society of South Africa 2: 85–88. 1943. Bibcode:1943MNSSA...2...85.
- For her description of the expedition, see Gill, Isabel Sarah B. (1878). Six Months in Ascension: An Unscientific Account of a Scientific Expedition. London: John Murray.
- "Sir David Gill". The Observatory 37: 115–117. 1914. Bibcode:1914Obs....37..115. Retrieved 2008-05-17.
- "Library and Archive Catalogue". Royal Society. Retrieved 31 December 2010. Unknown parameter
- "James Craig Watson Medal". National Academy of Sciences. Retrieved 15 February 2011.
|Wikisource has original works written by or about:
- Gill, David. Heliometer observations for determination of stellar parallax made at the Royal Observatory, Cape of Good Hope (1893). Eyre and Spottiswoode. at the Internet Archive
- Bruce Medal page
- Awarding of Bruce Medal: PASP 12 (1900) 49
- Awarding of RAS gold medal, 1882: MNRAS 42 (1882) 216
- Awarding of RAS gold medal, 1908: MNRAS 68 (1908) 317
- Biographical sources