Crommelin, Andrew Claude de la Cherois (1865–1939), astronomer, was born 6 February 1865 at Cushendun, Co. Antrim, grandson of Nicholas Crommelin (qv), and third son among twelve children of Nicholas Crommelin and Annie Crommelin (née Mulholland) of Cushendun; his uncle John Mulholland became Lord Dunleath, and his sister Constance was a gifted mathematician, who taught at Roedean, Sussex, till her marriage to the poet John Masefield. Andrew Crommelin moved to England with the family when he was 3. He attended Marlborough College and graduated BA (1886) from Trinity College, Cambridge. His first intention was to become an anglican clergyman, but after a period when he was ‘unsettled in his religious convictions’ (Monthly Notices), he entered the Roman Catholic church (1891). After two years as a schoolmaster, he was appointed to the post of assistant in Greenwich observatory (1891) and spent the rest of his career there as an observer and computer. He was particularly interested in the orbits of comets: in 1907–8 he and a collaborator traced almost every appearance of Halley's comet from the first record in 240 BC, and were awarded the Lindemann prize of the Astronomische Gesellschaft and honorary D.Sc. degrees from Oxford University for their accuracy in calculating the date of the comet's perihelion: they predicted its 1910 return to within three days. Their method was applied successfully to other long-period astronomical bodies. Crommelin published very many useful papers and short notes, in particular, the Monthly Notices of the Royal Astronomical Society from 1898 to 1906 published his calculations of the ephemerides of the moon, Mars, Jupiter, and Saturn, and for over forty years he published monthly notes on the minor planets, dealing also with comets from 1916 to 1937. He took part in expeditions to observe solar eclipses in 1896, 1900, and 1905, and in 1919 photographed the solar eclipse in Brazil; his work was used as evidence of part of the theory of relativity. Crommelin was president of the British Astronomical Association 1904–5, and of the Royal Astronomical Society 1929–31. He continued to publish astronomical papers even after retiring from Greenwich (1927), and died in London 20 September 1939. He married (1897) Letitia Noble (d. 1921), a clergyman's daughter. One of their three sons became a priest; two others were killed in a climbing accident; there was also a daughter.
Monthly Notices of the Royal Astronomical Society, c (1940), 234–6; WWW; Dictionary of scientific biography; iii (1971), 472–3; C. E. B. Brett, Five big houses of Cushendun and some literary associations (1997), 56