Arthur William Long, amateur astronomer, came to South Africa around 1900. He was soon employed by Messrs W.M. Cuthbert, boot manufacturers, and remained associated with that firm for his entire career. He was stationed in Beaufort West and travelled mainly in the Karoo for his work. His interest in astronomy was intensified by the return of Halley's comet in 1910. Subsequently he became one of the group of persons who initiated the establishment of the Cape Astronomical Association in Cape Town in 1912. He served as a member of its council from the beginning, was joint vice-president in 1916, and president in 1921. Council meetings were often held at his home and during World War I (1914-1918) the revival of the association was largely the result of his efforts. He purchased a 75 mm refracting telescope with which he made observations at his home. For a period of 25 years from 1913 he prepared monthly star charts that were published in the Cape Times and circulated throughout South Africa, thus making an important contribution to the spreading of astronomical knowledge among the South African public.
When the Cape Astronomical Association amalgamated with the Johannesburg Astronomical Association in 1922 to form the Astronomical Society of South Africa Long served on the council of the latter until his death, was elected president for 1928/9 and joint vice-president for 1929/30, 1935/6 and 1937/8. In his inaugural address as president he presented a detailed account of 'The foundation and development of the Astronomical Society of South Africa', which was published in the society's Journal (1930, Vol. 2(4), pp. 153-180). He also served on the editorial committee of the society's Journal and did part of the editorial work. He was furthermore a prominent member of the society's Variable Star Section and contributed over 4000 observations to its records. Throughout the existence of the association and the society he was the intermediary between the Royal Observatory, Cape of Good Hope, and amateur observers in South Africa. From 1917 he and other prominent amateurs, including J.F. Skjellerup*, were allowed to use a 150 mm equatorial refracting telescope at the observatory for visual estimates of the brightness of variable stars.
Long was elected a Fellow of the Royal Astronomical Society (FRAS) in January 1921. In 1929 he was one of the representatives of the Astronomical Society of South Africa on the South African National Committee on Astronomy. His star atlas for southern latitudes, The constellations as seen from South Africa on any night in the year (Cape Astronomical Association, 1922) was a standard work of which subsequent editions appeared in 1923 and 1944. He also contributed various papers to the publications of the Cape association and astronomical society: Papers on Saturn (1918) and Formulae for rising and setting of the sun and moon (1921/2), both published by the Cape Astronomical Association; and articles on 'Observations of the new moon' (with T. MacKenzie*, 1923), 'The sky in May' (1924), and 'Jupiter' (1925) in the Journal of the Astronomical Society of South Africa.
Long suffered a stroke in August 1938 and died the next year.