Ellison, William Frederick Archdall (1864–1936), clergyman and astronomer, was born 28 April 1864 in Thomastown, Co. Kilkenny, eldest among eight sons and three daughters of the Very Rev. Humphrey Eakin Ellison of Shillelagh, Co. Wicklow, dean of Ferns, and Letitia Ellison (née Archdall) of Farm Hill, Co. Wexford. William was educated by his father and entered TCD in 1883 with a sizarship in classics. He graduated with junior moderatorships in classics and experimental science in 1887. He took holy orders in 1890 and held two curacies in Co. Durham. In 1894 he took his MA and BD degrees, and was awarded the Elrington theological prize the following year.
He returned to Ireland in 1899 to become secretary of the Sunday School Society, and in 1902 incumbent of Monart, Enniscorthy, Co. Wexford. Six years later he was appointed rector of Fethard-on-Sea with Tintern in Wexford, where he set up his first astronomical observatory and began grinding and polishing mirrors and lenses, in which he was very skilful. Taking advantage of the invention of carborundum (silicon carbide), which became available in 1900, thus greatly reducing the labour of grinding, he established a wide reputation for excellent optics and published articles on telescope making in the English Mechanic.
In 1918 Ellison was appointed director of Armagh observatory. He added to its equipment his 18-in. (45 cm) reflector made by George Calver and a 6-in. (15 cm) refractor. He made planetary observations and, with the assistance of his youngest son Mervyn, undertook a programme to measure double stars. In 1920 he published his collected articles from the English Mechanic as a practical handbook, The amateur's telescope. According to Russell G. Porter, Ellison's book was the only modern handbook on telescope making available at the time, and it was incorporated into the famous three-volume work Amateur telescope making, edited by Albert G. Ingalls and published by Scientific American in 1933. Ellison was elected MRIA in 1932, and died 31 December 1936.
He married first (1891) Elizabeth Havelock Blackburn (d. 1934), daughter of Joseph J. G. Blackburn of Co. Durham. They had three sons, the eldest of whom was killed in the first world war. He married secondly (20 October 1934) Kathleen, daughter of the late F. R. Sproule of Dublin. His youngest son, Mervyn Archdall Ellison (1909–62), astronomer, was born 5 May 1909 at Fethard-on-Sea, Co. Wexford, and was 9 years old when his father became director of Armagh observatory. While attending Armagh Royal School, he was taught practical astronomy by his father and he had access to the observatory's telescopes. At the age of 13 he was making detailed drawings of sunspots and by 16 he had a paper on double stars accepted for publication. In 1927 he won a sizarship to TCD and studied physics. He graduated in 1931 with a moderatorship in experimental science and a gold medal; he received an M.Sc. in 1932. He taught for one year at Armagh Royal School and then went to Sherbourne School, Dorset (1933), as senior science master.
At Sherbourne Ellison constructed his own spectrohelioscope after the design of G. E. Hale, grinding his own mirrors and lenses. This instrument allowed him to study solar features such as prominences and flares. During the second world war he served in the operational research group of the admiralty, under Prof. P. M. S. Blackett. When he returned to Sherbourne, a very high sunspot maximum was in progress and he obtained some superb observations, including a great flare over a giant sunspot in July 1946.
Ellison's professional career began in 1947 with his appointment as principal scientific officer and deputy director at the Royal Observatory, Edinburgh. His spectrohelioscope was remounted at Edinburgh so he could continue his solar research. His chief aim was to record the change of flare intensity with time. He used long-wave radio receivers to record ionospheric disturbances and to correlate these with solar activity. The results of his research over eleven years in Edinburgh appeared in the Publications of the Royal Observatory and in the Monthly Notices of the Royal Astronomical Society. He was joint editor of The Observatory for five years, and his popular book The sun and its influence was published in 1955.
In 1952 Ellison joined the UK national committee for the International Geophysical Year (IGY) as representative for solar activity. From 1955 he was a member of the committee for the study of solar-terrestrial relationships under the International Council of Scientific Unions. Later he was appointed World Reporter for Solar Activity of the IGY, which began in July 1958. As part of the British contribution to the IGY, Ellison went to South Africa early in 1958 and installed an automatic solar telescope at the Royal Observatory, Cape of Good Hope. This heliograph took 35-mm photographs of the full disk of the sun in hydrogen light at one-minute intervals.
In November 1958 Ellison was appointed senior professor in the School of Cosmic Physics of the Dublin Institute for Advanced Studies and took up residence at Dunsink observatory. Over the next five years the Cape solar photographs were sent to Dunsink for analysis and the results appeared in Dunsink Observatory Publications. With the conclusion of the IGY, Ellison had the onerous task of organising the publication of daily solar charts showing every significant feature. This great work appeared as volumes 21 and 22 of the Annals of the International Geophysical Year.
Mervyn Ellison received the degree of Sc.D. from Dublin University (1944) and was elected a fellow of the Royal Society of Edinburgh in 1948. He was elected a fellow of the Royal Astronomical Society in 1938 and served on its council from 1940 to 1950. He died 12 September 1962, aged only 53.
He married (1934) Patricia, only daughter of Crosthwaite Heron, MD, of Armagh. He was survived by his wife, two daughters, and a son.