Robert Lewis John Ellery CMG FRS FRAS (14 July 1827 – 14 January 1908) was an English-Australian astronomer and public servant who served as Victorian government astronomer for 42 years.

Ellery was born in Cranleigh, Surrey, England, the son of John Ellery, a surgeon, and his wife Caroline, née Potter. Ellery was educated at the local grammar school and qualified as a medical practitioner working as a surgeon in London until 1851. Ellery developed an early interest in practical astronomy and meteorology and sought relaxation from his medical studies in those branches of science, occasionally working as an amateur at England's principal observatories.^[1] Friends at Greenwich Observatory encouraged him and he had some access to instruments there.

Ellery sailed for Victoria in 1851 aboard the Moselle, attracted by the discovery of gold and the opportunity to practice astronomy and meteorology. Upon arrival, Ellery established a medical practice from his residence at the top end of Bourke Street, Melbourne, Victoria. In 1853 the Victorian government invited him to establish and manage an observatory at Gellibrand's Point (now Williamstown), Victoria, appointing him as Superintendent for the purposes of commercial astronomy.^[1] Ellery's key duty was to determine precise local mean time for the masters of vessels to correct their chronometers in Hobson's Bay, which by that time had become rapidly crowded with shipping [due to the Victorian Gold Rush].^[2] The astronomical observatory^[3] provided a service to shipping, whose navigators relied critically on accurate astronomical time for determination of their longitude and appreciated the opportunity to synchronise their chronometers. Ellery had already established a reputation as an astronomer and in July 1853 was put in charge of the facility.^[4] The Victorian government observatory was at first on a very modest scale, being housed in a small two-roomed cottage at Williamstown, and the only instruments were a sextant, an artificial horizon and a marine chronometer. However, by March 1854, a 30-inch transit instrument, a good astronomical clock and a time-ball apparatus had been added, and a few meteorological instruments were also obtained.

When the Williamstown and Melbourne telegraph lines was erected in 1854, the Williamstown end was also placed under Ellery's charge.^[1] Ellery's workload was not heavy, and he also undertook for a time the duties of storekeeper of the marine depot.

In 1856 Ellery began a geodetic survey of Victoria which was not completed until 1874. In 1858, he was appointed to be a Land Surveyor in the Victorian Government Department of Public Lands, in addition to his duties as Superintendent of the Astronomical Observatory at Gellibrand's Point.^[5] He was further appointed to Superintend the geodetic survey of Victoria by the Surveyor General of Victoria Charles Whybrow Ligar.^[1]

In 1863 Ellery was appointed to the Board of Examiners for the Department of Lands and Survey.^[6]

At the beginning of 1858 the government founded a magnetic observatory on Flagstaff Hill, West Melbourne, under a distinguished German scientist, Georg von Neumayer, who had applied for a site in the Domain south of the Yarra without success. Both Ellery and Neumayer found that the sites given them were not suitable for their work, but it was not until 1863 that a move was made to the Domain. Edward John White, an able astronomer, was added to Ellery's staff in May 1860, and several valuable catalogues of stars were prepared and published. Melbourne Observatory played a crucial role in the 1862 determination of the distance from the earth of the sun, which involved close cooperation between Ellery and E. J. Stone of Greenwich.^[7]

In 1868 a new telescope was sent out from England but the results obtained with it were unsatisfactory. Ellery resolved the issues he had with the telescope by applying his mechanical ability to the problems involved.^[vague] Ellery had an able assistant in Ebenezer Farie Macgeorge (born 1836), who had been his surveyor in 1867 when he defined the boundary between South Australia and New South Wales, then replaced Albert Le Sueur as his observer, serving from 1870 to 1872. In March 1871 he reported to the Royal Society of Victoria that since Le Sueur's polishing of the Great Melbourne Telescope the chief limitation to observation was the atmosphere, not the instrument.^[8]

At the end of 1890, another telescope arrived and Ellery began a new important piece of work, the preparation of the share allotted to Melbourne of the astrographic chart. He retired in 1895 and was succeeded by Pietro Baracchi.

Ellery was a founding member of The Institution of Surveyors Victoria established in 1874,^[9] and served as its first President (1874-1877), after Surveyor General Alexander John Skene declined the office due to pressure of public business.^[10] He was elected Fellow of the Victorian Institute of Surveyors in 1877, the first to be awarded the honour.^[11]

In addition to his own work Ellery had much to do with educational and scientific bodies. He was one of the founders of the Royal Society of Victoria and its president from 1866 to 1884, became a trustee of the public library, museums and National Gallery of Victoria in 1882, and was also for many years a member of the council of the University of Melbourne.

He was interested in the volunteer movement and in 1873 organized the Victorian torpedo corps, afterwards the submarine mining engineers. He was in command until 1889, when he retired with the rank of lieutenant colonel. In 1900, Ellery was elected president of the Australasian Association for the Advancement of Science; he chose as the subject of his address "A Brief History of the Beginnings and Growth of Astronomy in Australasia". Ellery a keen apiarist and was the first president of the Victorian Beekeepers' Club in 1885, and edited the Australian Beekeepers' Journal.

Early in 1907 Ellery had a paralytic stroke, but recovered well and was in fair health until shortly before his death at Melbourne on 14 January 1908. Ellery wrote many papers for scientific journals some of which were re-issued as pamphlets. Some of the catalogues of stars and other work done under his supervision at the observatory were published, but at the time of his death much remained in manuscript. He was elected a fellow of the Royal Society, London, in 1873, and was created C.M.G. in 1889. He was married twice, to two sisters, daughters of Dr John Shields. He left a widow and a daughter.

Ellery was awarded the Clarke Medal by the Royal Society of New South Wales in 1889. Mount Ellery in Antarctica was named after him in 1886.