Cooper, Edward Joshua (1798–1863), astronomer and MP, was born in May 1798 at St Stephen's Green, Dublin, the eldest son of Edward Synge Cooper (1762–1830) of Markree castle, Co. Sligo, landowner and MP for Co. Sligo (1806–30), and his wife Anne, daughter of Henry Verelst, governor of Bengal. He was educated at the endowed school at Armagh, Eton and Christ Church, Oxford. He left Christ Church after two years without taking a degree and spent the next few years travelling very widely in Europe, Persia and Egypt, taking portable astronomy instruments with him, and determining the geographical positions of many places. A book on his travels in Egypt in 1820–1, illustrated by an Italian artist, was printed for private circulation in 1824. After extensive travels in Europe and north Africa he settled on Nice and Munich as the most suitable observation locations encountered.
On his father's death in 1830, Cooper returned to the family estate at Markree Castle, Co. Sligo, as agent for his uncle Joshua; on this uncle's death in 1837, Edward inherited over thirty thousand acres in counties Sligo and Limerick and became a very wealthy man. He had begun meteorological readings at Markree in 1824 and in 1830 set about establishing an astronomical observatory there. In the following year he purchased in Paris an objective of 13.5 inches (35.5cm), the largest that had been built to that date. Its wooden stand was replaced in 1834 by Thomas Grubb (qv) with an equatorial mounting, which for the first time made use of cast iron in the tube and stand. Cooper assembled a number of other instruments on the site, and developed what was described in the Monthly Notices of the Royal Astronomical Society in 1851 as ‘the most richly furnished of private observatories in the world’, though the telescope was set up in the open air. Members of the British Association visited it in 1835. Cooper sketched Halley's Comet in 1835 and on 25 April 1848, his assistant, Andrew Graham (1815–1907), discovered a minor planet or large asteroid, Metis, the first ever recorded as a result of observations from Ireland. From 1848, Cooper and Graham worked together on observations designed to facilitate the discovery of distant and faint planets, and charted the approximate positions and magnitudes of over 60,000 stars, almost all previously unobserved. Much of the enormous amount of work was carried out by Graham. The ambitious and extensive Catalogue of stars near the ecliptic observed at Markree was published at government expense in four volumes from 1851–6. Cooper also published a useful compilation, Cometic orbits, with copious notes and addenda (1852).
Cooper was elected MRIA (1832) and FRS (1853), and in 1858 received the Cunningham Medal from the RIA for his catalogue. He was conservative MP for Co. Sligo (1830–41 and 1857–9), and was an improving and popular landlord. At considerable expense, he maintained a trades school at Collooney for the benefit of his tenants, and his wife established several elementary schools locally. Cooper also organised and supported a Farming Society, helped improve the quality of livestock in the county, and had acts of parliament passed to enable him to set up the first salmon ladders in Ireland, for a salmon fishery on the Ballisodare river.
Edward Cooper married twice. His first wife was Sophia L'Estrange, daughter of Henry Peisley L'Estrange, of Moystown, King's Co. They are said to have married 1 January 1822. Sophia died in 1823, giving birth to a son, who also died. Cooper and his second wife, Sarah Frances, daughter of Owen Wynne of Hazelwood, Co. Sligo, had five daughters. Cooper died 23 April 1863 at Markree Castle and was buried at Ballisodare, Co. Sligo.