Markree Observatory was an astronomical observatory in County Sligo, Ireland. The asteroid 9 Metis was discovered from this observatory in 1848 by Cooper's assistant Andrew Graham using a comet seeker telescope. The observatory was also home to the largest refractor of the early 1830s, which had a aperture Cauchoix of Paris lens; the largest in the world at that time. The observatory also housed a number of instruments and was operated to varying degrees throughout the 19th century. The observatory is noted for its discovery of the asteroid 9 Metis in 1848 as well as a 60,000 item star catalogue of the 1850s. In the later 1800s it was operated again after a brief hiatus, and gained note for its meteorological observations and research on double stars. History In 1830, Colonel Edward Joshua Cooper MP (1798–1863) eldest son of Edward Synge Cooper MP, and Ann, daughter of Henry Vansittart, Governor of Bengal, set up Markree Observatory on the grounds of Markree Castle near Collooney in County Sligo. In 1831 Cooper acquired from Robert A. Cauchoix of Paris an objective of 13.3-inches (~33.78 cm) for which he paid £1200. In 1834 he mounted the lens on an equatorial mounting supplied by Thomas Grubb of Dublin. For a number of years Cooper's big refractor was the largest in the world. He used the telescope to sketch Halley's comet in 1835 and to view the solar eclipse of 15 May 1836. Later a 5-foot (1.5m) transit and a 3-foot (0.9m) meridian circle, fitted with an interchangeable 7-inch (17.75 cm) glass were added, which was the largest at that time in 1839; also in 1842 a 3-inch comet seeker was added. The observatory had a Stevenson screen, invented in 1863. "The Observatory of Mr Cooper of Markree Castleundoubtedly the most richly furnished private observatory knownis worked with great activity by Mr Cooper himself and by his very able assistant, Mr Andrew Graham." (Royal Astronomical Society, 1851) In 1848, Cooper's assistant, Andrew Graham, discovered the asteroid 9 Metis with a wide-field comet seeker telescope manufactured by Ertel. Graham resigned his post at Markree in 1860, but continued his research at Cambridge Observatory until his retirement in 1905. E.J. Cooper died in 1863, but the observatory remained active until the death of Edward Henry Cooper MP in 1902. The 13+ inch Cauchoix The Cauchoix telescope was installed inside a circular wall, but it had no dome