Three foot Rosse telescope, Birr Castle, Ireland, 1880

Three foot Rosse telescope, Birr Castle, Ireland, 1880. A photograph of the Great Rosse reflecting telescope, taken from the east by Lieutenant Colonel Harry J Watson whilst he was posted to nearby Newbridge. Constructed in Parsonstown (now Birr) in Ireland by William Parsons, the Third Earl of Rosse (1800-1867), it was soon known as the 'Leviathan of Parsonstown'. The reflecting telescope - with its later equatorial mounting - used a six foot metal mirror weighing four tons. This was mounted in a 15 m tube slung by chains between massive masonry walls. Rosse used his great instrument to try and determine the nature of nebulae, misty patches in the sky. He was the first to discover that some had spiral forms, now known to be remote and massive islands of stars like our own Milky Way Galaxy. ©SSPL/Science Museum