Rose Mirror, 1844-66.
© Science Museum / Science & Society Picture Library
William Parsons, 3rd Earl of Rose (1800-1867), built a series of telescopes at Birr Castle, his home in Ireland. He was interested in the construction of large reflecting telescopes, and after casting several three foot diameter metal mirrors he decided to make one six feet acros. This mirror weighing over four tonnes is the only surviving example of the five mirrors that Lord Rose cast between 1842-45. The resulting reflecting telescope, known as the 'Leviathan of Parsonstown' had a tube 15m long suspended between masive masonry walls. Rose used this great telescope to try and determine the nature of nebulae. He was the first to discover that some had spiral forms, now known to be remote islands of stars like our own Milky Way Galaxy.