Leviathan of Birr. This is the 6-foot telescope (the Leviathan of Birr), at Birr Castle, Parsonstown, Ireland. This telescope was constructed in 1845 by the Irish astronomer William Parsons (1800-1867), the 3rd Earl of Rosse. Pioneering research carried out with this telescope includes the observation of the spiral structure of the M51 galaxy (1845). The telescope was the largest in the world during its lifetime, and was moved up and down between supporting walls and accessed by ladders. The 6-foot mirror and telescope was dismantled in 1908, and the support structures demolished in 1925. A replica was constructed in the 1990s, and the site is now a museum.