The Leviathan of Parsonstown

Built at Birr Castle in the early 1840s by William Parsons, the third Earl of Rosse. The telescope was 72 feet long, with a mirror six feet across. From 1845 until 1914 it was the largest telescope in the world.

Its formal name was the Great Telescope. Everyone else called it the Leviathan of Parsonstown. With it, Rosse observed the spiral structure of the Whirlpool Nebula, now known to be a galaxy. Astronomers and visitors travelled from across Europe to Co. Offaly to look through it, or simply to look at it.