On this day in 1845, a 72-inch reflecting telescope built by William Parsons, the 3rd Earl of Rosse, came into use on his estate in Ireland. The telescope remained the largest in the world until 1917, when it was eclipsed by the Hooker reflecting telescope in California.
Known as both the Leviathan of Parsonstown and Rosse six-foot telescope, it was used William Parson to observe star clusters and nebulae. For example, it was used to view a spiral nebula that we know today as the spiral galaxy Messier 51, or The Whirlpool Galaxy, which is about 31 million light years from Earth (see below). You can see The Whirlpool Galaxy today with a pair of binoculars.
Go here for more information on the Earl and his telescope.
Our Awesome Universe 