Leviathan of Parsonstown

In 1845, William Parsons, an Irish nobleman and the third Earl of Rosse, constructed a large telescope with an enormous 6-feet wide mirror on his estate Birr Castle, at Parsonstown in what is present day Birr, in Ireland. The telescope was so large that locals began to call it the “Leviathan of Parsonstown” — the leviathan is a sea monster or a whale in modern Hebrew. It was the largest telescope in the world at that time, a title it proudly held until the construction of the 100-inch Hooker telescope at the Mount Wilson Observatory, California, in 1917. William Parsons built several telescopes in his lifetime, and the Leviathan of Parsonstown was the pinnacle of his achievements. With his great telescope, Parsons studied nebulas and discovered that these blurry objects are not not truly gaseous but contained fine stars that previous telescopes couldn't resolve individually. The Leviathan was the first to reveal the spiral structure of M51, a galaxy nicknamed later as the "Whirlpool Galaxy", and his drawings of it closely resemble modern photographs. Photo credit: National Library of Ireland/Wikimedia To the build the Leviathan of Parsonstown, which had no precedent, William Parsons had to invent many techniques of telescope construction and perfect techniques of casting, grinding and polishing large telescope mirrors from speculum, an alloy of copper and tin. While earlier telescope builders guarded their secrets, William Parsons made his widely available. He published details of his techniques and presented them to the Belfast Natural History Society. The images he obtained using his telescope were widely circulated within the British commonwealth. Parsons took five tries before he created a mirror that could be used, and 3 years to build the actual telescope. The mirror was 5 inches thick and weighed almost 3 tons. The telescope was mounted between two massive stone walls for support.