Leviathan of Parsonstown

The Leviathan of Parsonstown was the telescope that Lord Rosse, also known as William Parsons, 3rd Earl of Rosse (mentioned in the two previous posts), built in Parsonstown, Ireland, now known as Birr and situated at what is known as Birr Castle. That telescope was the telescope that trumped all telescopes of that century. It was a big mother of a telescope. It was 72 inches in diameter.

The telescope’s mirror was made of speculum metal. What is speculum metal, you ask? Speculum metal is a very hard white alloy consisting of a 4:1 ratio of copper to tin. To be more exact, percentage-wise, it is 67% copper and 33% tin. The problem with speculum metal is that it is prone to tarnishing. Because of Ireland’s damp weather, the mirror had to be repolished every six months. They even built an extra mirror to be put in place while the other was receiving its bi-annual polish treatment.

The telescope was powerful and exceeded the expectations of the time-period, enabling astronomers to observe 18th magnitude stars and spiral galaxies. But, even with this gigantic, powerful telescope, Ireland’s sky was certainly not the best for observing. Wikipedia notes that there were only about 60 clear nights of viewing per year.

You can read more about Lord Rosse and his gargantuan telescope here: http://www.birrcastle.com/