Observers of celestial objects owe a lot to this English dude.
This picture of Lord Rosse’s 72-inch telescope was taken in 2022.
Credit: DixonD/WikiMedia Commons
William Parsons, 3rd Earl of Rosse, was born on the date I’m posting this article (June 17) way back in 1800, in York, England. Astronomers know him as the person who built (OK, he supervised the construction) and used the largest telescope in the 19th century. It wasn’t surpblocked in aperture until the construction of the 100-inch Hooker Telescope at Mount Wilson Observatory in 1917.
Largest eye on the sky
Dubbed the “Leviathan of Parsonstown,” its main mirror (made of speculum — a mixture of two-thirds copper and one-third tin) measured 72 inches across. He installed it at Birr Castle, which was in Parsonstown. In fact, Parsons ground two mirrors so that one could be used in the telescope while the other was being re-polished. Speculum tarnishes rapidly, so there was a continual need to do this.
The telescope was a mechanical marvel into which Lord Rosse incorporated a lot of creative thinking. He started building it in 1842 and finished it three years later. Upon completion, it replaced the 36-inch reflector he had been using. The Leviathan was balanced so well that, despite it weighing 16 tons, two men could easily point it to any spot in the sky.
Credit: WikiMedia Commons
Worthy observations
Lord Rosse used the Leviathan to study nebulae. Today, that word means “a cloud of cosmic gas that’s either emitting, reflecting, or absorbing light.” But in Parsons’ time, it meant “any unresolvable object visible through a telescope.” This included galaxies.
One of Lord Rosse’s greatest discoveries was the spiral structure of the Whirlpool Galaxy (M51). He also made a sketch of a nebula in the constellation Taurus the Bull. Because of the shape he drew, we still refer to it as the Crab Nebula (M1).
The Leviathan of Parsonstown remained in use until 1890. The restoration of this giant instrument was completed in 1997.
