In 1845, William Parsons built a 72-inch reflecting telescope that dwarfed all other instruments of its day. With this “Leviathan”, Parsons discovered the spiral shape of many galaxies and studied the nature of gaseous nebula. The telescope reigned as the world’s largest for nearly 80 years and was a stunning achievement of 19th century engineering.
• Parsons was a wealthy man, and held a peerage as the 3rd Earl of Rosse in Ireland. He was trained in mathematics and had a fascination with astronomy. To build his gigantic telescope, he invented many new techniques for construction, as did William Herschel decades before.
• Built in only two years, the 72-inch telescope was mounted between two massive stones walls for support. It could only aim at objects near the meridian… the line in the sky from north to south. Still, this telescope was considered a marvelous achievement, and gained fame within the British Commonwealth.
• The mirror of the telescope was made of speculum, an alloy of copper and tin. It tarnished quickly and required re-polishing every 6 months. A second mirror was kept on hand as a replacement during polishing sessions.
A Deeper Look
• Despite frequent clouds in the blustery Irish skies, Lord Rosse was among the first to see the spiral structure of galaxies with his massive telescope.
• He was also fascinated with diffuse nebula and postulated that all nebula were simply composed of unresolved stars. Rosse strongly opposed the idea that nebula were made of gas from which stars and planets evolved. He was incorrect, of course. Not until the 20th century was it proved that nebula were made of glowing gas which eventually coalesced into stars.
• After Rosse’s death in 1867, the telescope fell into disrepair and was disassembled in 1914.
• Today at the same site in Parsontown, Ireland (now called Birr), a replica of the telescope stands as a tourist attraction at Birr Castle, Rosse’s ancestral home. But you can’t look through it for reasons of personal safety.
A sketch of the 72-inch scope at Parsonstown (now Birr, Ireland)
A Bit of History
Three years after the Leviathan of Parsonstown was disassembled in 1914, another 72-inch telescope was put into service at what’s now the Herzberg Institute for Astrophysics near Victoria, British Columbia. Unlike Rosse’s telescope, the Canadian instrument was made with modern optics, mounting technology, and a dome-shaped housing. The Plaskett telescope, as it was named, was the largest telescope in the world for a few short months until the 100-inch reflector at Mount Wilson in California saw first light. The Plaskett telescope is still used today.
Complain as I might about my own rainy clime, many of the stunning achievements of early European astronomy were based on observations from cloud-plagued countries like England, Ireland, Scotland, France, Denmark, and Germany. But the ingredients for great discovery were there: curiosity, a keen mind, a good telescope, and endless patience.