William Parsons, 3rd Earl of Rosse (June 17,1800 - October 31, 1867) was an Irish astronomer. He improved the techniques of casting, grinding and polishing large telescope mirrors from speculum metal, and constructed steam-powered grinding machines for pa
William Parsons, 3rd Earl of Rosse (June 17,1800 - October 31, 1867) was an Irish astronomer. He improved the techniques of casting, grinding and polishing large telescope mirrors from speculum metal, and constructed steam-powered grinding machines for parabolic mirrors. His 3 foot mirror of 1839 was cast in smaller pieces, fitted together before grinding and polishing; its 1840 successor was cast in a single piece. In 1842, Parsons cast his first 6 foot mirror, but it took another five casts, before he had two ground and polished mirrors. Speculum mirrors tarnished rapidly; with two mirrors, one could be used in the telescope while the other was being re-polished. The telescope tube and supporting structure were completed in 1845. Leviathan of Parsonstown is the unofficial name of the Rosse six foot telescope. This is a historic reflecting telescope of 72 inch aperture, which was the largest telescope in the world from 1845 until the construction of the 100 inch Hooker Telescope in 1917. The Rosse six foot telescope was built by William Parsons, 3rd Earl of Rosse on his estate, Birr Castle, at Parsonstown.
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