William Parsons, Third Earl of Rosse, 1851.
© Science Museum / Science & Society Picture Library
Engraving after a photograph by Claudet, taken from 'The Expositor: An illustrated recorder of inventions, design & art-manufacturers' by Joseph Clayton, published in 1851. William Parsons, Third Earl of Rosse (1800-1867) was a wealthy Irish aristocrat and amateur astronomer, who is best remembered for his massive telescopes. The largest, known as the 'Leviathan of Parsonstown', had a four-tonne metal mirror six feet across. This was mounted in a 15 metre wooden tube slung between huge masonry walls. It was completed in 1845 and remained the largest telescope built until 1917. Using this telescope, Rosse discovered that certain celestial objects called nebulae had spiral structures. Today, they are known to be galaxies of isolated islands of stars like our Milky Way Galaxy.