Irish astronomer, engineer, and politician who built the largest telescope then in use. He found 15 spiral nebulae and named the Crab nebula. He was among the first to take photographs of the Moon.
Parsons was born in York and studied at Oxford. As the eldest son of a titled landowner, he was elected to Parliament while still an undergraduate to represent King's County, a seat he then held for 13 years. In 1831 he became Lord Lieutenant of County Offaly, and in 1841, on the death of his father, he entered the House of Lords. During and after the potato famine of 1846, Parsons worked to alleviate the living conditions of his tenants.
Determined to construct a large telescope, Parsons learned to cast and grind mirrors. Fourteen years after his experiments began, he was able to make a 92-cm/36-in solid mirror, and in 1842 he cast the 'Leviathan of Parsonstown', a disc 1.8 m/72 in in diameter which weighed nearly 4 tonnes and was incorporated into a telescope with a focal length of 16.2 m/54 ft. It took three years to put together. He also invented a clockwork drive for the large equatorial mounting of an observatory.