William Parsons, 3rd Earl of Rosse KP PRS ( June 17, 1800 - October 31, 1867 ) was an Anglo-Irish astronomer who had several telescopes built. His 72-inch telescope, built in 1845 and colloquially known as the "Leviathan of Parsonstown," was the world's largest telescope, in terms of aperture size, until the early 20th century. From 1807 until 1841, he was styled as Baron Oxmantown.
Sir Robert Stawell Ball FRS (July 1, 1840 - November 25, 1913) was an Irish astronomer who founded the screw theory. He was the son of naturalist Robert Ball and Amelia Gresley Hellicar. He was born in Dublin. Ball worked for Lord Rosse from 1865 to 1867. In 1867 he became Professor of Applied Mathematics at the Royal College of Science in Dublin. There he lectured on mechanics and published an elementary account of the science. In 1874 Ball was appointed Royal Astronomer of Ireland and Andrews Professor of Astronomy in the University of Dublin at Dunsink Observatory. In 1908 he published A Treatise on Spherical Astronomy, which is a textbook on astronomy starting from spherical trigonometry and the celestial sphere, considering atmospheric refraction and aberration of light, and introducing basic use of a generalised instrument.