de la Rue, Warren (1815–1889)

British astronomer and instrument maker. He was a pioneer in the field of celestial photography; besides inventing the first photoheliographic telescope, he took the first photograph of a solar eclipse in 1860 and used it to prove that the prominences observed during an eclipse are of solar rather than lunar origin.

De la Rue's interest in new technologies led him to apply the art of photography to astronomy. He modified his 33-cm/13-in telescope to incorporate a wet collodion plate. His first photographs were of the Moon, and their success encouraged him to build and equip a new observatory in Cranford, Middlesex. There, de la Rue began a daily sequence of photographs of the Sun. He designed a photoheliographic telescope, virtually a long-focus camera fitted with an enlarging lens, to take to Spain for the 1860 eclipse, after which it was set up at the Kew Observatory, London. He used it to map the surface of the Sun and study the sunspot cycle. This work led to his being able to show that sunspots are in fact depressions in the Sun's atmosphere. He was elected Fellow of the Royal Society in 1850.

De la Rue was born in Guernsey, was educated in Paris, and joined his father in the printing business. He was one of the first printers to adopt electrotyping and in 1851 invented the first envelope-making machine. He also invented the silver chloride battery.