British astronomer and instrumentmaker who pioneereed celestial photography. Besides inventing the first photoheliographic telescope, he took the first photograph of a solar eclipse 1860 and used it to prove that the prominences observed during an eclipse are of solar rather than lunar origin.
De la Rue was born in Guernsey and joined his father in the printing business. He was one of the first printers to adopt electrotyping and in 1851 he invented the first envelope-making machine. He also invented the silver chloride battery.
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 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.