Herschel, John Frederick William

English scientist, astronomer, and photographer who discovered thousands of close double stars, clusters, and nebulae. He coined the terms ‘photography’, ‘negative’, and ‘positive’, discovered sodium thiosulphite as a fixer of silver halides, and invented the cyanotype process; his inventions also include astronomical instruments.

From 1821 to 1823, with James South, he systematically remeasured the double stars discovered by his father William Herschel. He went on to revise his father's survey of the northern heavens and from 1834 to 1838 mapped the southern skies from the Cape of Good Hope Observatory in South Africa. His General Catalogue of Nebulae and Clusters, in which he coordinated into one catalogue the results of his father's, his own, and other astronomers' surveys, is still the standard reference catalogue; he had personally discovered 525 nebulae and clusters.