John Frederick William Herschel (1792-1871), British astronomer and chemist. John, the son of the great astronomer William Herschel, continued his father's work, studying objects then called nebulae, and now called galaxies, as well as double stars. He set up an observatory in South Africa, mapping the southern skies and discovering that the Magellanic Clouds are composed of stars. Back in England, he worked on the chemistry of photography, coining the phrase 'photographic negative' and being the first to use the chemical sodium thiosulphate (hypo) as a fixing agent. He was also the first person to produce a photograph on a glass plate and to apply photography to astronomy. He was made a baronet in 1838.