The man who named Saturn's moons also invented the blueprint
John Herschel gave seven of Saturn's moons the names astronomers still use, from Mimas to Iapetus. He also invented the cyanotype, the process behind blueprints, made a photograph on glass in 1839, and wrote a book on scientific method that fired a young Charles Darwin, whom he later hosted in Cape Town.
Born in Slough in 1792, John was the son of William Herschel, discoverer of Uranus, and nephew of the astronomer Caroline Herschel. At Cambridge he graduated as Senior Wrangler in 1813 and befriended Charles Babbage and George Peacock. From 1816 he worked with his father, building a reflecting telescope with an 18-inch mirror, and he went on to name four moons of Uranus as well. He brought the Julian day count into astronomy and discovered galaxies including NGC 7.
His Preliminary Discourse of 1831 argued that nature runs on laws that are hard to see, and that inductive reasoning toward a single unifying explanation is science's highest aim. It became hugely influential at Cambridge, where the student Darwin felt a burning enthusiasm after reading it. Herschel also correctly blamed astigmatism on an irregular cornea and imagined correcting vision with jelly held against the eye in a glass capsule, an early sketch of the contact lens idea.
In November 1833 he paid £500 of his own money to sail from Portsmouth to the Cape with his wife, three children and a 20-inch telescope, aiming to extend his father's survey to the southern sky. From an estate called Feldhausen below Table Mountain he watched Halley's Comet return. With his wife Margaret he produced 131 fine drawings of Cape plants, and he received Darwin and Captain FitzRoy of HMS Beagle on 3 June 1836. He later called those years probably the happiest of his life.
Back in England in 1838 he was made a baronet, and in 1847 his results from the Cape won him a second Copley Medal. His photographic work ranged from the cyanotype and its cousin the chrysotype to early colour experiments, and he studied colour blindness and the chemical effects of ultraviolet light. In 1864 he issued the General Catalogue of Nebulae and Clusters, merging his work with his father's. He died in 1871, and a village in South Africa's Eastern Cape bears his name.
Source: John Herschel
