Sir John Herschel, English astronomer, c 1860s.
© Science Museum / Science & Society Picture Library
Photographic portrait of Herschel (1792-1871). Son of famous astronomer Sir William Herschel (1738-1822), John Herschel continued his father's work by mapping the Southern Skies which he observed from Feldhausen House near Table Mountain at Claremont, Cape Town, South Africa. Using a 20-foot reflecting telescope, he discovered thousands of new celestial objects whose position he carefully plotted. These were later published as 'Results of Astronomical Observations made 1834-8 at the Cape of Good Hope' (1847). Herschel discovered 525 nebulae and clusters; pioneered celestial photography, discovering the cyanotype or blueprint proces in 1842; and carried out research on photo-active chemicals and the wave theory of light.