Sir John Herschel, English astronomer and scientist, 19th century.
© Science Museum / Science & Society Picture Library
Engraving by G Gabrielli. Sir John Herschel (1792-1871) discovered 525 nebulae and clusters. He 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. Published in 1875.