John Herschel's drawing of a spectrum, c 1830s.
© Science Museum / Science & Society Picture Library
Pictured is John Herschel's drawing of a spectrum and an indication of the action of the sun's atmosphere, experiment 1084 from his own notebook. Herschel (1792-1871) was an English astronomer, mathematician and chemist who discovered 525 nebulae and clusters. He pioneered celestial photography and invented the cyanotype or blueprint proces.