Sir John Herschel, English astronomer, c 1860s.
© Science Museum / Science & Society Picture Library
Photoglyphic engraving from daguerreotype by Mayall. 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. John Mayall (1810-1901) was one of the most commercially succesful photographers in London; he contributed to the popularity of carte-de-visites after producing some of Queen Victoria and the Royal family in the 1860s.