Pencil drawing on card by Sir John Herschel (1792-1871), English astronomer, mathematician and chemist, and son of Sir William Herschel. Sir John Herschel travelled to the Cape of Good Hope in 1834 with the task of establishing an observatory to catalogue the night skies of the Southern Hemisphere. The work took him five years to complete, during which time he methodically mapped the whole southern sky, cataloguing 1707 nebulae and star clusters and 2102 binary stars in the proces. Sir William Herschel had earlier catalogued the northern night sky. Sir John Herschel introduced 'hypo' (thiosulphate) as a photographic fixative and discovered the cyanotype or blueprint proces in 1842.
© National Museum of Science & Media / Science & Society Picture Library