Sir John HerschelDied 11 May 1871 at age 79 (born 7 Mar 1792). Sir John Frederick William Herschel was an English astronomer, chemist and chemist (1st Baronet), who, as asuccessor to his father Sir William Herschel, discovered a further 525 nebulae and clusters. John Herschel was a pioneer in celestial photography, and as a chemist contributed to the development of sensitized photographic paper (independently of Henry Talbot). In 1819, he discovered that sodium thiosulphate dissolved silver salts, as used in developing photographs. He introduced the terms positive image and negative image. Being diverse in his research, he also studied physical and geometrical optics, birefringence of crystals, spectrum analysis, and the interference of light and sound waves. To compare the brightness of stars, he invented the astrometer. |
