Ernst Abbe

Ernst Abbe (1840-1905) was a German physicist, mathematician and instrument maker from Eisenach whose theory of lenses shaped modern optical instruments, including those used in astronomical work. He habilitated at Jena in 1863, became extraordinary professor there in 1870 and in 1878 was appointed director of the astronomical and meteorological observatories at Jena. In partnership with Carl Zeiss he reformed lens design: he invented an apochromatic lens system for the microscope in 1868, clarified the limits to magnification and found the Abbe sine condition, which describes how a lens forms a sharp image free of coma and spherical aberration. Wealthy from his optical work, he endowed the Carl Zeiss Foundation in 1891 for scientific research and social improvement. A crater on the Moon is named for him.