1843-1914

Scottish astronomer and pioneer in applying photography to astronomy. As director of South Africa's Cape Observatory (1879-1907), he conducted a photographic survey of the southern skies. Gill and J. C. Kapteyn measured the plates (1886-98) and published the positions and magnitudes of over 400,000 stars. Their survey was the basis for later work on stellar distribution. In 1888 Gill redetermined the distance between the Sun and Earth to within one part in a thousand.