Scottish astronomer who pioneered the
use of photography to catalogue stars. He also made much use of a heliometer,
determining the solar parallax and measuring the distances of 20 of
the brighter and nearer southern stars.
Gill was born in Aberdeen and studied there at Marischal College; he
then went to Switzerland to learn clockmaking. In 1872, he became director
of Lord Lindsay's private observatory at Dun Echt, near Aberdeen. He
was astronomer at the observatory at the Cape of Good Hope, South Africa,
With Lord Lindsay, Gill went on an expedition to Mauritius 1872-78 in
order to measure the distance of the Sun and other related constants,
particularly during the 1874 transit of Venus.
In 1882 Gill realized it should be possible to chart and measure star
positions by photography. He initiated a vast project, with the help
of other observatories, to produce the Cape Durchmusterung, which gives
the positions and brightness of more than 450,000 southern stars. Gill
also served on the council for the International Astrographic Chart
and Catalogue, which was to give precise positions for all stars to
the 11th magnitude. It was not completed until 1961, although all the
photographs had been taken by 1900.