David Gill (1843-1914), British astronomer. Gill was born in Aberdeen, Scotland, but spent much of his career in South Africa. He invented the heliometer, a telescope with a divided objective that could measure the distance to the Sun. In 1879, he was appointed Her Majesty's Astronomer at the Cape of Good Hope, South Africa. While there, he made a calculation of the distance to the Sun so precise that it was used in almanacs until 1968. A pioneering astrophotographer, he also imaged the entire southern sky.