Sir David Gill (1843-1914), British astronomer. Although trained in the family business of watchmaking, Gill sold his father's shop to pursue astronomy. He invented the heliometer, a telescope with divided objective that could measure the distance to the Sun. Soon after, in 1879, he was appointed Her Majesty's Astronomer at the Cape of Good Hope, South Africa. He modernised the observatory, and with new, accurate instruments 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. He won the Bruce and Gold Medals of the Royal Astronomical Society, and served as president of the society from 1909-11.