Sir David Gill
Ascension Island, 1977

Sir David Gill (1843–1914) was a Scottish astronomer who devoted much effort to establishing the distance between the Earth and the Sun, the so-called astronomical unit. One way of doing this is to measure the distance between the Earth and another planet. In 1877 Gill visited Ascension Island in the Atlantic Ocean in an attempt to measure the parallax of Mars during one of its periodic close approaches to us; the place where he set up his observatory is still called Mars Bay. His wife published an account of the trip titled Six Months in Ascension.

This set of four stamps from Ascension Island commemorates the centenary of Gill’s visit. The first three, rather sketchily drawn, are captioned: “Mars Bay location 1877” (3p); “Mars Bay & instrument sites” (8p); “Sir David & Lady Gill at the site of their living tent” (12p). The 25p stamp shows a map of the southwest part of the island with Gill’s observatory site labelled in red.

Stanley Gibbons nos. 229–232