[1][2] The observatory and its former annex, the § Leiden Southern Station, are known for the discovery of 6,000 double stars and for Proxima Centauri, made by astronomer Robert Innes.

[4]: 18  The land was given only for the use of science and a road, later called Observatory Avenue, was also to be built close to the site.

[4]: 18  The observatory building was built and the formal opening took place on 17 January 1905 by Governor Milner, but had no astronomical equipment.

[4]: 19 In 1906 it was lent a Hamberg universal instrument (2 5/8-inch object glass) by Dr Oskar Backlund.

Well remembered for the quality of its Directors, work done on minor planets and the discovery of Proxima Centauri, growing light pollution problems in Johannesburg led to its closure in 1971–1972.

The main Cape telescopes were moved to Sutherland, and the Radcliffe Observatory at Pretoria was also dismantled.