Finsen, William Stephen

Born Johannesburg, South Africa, 28 July 1905

Died Johannesburg, South Africa, 16 May 1979

An indefatigable visual observer of southern-hemisphere double stars, William Stephan Finsen was director of the Union Observatory (later the Republic Observatory) in Johannesburg, South Africa. Born in Parktown, Johannesburg, to Danish immigrant parents, Finsen was educated at King Edward VII High School, the University of South Africa, and the University of Witwatersrand. He began his career at the Union Observatory in 1924 as a volunteer assistant under Robert Innes and worked his way up the ranks eventually to become its director, with the title Union Astronomer, in 1957. The visual measurement of double stars with the observatory’s 26.5-in. Grubb refractor comprised much of his work; he designed and built an eyepiece interferometer, which allowed him to detect pairs too close otherwise to be resolved. Finsen examined over 8,100 stars in his quest for binaries. He is credited with the...