William Stephen Finsen
Template:Short description Template:Use dmy dates Template:Use South African English Template:Infobox scientist William Stephen Finsen FRAS<ref name="FRAS"/> (28 July 1905 – 16 May 1979) was a South African astronomer. He discovered a number of double stars and took many photographs of Mars. He developed the Finsen eyepiece interferometer to measure very close double stars. He was the final director of Union Observatory in South Africa from 1957 to 1965 (it was renamed Republic Observatory in 1961).<ref name="Springer"/>
Biography
Finsen was born in 1905 in Johannesburg, Transvaal Colony to Danish parents John Valgard Finsen & Marie Finsen (née Jensen).<ref name="Ancestry.com"/> He was the nephew of the Nobel Prize winner Niels Ryberg Finsen.<ref name="churchbook1852"/><ref name="churchbook1868"/> He obtained a DSc in Astronomy from the University of Cape Town and spent almost 50 years working at the Union Observatory in Johannesburg.<ref name="MNSA Obit"/> He succeeded Willem Hendrik van den Bos as director of the observatory from 1957 to 1965, during which time it changed name to the Republic Observatory (1961).<ref name="Springer"/>
Both Finsen and van den Bos were vocally opposed to South African government's plan to close and amalgamate the Republic Observatory with the Cape Observatory (Cape Town) and the Radcliffe Observatory (Pretoria) into the South African Astronomical Observatory at Sutherland, Northern Cape in 1974, as they feared it would lead to termination of the well-established programmes of observation of binary stars and asteroids. Their fears would later be proven correct as those programmes were terminated.<ref name="Docobo2012"/>
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Finsen invented an eyepiece interferometer which allowed measurement of very close double stars. His original device was used for many years at the astronomy department of the University of South Africa.<ref name="Eyepieces"/> Finsen examined more than 8 000 stars, discovered 73 double stars and took 54 000 photographs of Mars. They were considered the best photographs of Mars prior to the first space probe pictures in 1965.<ref name="ASSA 2012"/><ref name="saao2004"/> Finsen continued his observations of double stars after his official retirement from the observatory.<ref name="MNSA Obit"/>
During the second world war Finsen produced some basic films on astronomy which were used to train navigators. He also designed the Finsen Sun Compass to be used by armoured vehicle drivers in the desert campaigns. The standard magnetic compasses were useless owing to the large amount of metal in the vehicles.<ref name="MNSA Obit"/>
Finsen also developed a stomach contents sampler at the request of a specialist physician. Shaped like a pill, once swallowed the small device would open inside the patient's stomach after a pre-determined time and sample the stomach contents.<ref name="MNSA Obit"/>
Tweedledee and Tweedledum
Φ 332 (Finsen 332) is a tiny and difficult double-double star at 18:45 / +5°30', named Tweedledee and Tweedledum by Finsen, who was, by the time of his 1953 discovery, struck by the nearly identical position angles and separations of it.<ref>Sky Catalogue 2000.0, Volume 2: Double Stars, Variable Stars, and Nonstellar Objects (edited by Alan Hirshfeld and Roger W. Sinnott, 1985), Chapter 3: Glossary of Selected Astronomical Names.</ref><ref>Sky and Telescope, November 1961, page 263.</ref><ref>Deep-Sky Name Index 2000.0 - Hugh C. Maddocks (Foxon-Maddocks Associates, 1991).</ref>
Membership, awards and recognition
- The asteroid 1794 Finsen is named after him. Finsen first observed the asteroid in 1937.
- The geological feature Finsen Dorsum on the asteroid 433 Eros is named after him. Finsen had detected Eros' elongated shape.<ref name="FD"/>
- President of the ASSA 1949–1950<ref name="MNSA Obit"/>
- Awarded the Gill Medal in 1967.<ref name="MNSA Obit"/>
- Fellow of the Royal Astronomical Society – proposed in 1925 by Robert T. A. Innes<ref name="FRAS"/>