Royal Observatory Cape of Good Hope

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Royal Observatory, Cape of Good Hope
Ensign of the Royal Navy animated.gif
Astronomical Observatory overview
JurisdictionGovernment of the United Kingdom
HeadquartersObservatory, Cape Town
Astronomical Observatory executive
  • HM Astronomer, Cape of Good Hope
Parent Astronomical ObservatoryDepartment of Admiralty

The Royal Observatory, Cape of Good Hope, is the oldest continuously existing scientific institution in South Africa. Founded by the British Board of Longitude in 1820, it now forms the headquarters building of the South African Astronomical Observatory.


The proposal for a Southern observatory in all likelihood originated among the same group of people who founded the Royal Astronomical Society in the United Kingdom.[1] Its official establishment took place on 20 October 1820 through an Order in Council of King George IV of the United Kingdom. It remained a separate entity until 1972 when it was amalgamated with the Republic Observatory Johannesburg to form the present-day South African Astronomical Observatory. Its site is now the headquarters of the South African Astronomical Observatory.

The Royal Observatory was responsible for a number of significant events in the history of astronomy. The second HM Astronomer, Thomas Henderson, aided by his assistant, Lieutenant William Meadows, made the first observations that led to a believable stellar parallax, namely of Alpha Centauri. However, he lost priority as the discoverer of stellar parallax to Friedrich Wilhelm Bessel who published his own (later) observations of 61 Cygni before Henderson got around to his.[2][3] Around 1840, Thomas Maclear re-measured the controversial meridian of Nicolas-Louis de La Caille, showing that the latter's geodetic measurements had been correct but that nearby mountains had affected his latitude determinations[4][5]

In 1882 David Gill obtained long-exposure photographs of the great comet of that year showing the presence of stars in the background. This led him to undertake in collaboration with J.C. Kapteyn of Groningen the Cape Photographic Durchmusterung, the first stellar catalogue prepared by photographic means. In 1886, he proposed to Admiral A.E.B. Mouchez of Paris Observatory the holding of an international congress to promote a photographic catalogue of the whole sky. In 1887 this congress took place in Paris and resulted in the Carte du Ciel project. The Cape Observatory was assigned the zone between declinations −40° and −52°. The Carte du Ciel is regarded as the precursor of the International Astronomical Union.

In accordance with its mandate, the principal activity of the Observatory was Astrometry and it was over its existence responsible for publishing many catalogues of star positions. In the 20th century it turned in part towards Astrophysics but by the nineteen-fifties the city lights of Cape Town had rendered work on faint objects impossible and a new site in the Karoo semi-desert was sought. An agreement to facilitate this was ratified on 23 September 1970.Nevertheless, several telescopes remained in operation until the 1990s. These are rarely made use of today except for public outreach events. Alan Cousins was the last serious observer to work from the Royal Observatory site.

In Command

HM Astronomer, Cape of Good Hope

  1. Fearon Fallows (1820-1831)
  2. Thomas Henderson (1831-1833)
  3. Thomas Maclear (1833-1870)
  4. Edward James Stone (1870-1879)
  5. David Gill (1879-1907)
  6. Sydney Samuel Hough (1907-1923)
  7. Harold Spencer Jones (1923-1933)
  8. John Jackson 1(933–1950)
  9. Richard Hugh Stoy (1950–1968)
  10. George Alfred Harding was Officer-in-charge (1969–1971)


  1. Warner, Brian (1979). Astronomers at the Royal Observatory Cape of Good Hope. A.A. Balkema.
  2. Henderson, T. (1840). "On the Parallax of α Centauri". Memoirs of the Royal Astronomical Society. XI: 61–68.
  3. Glass, I.S. (2008). Proxima: The Nearest Star (other than the Sun). Cape Town: Mons Mensa.
  4. Maclear, Sir Thomas (1866). Verification and Extension of La Caille's Arc of Meridian at the Cape of Good Hope. Lords Commissioners of the Admiralty.
  5. Glass, I.S. (2012). Nicolas-Louis de La Caille, Astronomer and Geodesist. Oxford University Press.