Republic Observatory

Also known as Johannesburg or Union Observatory
1903 – 1971

Note: The name of the Observatory changed three times, reflecting  the political changes in South Africa during its existence. The official names were as follows: [Personal communication with Vermeulen; cdc]

Transvaal Meteorological Department 1903 – 1909
Transvaal Observatory 1909 – 1912
Union Observatory 1912 – 1961
Republic Observatory 1961 – 1971


Current Information:
  • The  Observatory closed down. The Current Information section is not relevant to this Observatory.
  • In the late 1960s, an amalgamation of astronomical facilities in  South Africa took place in order to form the current S.A.A.O. Some of the instruments were moved to Sutherland in the  Karoo.


  • The  buildings still exist. Address: 18a Gill Street, Observatory, Johannesburg

In Brief:

Noted  for:

  • Between  1911 and 1938 the Observatory detected 579 new minor planets.  At the time it was a record for any institution.
  • Discovery of Proxima Centauri, faint companion star of Alpha Centauri,  made by Innes.
  • Discovery of over 6 000 double stars and cataloguing over 20 000 double stars. [Personal communication with Vermeulen]


  • The Observatory was initially known as the Transvaal Meteorological  Department, and as the name indicate, the main concern was  the weather. Due to political and administrative changes and the  vigour of R.T.A. Innes  (1st Director) and subsequent Directors, the observatory became an excellent astronomical institution. However, growing light pollution problems in Johannesburg and the next set of political / administrative changes led to the closure of this excellent  facility. The observatory is well remembered for the quality of its Directors, work done on minor planets and the discovery of Proxima Centauri. Unfortunately it is also an excellent example  of the great affect the temporal political world (real world) can have on astronomy.
    [Errata: Moore refers to the Observatory as the ‘Government Meteorological Observatory’. This is incorrect, as it initially used to be called the ‘Transvaal Meteorological Department’.] [Personal communication  with Vermeulen]
  • Due to very close ties with Leiden Observatory in Holland, an agreement of co-operation was reached in 1923 between the Union and Leiden Observatories. Astronomers from each establishment  were free to make use of the facilities of the other. Since the  night skies in Transvaal were infinitely better than in Holland,  the flow of visiting astronomers was virtually one way. By 1929 Leiden Observatory decided to send a telescope and permanent staff to Union Observatory. In 1938 the Rockefeller  twin telescope was installed. With the growing light pollution problem in Johannesburg it was decided to establish an outstation  at Hartebeespoort. This became known as the Leiden Southern Station.  The facility was administered by the Union (later Republic) Observatory.  Some of the Union observatory instruments were also moved to the  site. After the Republic Observatory closed down, the Leiden Southern  station continued to operate until it was sold to Pretoria Technikon.  For more, look Leiden Southern Station.
  • Light pollution is an International problem, and in the 1960’s three of South Africa’s Observatories were badly affected by light pollution. They were the Cape Observatory (Cape Town), Radcliffe Observatory (Pretoria) and Republic Observatory (Johannesburg). By an agreement between the South African CSIR and the British Science Research Council (23 September 1970), a new facility was created away from light pollution at Sutherland in the Karoo. The main instruments from the Cape and Johannesburg Observatories were moved to the new sight, and the Cape Observatory grounds became the headquarters for the new South African Observatories (today the South African Astronomical Observatory S.A.A.O.)
    Radcliffe Observatory closed down, and its 74-inch telescope was bought and moved to Sutherland.
    The Johannesburg Observatory thus meta-morphed into a new entity, the
    S.A.A.O., which for reasons of convenience and space will be dealt with in this website as a separate establishment.

Historical background:

Historical Index: Transvaal Meteorological; Transvaal; Union; Republic; Amalgamation

Transvaal Meteorological Department:
There was no Observatory in the Transvaal (previously a Republic and later a province in South Africa) and the climate was superb.  On 29 October 1902, the South African Association for the Advancement  of Science petitioned the Government to establish an observatory  in or near Johannesburg, “for the collection and distribution of meteorological observations throughout the Transvaal Colony”. Although astronomy was mentioned it was deemed that meteorological aspects were more important. [Hers; Smits]
On  17 December 1902 the Assistant Colonial Secretary, W H Moor advised that the project had been approved. He invited David Gill from the Royal Observatory, Cape of Good Hope, to assist with “securing the best man available as Director of the department”. Gill suggested R TA Innes as Director, a most interesting and capable person. [Hers] (Look Astronomers: Innes)
The Transvaal Meteorological Department started operating on 1 April 1903, but only officially came into existence on 17 January 1905. Lord Milner performed the opening ceremony.
Sir Herbert Baker, well-known South African architect,  designed the Observatory buildings. A house was also designed for the Director, although this building was not built until 1910. [Hers]

Transvaal Observatory:
 The name was changed in 1909 to the Transvaal Observatory.  [Personal communication with Vermeulen]
Meteorology was the first concern, and in the beginning, astronomy played  only a minor role, until S.A. became a Union (1910). When the four states (Transvaal, Orange Free State, Cape and Natal) merged  into the Union of South Africa, their meteorological services were combined into the Union Meteorological Department. Only then  could the Transvaal Observatory devote its time to astronomy. (South Africa became a Union in 1910, but the name change to Union  Observatory only took place on 1 April 1912.) In 1907 the observatory  required its first telescope, and with Innes as a pro-astronomy Director, the transition started towards astronomy.
The  Observatory started with the unusual step of receiving its first  telescope on permanent loan basis from the Royal Observatory, Cape of Good Hope. [Laing, p.4] (“The first astronomical instrument erected on site was a 2 5/8-inch refractor, loaned to them by Dr.  Oskar Buckland, for use with the International Latitude Program”  [Smits, p.16.] More info needed)
Installation of a 9 inch telescope in 1907. In 1924 this telescope was  renamed the Reunert Telescope. [Smits]

Union Observatory:
 The Observatory achieved its greatest fame during the time that it was known as the Union Observatory (1912-1961). The Directors  were known as Union Astronomers, there were four:
Innes (1903-) 1912-1927
Wood 1927-1941
Van den Bos 1941-1956
Finsen 1957-1961 (-1965)
The National Time Service for South Africa was stationed at the Union Observatory. Jan Hers was put in charge of this department.  The old Meteorological Observatory was changed into a building  housing the clocks, as well as a seismometer. Later on the time  service was taken over by the CSIR, and after the Observatory closed, it moved to other premises. [Smits]
1923: Agreement between Leiden and Union Observatories whereby the facilities of the two institutions were made available  to each other. Since the night sky in the Transvaal is much better  than in Holland, most of the observers went from Holland to South Africa. (This eventually led to the establishment of the Leiden Southern Station.) [Moore, p.107; Smits, p.20.]
1938: As part of the agreement between Union and Leiden Observatories,  the Union Government provided funds for building new facilities on the terrain. This was to house the Rockefeller  twin 16-inch telescope, which belonged to Leiden, but administered  by Union Observatory.
Due  to growing light pollution problems in Johannesburg, Leiden decided  to move to a new sight at Hartebeespoort. (Look Leiden Southern Station.) The agreement was that Leiden Observers  operated Hartebeespoort, but it was an official outstation of the Union Observatory. As such it came under Finsen’s jurisdiction even though it was virtually autonomous. (director was
Walraven)  The Rockefeller twin and 10 inch Franklin – Adams telescopes were moved to Hartebeespoort, even though the latter was the property of the Union Observatory.

Republic Observatory:
 In 1961, when South Africa became a Republic, the name was  changed to the Republic Observatory.
In 1964 it became part of the Council for Scientific and Industrial Research (C.S.I.R.)
During  1962 – 64 a new office block with a library was erected, with two domes on its roof. The Reunert– and Franklin Adam twin telescopes were moved here. [Hers]
It was planned to erect a 74-inch telescope, and to this end a mirror blank was ordered. This telescope never materialised. [Moore,  p.104; Smits] (This proposed 74 inch telescoped must not be confused  with the Radcliffe 74 inch telescope)
The Lowell Observatory International Planetary Patrol started in 1969. It ran for five years and was virtually the death blow to the Observatory double star  observing. van den Bos and De Klerk tried for a short while to  share the Innes refractor with the patrols program, but this was  not successful and all double star observation came to a halt.  [Personal Communication with G. Roberts who worked at the Observatory.]

The  South African Government decided to amalgamate all astronomical research into one body, which later became known as the South African Astronomical Observatory (S.A.A.O.). This meant that the Republic Observatory had to close down. “The first official  rumblings came on 23 September 1970, when the CSIR authorities announced that there had been agreement with the British Science  Research Council for the setting-up of the combined South African Observatories; the Cape would be the headquarters and Sutherland the outstation, 235 miles away across the Karoo, with Sir Richard  Woolley as Director. This meant – as we have already noted  – that the main Cape telescopes would be moved to Sutherland, while the Radcliffe Observatory at Pretoria would be dismantled altogether. But what about Johannesburg?” [Copied from Moore,  p. 104.]
This decision met with great opposition. “In an article in Nature, dated 29 January 1971, van den Bos wrote as follows:  “The 26.5 inch refractor, with which the Observatory built up its reputation in double star observation, is little, if at all, affected by sky illumination or smog and the time-tested ‘seeing’ remains as good as ever. There is no reason why it should not be usefully employed at this work, at its present site, for  many years to come . . . Even if the observatory were moved en  bloc to Sutherland it would remain more than doubtful whether  its largely astrometric programmes could be continued there as  successfully as in Johannesburg or Hartebeespoort . . . The minor planet work would be seriously affected by transfer from the clear winter skies of the High Veld, of that there is no doubt, for  it is in winter, when the ecliptic is south of the equator, that  the programme reaches its peak. Furthermore, double-star work  in particular is of an intensive, long-term and personal nature.”
Finsen was in full agreement that to close the Republic Observatory  would be a tragic miscalculation – and he was not alone in his  views. Yet in many ways the situation was curious; after Finsen’s  official retirement as Director in 1965, no successor had been  appointed and although the programmes were being continued much  of the impetus had gone.
Other arguments also were advanced. Killing the Republic Observatory would leave South Africa’s largest city without any major astronomical institute and presumably the Library, second only to that at the Cape, would also go. Shifting the 26.5-inch itself would have been impracticable even if it had fitted into the proposed programme for Sutherland – which it did not. The situation was still fluid  when the International Astronomical Union, the controlling body of world astronomy, met in 1972 (it meets every three years; the 1972 venue was at Brighton, in England). Misgivings were expressed by the Commission’s dealing with minor planets and with double  stars. In the official report published after the congress there  was a comment from Dr P. Herget, the famous American asteroid  observer, to Dr F.J. Hewitt, Vice-President of the CSIR in Pretoria:  “There have been more observations of more minor planets  made at the Johannesburg Observatory (and the annexe at Hartebeespoort) than at any other observatory in the Southern Hemisphere in the whole history of astronomy. To destroy this treasure-trove of  observations will surely bring you lasting and increasing condemnation  as the years go on.” And from the Double Star Commission, it’s President, Dr J. Dommanget, wrote, “unfortunately, as a consequence of recent re-organizations of the astronomical research  in South Africa, practically all research work in the double star  field in the Southern Hemisphere has been interrupted. It is imperative that immediate interest is paid by some astronomers in double star research, and effective support given to continuous observations”.
It is probably true to say that the proposed demise of the Republic  Observatory caused arguments which were more heated than any in the whole story of South African astronomy”. [Copied from  Moore p. 105.]
In 1972 some of the instruments were moved to Sutherland.


List of Directors:

  • Innes R.T.A. He was the first Director (1905-1927) (Started working  in 1903, but the Observatory was not official until 1905 / 1905 – 1912 Government Meteorological Observatory / 1905 – 1912 Union Observatory.) He was a remarkable person with a special interest in double stars, which set the trend for the observatory to become one of the best double star research institutions in  the world. With the name change to Union Observatory “it  is said that he [Innes] is the only man who has been transformed from a meteorologist into an astronomer by an act of Parliament”.  [Moore, pp. 98-99.]
  • Wood (1927-1941 Union Observatory) became Director upon Innes’s retirement. He was an avid comet, asteroid and minor planet hunter. Woods time, as Director, was a period of consolidation.
  • Van den Bos (1941-1956 Union Observatory) During his Directorship,  quarts clocks were installed and Johannesburg became the “Greenwich” of South Africa.
  • Finsen (1957-1961 Union Observatory / 1961- 1965 Republic Observatory) It was during his Directorship that the Republic Observatory became part of the CSIR.
  • Hers J. (1965-1971 Republic Observatory) During his Directorship  the CSIR decided to close down and amalgamate the Observatories.


  • C. Jackson (Union Observatory 1928 – 1947) Asteroid Hunter. He  became Director at Yale – Columbia Southern Station, Johannesburg (1947 – 1951), and Director at Yale – Columbia Southern Station, El Leoncito, Argentina. (1963 – 1966)
  • E.L. Johnson: asteroid hunters
  • J.A. Bruwer: asteroid hunters
  • H. van Gent: asteroid hunters





Pictorial Sources:


  • Hers, J., The History of the Transvaal Observatory. 1, 2 & 3, MNASSA,  Vol. 46, Nos. 1 & 2 [Feb], 3 & 4 [April], 5 & 6 [June],  1987 (As well as personal communications between Hers and Smits)
  • Laing, J.D. (ed.), The Royal Observatory at the Cape of Good Hope 1820  – 1970 Sesquicentennial Offerings, p. 4.
  • Moore, P. & Collins, P., Astronomy in Southern Africa, pp. 92 – 106.  (General Source)
  • Smits, P., A Brief History of Astronomy in Southern Africa. (Unpublished)
  • The  South African Astronomical Observatory, pp. 16 – 18.
    (Publication of SAAO, no author, no date)


The Year Reports of the Johannesburg Observatory is available in a digital format.

– In 1968 the Royal Observatory in Cape Town ceased it’s formal  existence and became part of a joint venture between the South African  CSIR and the Science Research Council, known as the South African Astronomical Observatory. At the same time, the Republic (formerly Union) Observatory in Johannesburg was closed down. The library  and some of the archival material from the latter were sent to the  SAAO, but most early papers were transferred to the Archives attached to the CSIR Library in Pretoria.
-The bulk of the material is concerned with the establishment and  instruments of the Union Observatory. Gill’s and Innes’s correspondence on these subjects include a letter to Boss on the selection of the site, extensive exchanges with Turner and Grubb, and negotiations  with the firms of Grubb, Cooke, Repsold, Hilger and Chance, 1903-26.  There are notes by Innes on the construction of the 26-inch refractor.
-The siting and use of the Franklin Adams telescope is covered by  correspondence between Innes and Franklin Adams, H. E. Wood, T. Cooke and various officials.
-Most of the correspondence between the Union Observatory and other  observatories is preserved. Correspondence with individuals has  been filed by country and by individual and include inter alia Spencer  Jones, Dyson, Comrie, Lockyer, Turner, Eddington, Crommelin, Phillips  in England; G. Struve, Hertzsprung, Kapteyn, de Sitter, Pannekoek,  E. Stromgren and many others in Europe; Boss, Schlesinger, Brown,  Hill, Shapley, Burnham and very many others in the USA.


Many thanks to Dirk Vermeulen who helped with the page on the Republic  Observatory.


In Southern Africa there were two great depositories of astronomical books. The one is the library of the Royal Observatory, Cape of Good Hope, now the S.A.A.O. This library and it’s contents still exists with no obvious threat to it. The other great depository was the Republic Observatory. When the Observatory closed down various institutions were contacted to find out if anyone would be interested in taking over the books. All the institutions declined mainly due to financial  constraints. Some of the books went to Sutherland. It is unknown  what happened to the rest. Any information will be welcome. [Personal communication with Jan Hers. 17/05/2003 cdc]


Interesting Links:


 RepObs-02rThe opening of the Goverment Meteorological Department by Lord Milner.
Source: MNASSA.

The Goverment Meteorological Department in 1905, better known as Union Observatory. Later renamed to Republic Observatory.
Courtesy Africana Museum. Source: Moore

RepObs-04r26-inch Telescope Dome and Library at the Republic Observatory.
Source: A.S.S.A. Archives: Peter Smits Collection.

RepObs-05rRepublic Observatory.
Source: A.S.S.A. Archives: Peter Smits Collection.