The Radcliffe Observatory was founded from the bequest of Dr John Radcliffe (1650-1714). Radcliffe was the leading physician of his day, and earned a large income during his lifetime. He never married, and bequeathed the majority of his estate to be used for charitable purposes at the discretion of a group of Trustees.

In 1768 the astronomer Thomas Hornsby (1733-1810) organised a successful petition to the Radcliffe Trustees for a grant for a new observatory and instruments. On 5 February 1771, he requested £1300 for an 8-foot transit instrument, two 8-foot mural quadrants, a 12-foot zenith sector and an equatorial sector, to be made by John Bird. Delivery of the instruments was delayed due to various circumstances, but by 1774 regular observations with the transit instrument and the quadrants had begun. The foundation stone for the observatory was laid on 27 June 1772, and the building was finally completed in 1793. The transit instruments and quadrants were used by Hornsby for measures of right ascensions and declinations, and he achieved a high degree of accuracy.

Hornsby was succeeded by Abraham Robertson (1751-1826) in 1810. In 1816 Robertson began what was to become a very long series of meteorological observations, which formed a considerable part of the Observatory's work. On his death, he was replaced by the mathematical historian Stephen Peter Rigaud (1774-1839), who ensured the steady continuation of the observations, but was unable to give his full attention to his work after the death of his wife in his first year as Observer.

When Rigaud died in 1839, the position of the Radcliffe Observer was changed. From its inception the post of Observer had been held jointly with the post of Savilian Professor of Astronomy with the University. After Rigaud's death the University and the Trustees could not agree on who to appoint, and the two posts were separated, with Manuel Johnson (1805-1859), a practical astronomer, becoming Observer.

Johnson was responsible for initiating the regular publication of observations. He was aided in his work by an expanded staff, which included a further three assistants and one Computer. The existing instruments were improved, and new ones were acquired, including a 7-inch Repold heliometer. This equipment was used to make systematic observations of stars within 50º of the north pole.

The next Observer was the Revd Robert Main (1808-1878), formerly Chief Assistant at the Royal Observatory, Greenwich. Main set about reorganising the equipment and had a 5-inch transit instrument installed and the heliometer overhauled. The publication of observations continued annually and the Observatory operated smoothly.

Edward James Stone (1831-1897) was appointed as Main's successor, having worked previously at the Cape Observatory. He continued the tradition of meridian work, but also concentrated on fostering a north-south link, making observations further south than any previous Oxford work. He was put in charge of arrangements for observing the 1882 transit of Venus, and drew up the final report in 1887.

Stone died suddenly, and was succeeded in 1897 by Arthur Alcock Rambaut (1895-1923). Rambaut's first task was to improve the quality of the equipment. He recommended that a large equatorial refractor be purchased to enable the Observatory to embark on photography for the first time. Its installation in 1903 brought an end to the routine meridian work of the previous 130 years and provided the first opportunity to employ photography rather than the human eye.

The new Radcliffe telescope's main programme was to cooperate in Professor Kapteyn's scheme of observing stars down to the 14th magnitude for the whole sky. In 1909 the telescope was used for the measurement of the proper motion of stars. The photographs were taken in duplicate, one being developed immediately, and the other stored for re-exposure ten years later. However, the work was not completed until after Rambaut's death in 1923.

In 1924 Harold Knox-Shaw (1885-1970) took the position of Observer and completed the proper motion work started by Rambaut. At this time, thoughts of moving the Observatory to a new site began to form and, with Knox-Shaw's desiring to take part in astrophysical programmes, a move became inevitable. By 1929 the Radcliffe Infirmary needed room for expansion and the hospital authorities began to negotiate with the Trustees for purchase of their site. Oxford's diminishing worth as an observing site and the possibility of a move to a site with clearer skies led to an agreement, and the site was sold.

Sir Frank Dyson (1868-1939), the Astronomer Royal and a member of the Radcliffe Trustees, made a visit to South Africa to examine possible new sites. A site for the new observatory was selected on a hilltop to the south-east of Pretoria. Testing of the atmospheric conditions was initiated by Dr W.H. Steavenson (1894-1975), an amateur astronomer, whose results showed the promise of a sufficiency of clear nights of high quality. The Municipality of Pretoria made a gift of 57 acres of ground to the Trustees. Legal sanction had to be obtained for the use of the capital of the Trust outside the jurisdiction of the English courts. The case was submitted to the Court of Chancery in 1934, but took another year before it was confirmed in detail. An Oxford faction lead by Professor F.A. Lindemann opposed the transfer. However, they were defeated, and in 1935 a contract was entered into with Sir Howard Grubb, Parsons and Co. Ltd of Newcastle-upon-Tyne for a 74-inch reflector, which would be the largest telescope in the Southern Hemisphere.

The new site was at Klapperkop, an old Boer fort, five miles from and 600ft above the centre of Pretoria. Grubb, Parsons ordered a 76-inch disk of glass from Corning Glass of New York State, and the third disk they cast was satisfactory. It was received in Newcastle in October 1938, but the grinding and polishing was not completed when the Second World War started in 1939. It eventually arrived in Pretoria in April 1948. The mounting and revolving steel turret had been erected in 1938, and so within a few months it was possible to begin observations.

By 1948 the Observatory buildings were complete and there was accommodation for assistants and their families. As a consequence, the site developed into a small specialized township, with the 74-inch telescope at its heart. The non-rotating parts of the telescope building were made of brick to ensure the temperature remained constant, and great care was taken to keep the temperature steady within a range of 5º fahrenheit at the level of the mirror.

After Knox-Shaw was succeeded by Dr A.D. Thackeray (1910-1978) in 1951, the 74-inch was used mainly for spectroscopy, and included Cassegrain, coudé and Newtonian spectrographs. The telescope was used for various radial velocity programmes, and in particular the study of individual stars in the Magellanic Clouds.

Until 1967 the Observatory was operated directly by the Trustees, but it also received a grant from the Department of Scientific and Industrial Research. In 1967 this changed when the Science Research Council assumed direct responsibility for the Observatory under a seven-year arrangement whereby the Trustees applied the income from the Observatory fund to the running costs. In 1972 the Observatory merged with the main South African Observatories. Thackeray and his staff, Dr M.W. Feast, P.J. Andrews and R. Catchpole, continued to work until the dismantling of the telescope, and carried out photometry of 17th magnitude stars.