The Yapp Dome

The Yapp Dome in 1935. © BT Heritage. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial-ShareAlike (CC BY-NC-SA) licence (see below)

On 13 March 1931, William Johnstone Yapp offered to present the Observatory with a large telescope as an appreciation of the personal work of the Astronomer Royal, Frank Dyson. After careful consideration it was decided to order a 36-inch reflector with a spectroscope and a new 34-foot dome at a cost of £15,000. An order for the telescope and dome was placed with Messrs. Sir Howard Grubb, Parsons & Co soon after. The telescope became known as the Yapp 36-inch Reflector.

As there was no space on the main site, the telescope was set up on the west side of the Christie Enclosure, a few hundred metres to the east across the Park. The building was designed by the Admiralty’s Civil Engineer-in-Chief, in accordance with the requirements of the Astronomer Royal and of the contractors for the instruments. The building and dome were completed in late 1932. The telescope was installed later with the help of a block and tackle. Described by Charles Davidson in 1934 as being constructed from ‘a pleasing red brick’, the building had two floors. The observing room was at first floor level and entered directly from the east side via an external flight of steps. Below it at ground floor level there was a store and lavatory. The building also contained a silvering room in a small wing located on the north side of the building at right angles to the entrance. The dome was clad in copper and rotated by means of an endless cable driven by an electric motor. The cost of the building was estimated at £4,600, of which £2,180 was for the dome.

Sectional view though the dome and piers. From 36 in. Reflecting Telescope of the Royal Observatory, Greenwich (Reprinted from The Engineer, 18 & 25 May, 1934). Sir Howard Grubb, Parsons and Company, Publication No.11 (1934).

The Yapp Telescope in 1935 with the slitless spectroscope attached. © BT Heritage. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial-ShareAlike (CC BY-NC-SA) licence (see below)

In April 1946, it was announced that the Observatory would be moving to Herstmonceux. Of all the domes at Greenwich, that of the Yapp was the only one that it was felt would definitely be required there – a position that was affirmed in writing in October 1947. Meanwhile, following a visit to Greenwich in June 1947, the Ministry of works considered that the Yapp Dome might be suitable for housing a planetarium. Any prospects of this happening were dashed in 1949 after the Science Museum’s deputy director Mr Davis indicated that it was too small ‘for a modern planetarium’ and that a dome of at least 70-foot diameter was required. At about the same time the Treasury and Ministry of Education met to discuss the possible installation of a planetarium in the new centre block of the Science Museum. These plans came to nothing. Meanwhile, the development of the equatorial group at Herstmonceux had run into difficulties following the intervention of the Royal Fine Art Commission and new plans were evolved to erect a set of buildings with matching domes.

In 1951, the Yapp Dome at Greenwich was under consideration for possible use as a park shelter. With the move of the telescope to Herstmonceux imminent, the future prospects for the building began to change. Spencer Jones wrote to the Admiralty on 26 July 1955 suggesting that the Dome be sold to Messrs. Cox, Hargreaves and Thompson Ltd who had requested it for re-erection at Kivu in the Belgian Congo on behalf of the Belgian Institut pour la Recherche Scientifique en Afrique Centrale. At this point, although the Admiralty had no objections, there was uncertainty as to whether it was they or the Ministry of Works (to whom the building was to revert on behalf of the Crown) had the authority to give the go ahead. In view of the delay and uncertainty that might be involved, the request to purchase the dome was withdrawn and it looked as though the dome might be scrapped. This however didn’t happen. By August 1956, discussions were underway to have it transferred to the Royal Observatory, Cape of Good Hope in South Africa, which like the Observatory in Greenwich was under the control of the Admiralty. There it was planned to use it for the Elizabeth telescope – a one-metre reflector conceived in 1953 in the Queen’s coronation year and finally opened in 1964. Building work at the Cape started in April 1959, with the steelwork of the Yapp Dome in place by the end of March 1960. Meanwhile, the rest of the building at Greenwich was demolished in 1959 along with the other buildings in the Christie Enclosure. The Yapp telescope itself, was dismantled towards the end of 1955 prior to its move to Herstmonceux. The Elizabeth telescope has since been moved to Sutherland.


Image licensing

The two photographic images on this page are © BT Heritage. They have been obtained from The BT Digital Archives and are reproduced under the terms of a Creative Commons Attribution-Non-Commercial-ShareAlike (CC BY-NC-SA) licence. They are more compressed than the originals.