The Magnetic and South Grounds

By the 1940s, the Observatory’s main site at Greenwich occupied an area of 2.46 acres. This section deals only with the Magnetic and South Grounds. Other parts of the grounds are covered in the following sections:

The Courtyard
The Astronomers’ Garden
The Meridian Garden
The Garden to the west of Flamsteed House
The Observatory Garden (now part of the Royal Park)
The Christie Enclosure (now part of the Royal Park)



Magnetic Ground and South Ground are the names originally given to the more or less level area located south of the Great Equatorial Building (28-inch Telescope Dome). Today they are occupied by the New Physical Building (South Building), the Altazimuth Pavilion, the Peter Harrison Planetarium and the Park Toilets.

The Magnetic Ground, the most northerly part, was enclosed in 1837 to enable Airy to build his Magnetic Observatory. The enclosure was extended southwards by Royal Warrant in December 1868 in anticipation of future needs, the newly enclosed section becoming known as the South Ground. The South Ground was extended westwards by Royal Warrant in November 1907 to allow for the building of the Lower Store (now the Park Toilets).


The direction of slope

Originally the land sloped gently towards the south, the slope being greatest in the recently enclosed South Ground. To make the land more useful in the short term, Airy had the south Ground roughly levelled into two terraces which ran east-west across the site. These were subsequently removed during the construction of the South Building. When the South Building was converted for gallery use by the National Maritime Museum in 2005/7, the slope was reversed in order to eliminate the steps up to the front door and provide direct wheel chair access to the building. This change of slope is most clearly visible along the boundary with Blackheath Avenue.


Past and present buildings

Initially the Magnetic Ground was home to the Magnetic and Meteorological Observatories along with two small yards for the Gardener and Carpenter. With pressure on space, other buildings soon started to appear. A small transit pavilion in 1843/4 (‘Struve’s Observatory’), a large open shed with a slated roof in 1851, a range of seven wooden magnetic offices in 1862 and the rather grandly named Depôt for publications in 1868 (a glorified wooden shed). After the South Ground was enclose at the end of 1868, the large shed (now renamed as the Great Shed) and Depôt were moved to the new southern boundary. In the early 1870s, the south ground was cluttered with various small wooden huts that had been purchased for the forthcoming Transit of Venus expedition in 1874.

The New Library was built in 1881 and the Lassell Dome in 1884. The Lassell Dome was demolished 11 years later to make way for the South Building which was erected between 1891 and 1899. While this was being built, the Altazimuth Pavilion was erected in 1896.

Since the 1870s, the South Ground had been cluttered with huts and stores and part of the reason for building the South Building was to enable them all to be cleared away. Those that occupied the space needed for its east and west wings were demolished. The Magnetic Offices, which occupied the space needed for the north wing, were relocated. 

The Great Shed and Depôt for publications were both demolished in about 1900 after the South Building had been completed. However, the Observatory was still short of storage space. To remedy this, the land to the west of the south building was enclosed in 1907 to enable the building of the Lower Store (now the toilets in the Park). The Magnetic Observatory was demolished in 1918 at the end of the WW1 and the area grassed over. Parts of the Altazimuth and South Buildings were destroyed by bombs that fell during the Blitz on the night of 21 October 1940, as were parts of the Magnetic Offices, which by then were variously in use as garages, stables and a store.


The National Maritime Museum takes over part of the area

A new Royal Warrant drawn up in 1953 as the working Observatory was in the throws of moving to Herstmonceux It assigned the Magnetic and South Grounds to the Royal Parks, who planned to demolish all the buildings except the Altazimuth Pavilion which it was proposed to convert into a park shelter and the Lower Store which it planned to turn into public toilets. By 1958, the National Maritime Museum had started squatting in the South Building which probably helped secure its preservation. It was converted for Museum use along with the Altazimuth Pavilion in the early 1960s. The James Caird planetarium opened in the dome at the top of the South Building in 1965. Meanwhile, the Lower Store conversion had gone ahead and the remaining buildings demolished.


A new planetarium

With the dawn of the new Millennium, the National Maritime Museum under its Director, Roy Clare, began evolving serious plans to create a new planetarium with better access, and to bring the South Building into gallery use. To facilitate this, the boundary was shifted slightly westwards both adjacent to where the new planetarium was to be built and along the narrow pathway that connected the Magnetic and South Grounds to the northern end of the Observatory site.

The external shape of the new planetarium – a truncated cone – was conceived by Robin Catchpole and designed by the architectural practice of Allies and Morrison. It was they who were responsible for the hard landscaping around the cone, which was designed to emphasize its clean lines. It does this at the expense of the Altazimuth Pavilion, which has lost the context of its traditional garden setting and has the unfortunate appearance of being marooned at the bottom of the slope. The new planetarium and galleries (The Astronomy Centre) were opened by the Queen on 22 May 2007.

Although it was known that the bronze cladding of the cone had the potential to get dangerously hot in sunny weather, a mechanism for dealing with this was not built into the original design. Initially, the problem was dealt with on an ad hoc basis by the use of tensabarriers. The National Maritime Museum installed the current bespoke removable barrier in 2010.