By Rebekah Higgitt

Aerial photography of the Royal Observatory, Greenwich

Aerial photography of the Royal Observatory, Greenwich. © National Maritime Museum.

The Royal Observatory Greenwich (ROG) is part of Royal Museums Greenwich, also comprising the National Maritime Museum (NMM), The Queen’s House and Cutty Sark. Each reveals the royal and maritime influences on Greenwich, and each has elements of interest to historians of science. The buildings, dating from the 17th to 19th centuries, with many more recent additions and alterations, border and are contained within a Royal Park and the Maritime Greenwich World Heritage Site.

The science associated with Greenwich was very largely done for maritime purposes. It was practical, utilitarian and concerned with precision, accuracy and standards rather than the production of new knowledge. Few scientific discoveries can be associated with the Observatory, but its importance to the history of astronomy, timekeeping, navigation and cartography is demonstrated by the fact that, ultimately, the world’s standard reference point for time and position – the Prime Meridian – came to be the meridian on which the ROG’s chief instrument was set.

The Royal Observatory was founded in 1675 with the remit of improving astronomical tables in order to aid maritime navigation, specifically to support the lunar distance method for finding longitude (east-west position). Predicting the motions of the moon turned out to be an even harder problem than anticipated, and it was not until the 1760s that the ROG fulfilled its remit, when observations began to feed into the Nautical Almanac.

A complementary method of finding longitude at sea, using a timekeeper that could keep time at a regular rate over the course of a long voyage, matured at the same time. Once sea watches, or chronometers, became sufficiently numerous and affordable, the Astronomer Royal was charged with testing, rating and distributing them for the Royal Navy. Thus both the astronomical and timekeeping methods of finding longitude were supported by the work of the Observatory.

The ROG was a leading institution in the development of precision, meridian astronomy. The Astronomers Royal commissioned London’s top instrument and clock makers, the Observatory’s equipment and routines were hugely influential and its output was generally accepted as the most thorough and reliable. The work of John Flamsteed, James Bradley and Nevil Maskelyne was seen as core to Britain’s reputation in practical astronomy.

In the 19th century work at the ROG began to diversify. Magnetic and meteorological observations were begun, the distribution of time for civilian purposes became increasingly important and new techniques, particularly photography and spectroscopy, were introduced. Despite some new research, Greenwich largely focused on providing services for navigation and astronomy and on long-term programmes of data collection.

The buildings of the ROG, much extended and altered over the years, reveal this history. The oldest is Flamsteed House, the first floor and basement of which was home to the Astronomers Royal and their families until the institution moved to Herstmonceux in Sussex after the Second World War. On the first floor is the Octagon Room, built to house and test the going of Thomas Tompion’s experimental clocks, but thereafter largely used for storage and as a meeting room.

The real observatory was the series of buildings that housed the meridian instruments. Flamsteed’s original meridian observatory, which housed his mural arc, was built over several times, so the series of buildings that exists today is that begun by Bradley in the 1740s to house the quadrants, transit telescope, clocks and assistant astronomer. These buildings were extended several times as new instruments and additional work space was required. Some additions were removed when the Observatory was transformed into a Museum in the 1960s.

Greenwich Observatory

Greenwich Observatory by heatheronhertravels. Image licensed under Creative Commons Attribution-NoDerivs 2.0 Generic license.

Many of the original instruments of the Observatory survive and have been set up largely in their original locations, providing a timeline toward the Airy Transit Circle (1851), which defined the international Prime Meridian.

Adjoining the meridian buildings is the Great Equatorial Building (1857), today housing the second of the two large equatorial telescopes that were mounted there in the 19th century. It marks a clear development of the Observatory’s work away from an exclusive focus on meridian astronomy. Below the telescope are rooms in which the Navy’s chronometers were tested and stored. Today they contain the office and workshop (visible through a glass wall) of the Museum’s horologists.

The Observatory’s site continues southwards from here, towards an area added in the 1830s. Until the end of the century, this contained the Magnetic Observatory, which was later moved out into an enclosure within Greenwich Park and, in the 1920s, to Abinger. The buildings that remain date from the 1890s: the Altazimuth Pavilion, originally containing an altazimuth telescope, and the South Building. Originally called the New Physical Observatory, this housed three large telescopes, darkrooms, record and instrument stores, workshop and the office space for a much enlarged staff.

Today, the displays at the ROG fall into three categories. Firstly, the Astronomer’s Apartments and the Octagon Room in Flamsteed House have been dressed to suggest their original 17th-century appearance, while the Meridian Building displays the remounted 18th- and 19th-century instruments. Secondly, there are galleries that focus on the history of timekeeping: the story of longitude, the Navy’s chronometers, the dissemination of Greenwich Mean Time, and personal timekeeping. Thirdly, the South Building houses galleries dedicated to interactive exhibits and modern astronomy and adjoins a purpose-built planetarium.

As well as many of the Observatory’s original instruments, the ROG’s displays benefit from astronomical, navigational and cartographic collections acquired by the NMM from the 1930s onward. Descriptions of all objects and artworks in the collections are available online. The archives of the ROG itself are now held at Cambridge (which is where the institution ended up before its closure in 1998) but the Museum’s Caird Library and Archive contain relevant books and manuscripts, including the Airy Collection of rare books formerly belonging to the Observatory.

Further reading

A brief introduction to the history of the ROG can be found on its website, but the most thorough history is the three volumes by Eric G. Forbes, A. J. Meadows and Derek Howse: Greenwich Observatory. Howse is also author of the very useful Greenwich Time and Longitude. For an illustrated snapshot of what the Observatory was like at the end of the 19th century see E. Walter Maunder’s The Royal Observatory, Greenwich: a Glance at its History and Work.

There are four important catalogues showcasing some of the most significant scientific instrument collections: Astrolabes, Sundials, Globes and Sextants. A fifth, dedicated to Chronometers, is in progress.