Kew Observatory

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Kew Observatory
Location Old Deer Park, Richmond, London, United Kingdom
Coordinates 51°28′08″N 0°18′53″W / 51.4689°N 0.3147°W / 51.4689; -0.3147Coordinates: 51°28′08″N 0°18′53″W / 51.4689°N 0.3147°W / 51.4689; -0.3147
Established 1769

Kew Observatory,[1] also known as the King's Observatory, was an astronomical and terrestrial magnetic observatory[2] founded by King George III. The building, which is Grade I listed,[3] was completed in 1769,[4] in time for the king's observation of the transit of Venus that occurred on 3 June in that year. A contemporary report by Stephen Demainbray, the superintendent of the observatory, says: "His Majesty the King who made his observation with a shorter reflecting telescope, magnifying Diameter 170 Times was the first to view the Penumbra of Venus touching the Edge of the Sun's Disk. The exact mean time (according to civil Reckoning) was attended to by Stephen Demainbray, appointed to take exact time by Shelton's Regulator, previously regulated by several astronomical observations."[5]

In 1985 the observatory was refurbished and transformed into commercial offices. Since then the building and its four-acre plot have been privately owned.


The observatory is located within the Old Deer Park of the former Richmond Palace in Richmond, Surrey, now within Greater London. The former royal manor of Kew lies to the immediate north. The observatory grounds overlie to the south the site of the former Carthusian Sheen Priory established by King Henry V in 1414.[6]


The architect was Sir William Chambers. The Chippendale-Chinese woodwork inside the octagons is by James Arrow. The three obelisks close to the observatory are by Edward Anderson.[4]


The Kew Observatory participated in assessing and rating chronometers, watches, barometers, thermometers, sextants and other scientific instruments for accuracy until this duty was transferred to the National Physical Laboratory in 1910. An instrument which passed the tests was awarded a "Kew Certificate", a hallmark of excellence.

As marine navigation adopted the use of mechanical timepieces, their accuracy became more important. The need for precision resulted in the development of a testing regime involving various astronomical observatories. In Europe, the observatories at Neuchatel, Geneva, Besancon and Kew were examples of prominent observatories that tested timepiece movements for accuracy. The testing process lasted for many days, typically 45. Each movement was tested in five positions and two temperatures, in ten series of four or five days each. The tolerances for error were much finer than any other standard, including the modern COSC standard. Movements that passed the stringent tests were issued a certification from the observatory called a Bulletin de Marche, signed by the directeur of the observatory. The Bulletin de Marche stated the testing criteria and the actual performance of the movement. A movement with a Bulletin de Marche from an observatory became known as an Observatory Chronometer, and was issued a chronometer reference number by the observatory.

The role of the observatories in assessing the accuracy of mechanical timepieces was instrumental in driving the mechanical watchmaking industry toward higher and higher levels of accuracy. As a result, modern high quality mechanical watch movements have an extremely high degree of accuracy. However, no mechanical movement could ultimately compare to the accuracy of a quartz movement. Accordingly, such chronometer certification ceased in the late 1960s and early 1970s with the advent of the quartz watch movement.


Directors (superintendents) of the observatory included Stephen Demainbray, John Welsh, Balfour Stewart, G. M. Whipple, Francis John Welsh Whipple, Charles Chree, and George Clarke Simpson.

Kew Observatory in art[edit]

The Ashmolean Museum of Art and Archaeology in Oxford has a portrait, Peter Rigaud and Mary Anne Rigaud, by the eighteenth-century painter John Francis Rigaud. His portrait of his nephew and niece, exhibited at the Royal Academy in 1778, shows Stephen Peter Rigaud (1774–1839) (who became a mathematical historian and astronomer, and Savilian Chair of Geometry and Savilian Professor of Astronomy at the University of Oxford) and his elder sister. In the picture, painted when they were aged four and seven, they are playfully embracing each other in a park; the building in the background is Kew Observatory, where their father Stephen Rigaud, was observer.[7] Although described here as Richmond Park, topographical considerations make it more likely that the park portrayed is Old Deer Park, where the observatory is situated.

See also[edit]

Notes and references[edit]

  1. ^ Scott, Robert Henry (1885). "The History of the Kew Observatory" in Proceedings of the Royal Society, Vol. XXXIX. pp. 37–86. 
  2. ^ Hunt, Andrew (21 January 2007). "Where a king watched a transit of Venus". Cities of Science. Retrieved 8 March 2014. 
  3. ^ "Kew Observatory". National Heritage List for England. English Heritage. Retrieved 28 December 2013. 
  4. ^ a b Cherry, Bridget and Pevsner, Nikolaus (1983). The Buildings of England – London 2: South. London: Penguin Books. p. 520. ISBN 0 14 0710 47 7. 
  5. ^ Manuscript of Dr. Demainbray's notebook of the Transit of Venus 1769, "The Observatory: A Monthly Review of Astronomy" (1882) called 'Dr Demainbray and the King's Observatory at Kew'. The manuscript is now held at King's College London and is quoted in "The King's Observatory at Kew & The Transit of Venus 1769". Arcadian Times. Retrieved 4 August 2013. 
  6. ^ Cloake, John (1990). Richmond's Great Monastery, The Charterhouse of Jesus of Bethlehem of Shene (Paper no.6). London: Richmond Local History Society. p. 51. diagram 
  7. ^ "John Francis Rigaud (1742–1810): Stephen Peter Rigaud and Mary Anne Rigaud". Browse the Paintings Collection. Ashmolean Museum of Art and Archaeology. Retrieved 13 July 2013. 

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