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Dunsink Observatory

Dunsink Observatory
OrganizationDublin Institute for Advanced Studies (DIAS)
Observatory code 982 Edit this on Wikidata
LocationDunsink, Dublin, Ireland
Coordinates53°23′13″N 6°20′15″W / 53.38708°N 6.33756°W / 53.38708; -6.33756
WebsiteDunsink Observatory
South TelescopeRefracting (lens) telescope
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Dunsink Observatory

The Dunsink Observatory is an astronomical observatory established in 1785 in the townland of Dunsink in the outskirts of the city of Dublin, Ireland.[1]

Dunsink's most famous director was William Rowan Hamilton, who, amongst other things, discovered quaternions, the first non-commutative algebra form, while walking from the observatory to the city with his wife. The annual Hamilton Walk that commemorates this discovery begins at the observatory. He is also renowned for his Hamiltonian formulation of dynamics.


The observatory was established by an endowment of £3,000 in the will of Francis Andrews, who was Provost of Trinity College Dublin at his death on 18 June 1774. The site was established on the south slope of a low hill in the townland of Dunsink, 84m above sea level.[2] The South Telescope, a 12-inch Grubb instrument, is a refracting (i.e. it uses lens) telescope built by Thomas Grubb of Dublin and completed in 1868.[3] The achromatic lens, with an aperture of 11.75 inches, was donated by Sir James South in 1862, who had purchased the lens from Cauchoix of Paris 30 years earlier.[4] He had intended it for a large but troubled equatorial that came to fruition in the 1830s, but was dismantled around 1838.[5][6] (See also Great refractors)

The entry for the observatory in Thom's Directory (1850) gives the following account of the observatory,


Astronomer Royal, Sir William Rowan Hamilton, A.M., LL.D.
Assistant Astronomer, Charles Thomson, esq.

This Observatory, endowed by Francis Andrews, esq., LL.D., Provost of Trinity College, and erected in 1785, was placed, by statute, in 1791, under the management of the "Royal Astronomer of Ireland," an appointment first filled by Dr. Henry Ussher, and subsequently by Dr. Brinkley, Bishop of Cloyne.

The Institution is amply furnished with astronomical instruments, and is open to all persons interested in astronomical science, on introduction to the resident Assistant. It is situated in Lat. 53° 23' 13" N., Long. 6° 20' 15" W.[1]

Dublin Mean Time, the official time in Ireland from 1880, was the local mean time at Dunsink, just as Greenwich Mean Time (GMT) is the local mean time at Greenwich Royal Observatory near London.[7] In 1916, Ireland moved to GMT. In 1936, Trinity College stopped maintaining the observatory and rented out the land.

Éamon de Valera, who had driven the establishment of the Dublin Institute for Advanced Studies (DIAS) in 1940, added a School of Cosmic Physics to it in 1947, partly in order to revive the observatory, for which it was given responsibility.

The named chair Andrews Professorship of Astronomy was associated with the directorship of Dunsink Observatory during the time that the observatory was part of Trinity College Dublin (TCD).

By the late 20th century, the city encroached ever more on the observatory, which compromised the seeing. The telescope, no longer "state of the art", is now used mainly for public 'open nights'.

The observatory is currently part of the DIAS. It provides accommodation for visiting scientists and is also used for conferences and public outreach events. Public talks on astronomy and astrophysics are given regularly at the observatory by professional and amateur astronomers. Stargazing events are also held using the Grubb telescope.

Directors of the observatory

Dates Name Other titles Notes
1783–1790 Rev. Henry Ussher Andrews Professor of Astronomy Died in office
1792–1827 Rev. John Brinkley Andrews Professor of Astronomy, Royal Astronomer of Ireland (from 1793) Appointed Bishop of Cloyne in 1826
1827–1865 Sir William Rowan Hamilton Andrews Professor of Astronomy, Royal Astronomer of Ireland Appointed as a 21-year-old undergraduate. In addition to astronomy, he worked on mathematics. He developed what is now known as Hamiltonian mechanics, and the system of quaternions, having discovered them in 1843. He died in office.
1865–1874 Franz Brünnow Andrews Professor of Astronomy, Royal Astronomer of Ireland Retired due to failing health and eyesight
1874–1892 Sir Robert Stawell Ball Andrews Professor of Astronomy, Royal Astronomer of Ireland In 1892 became Lowndean Professor of Astronomy and Geometry at Cambridge
1892–1897 Arthur Alcock Rambaut Andrews Professor of Astronomy, Royal Astronomer of Ireland In 1897 became Radcliffe Observer at Oxford
1897–1906 Charles Jasper Joly Andrews Professor of Astronomy, Royal Astronomer of Ireland Died in office
1906–1912 Sir Edmund Taylor Whittaker Andrews Professor of Astronomy, Royal Astronomer of Ireland In 1911 became a professor at Edinburgh
1912–1921 Henry Crozier Keating Plummer Andrews Professor of Astronomy, Royal Astronomer of Ireland In 1921 became professor of mathematics at the Artillery College in Woolwich
1921–1936 Charles Martin Acting Director, assisted by F J O'Connor (1908-1987). Died in office
1936–1947 Vacant   No astronomical work was done
1947–1957 Hermann Alexander Brück Director of DIAS School of Cosmic Physics In 1957 became Astronomer Royal for Scotland
1958–1963 Mervyn Archdall Ellison Director of DIAS School of Cosmic Physics Died in office
1964–1992 Patrick Arthur Wayman Andrews Professor of Astronomy (from 1984, honorary), Director of DIAS School of Cosmic Physics Retired, with a short gap before the next appointment.
1994–2007 Evert Meurs Senior Professor DIAS Retired
2007–2018 Luke Drury Andrews Professor of Astronomy (honorary), Director of DIAS School of Cosmic Physics Retired
2018–present Peter T. Gallagher Senior Professor and Head of Astronomy and Astrophysics, DIAS

In fiction

The observatory is one of the locations featured in the book, The Coroner's Daughter by Andrew Hughes, which was selected as the Dublin UNESCO City of Literature One City One Book for 2023.[8]

See also



  • "The Andrews Professor of Astronomy of Astronomy (1783)". School of Physics. Trinity College Dublin. Retrieved 26 September 2017.
  • Wayman, P. A. (March 1986). "The Andrews' Professors of Astronomy and Dunsink Observatory, 1785–1985". Irish Astronomical Journal. 17 (3): 167–183. Bibcode:1986IrAJ...17..167W.


  1. ^ a b Alexander Thom, Irish Almanac and Official Directory 7th ed., 1850 p. 258. Retrieved: 2011-02-22.
  2. ^ Ordnance Survey Map Archived 2012-08-29 at the Wayback Machine. Select Wind Report for elevation. Retrieved: 2011-02-22.
  3. ^ The South Telescope of Dunsink Observatory Authors: Wayman, P. A. Journal: Irish Astronomical Journal, vol. 8(8), p. 274 Bibliographic Code: 1968IrAJ....8..274W
  4. ^ History of the Cauchoix objective
  5. ^ "The Observatory of the Late Sir James South". Astronomical Register. 8: 196–199. 1870. Bibcode:1870AReg....8..196.
  6. ^ Dictionary of National Biography, 1885-1900, Volume 53, "South, James", by Agnes Mary Clerke (WikiSource 2010)
  7. ^ Dyson, F. W. (1916). "Standard time in Ireland". The Observatory. 39 (3): 467–468.
  8. ^ Halpin, Hayley (12 October 2022). "A mystery novel set during 1816 chosen as the 2023 One Dublin One Book". Retrieved 15 October 2022.
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Dunsink Observatory
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