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Dún Sinche
Dunsink Observatory
Dunsink is located in Ireland
Location in Ireland
Coordinates: 53°23′14″N 6°20′19″W / 53.387338°N 6.33849°W / 53.387338; -6.33849Coordinates: 53°23′14″N 6°20′19″W / 53.387338°N 6.33849°W / 53.387338; -6.33849
Country Ireland
Province Leinster
County Dublin
 • Local Authority Fingal County Council
 • Dáil Éireann Dublin North-West
Time zone WET (UTC+0)
 • Summer (DST) IST (WEST) (UTC-1)

Dunsink (Irish: Dún Sinche, meaning "Fort of Sinneach") is a townland in the civil parish of Castleknock, Dublin, in Ireland.[1] It is most famous for Dunsink Observatory where William Rowan Hamilton and Hermann Brück were directors. It is the oldest scientific institution in Ireland. Built in 1783-1785, the observatory houses a 12-inch (30 cm) refracting telescope which was built by Grubbs of Dublin using a French manufactured lens.

The 1880 Definition of Time Act set the official time in Ireland to be Dublin mean time. This was regarded to mean the time at Dunsink, which was about GMT-25m21. In 1916 another Act moved Ireland to Greenwich Mean Time. Dunsink time is mentioned five times in James Joyce's novel, Ulysses.

The observatory is situated on a hill 8 km northwest of Dublin's city centre, where the Astronomy section of the School of Cosmic Physics in the Dublin Institute for Advanced Studies is located.

Dunsink is also the site of a major unofficial Traveller encampment, the subject of considerable media coverage in 2007.


  1. ^ Placenames Database of Ireland - Dunsink townland.

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