List of largest optical telescopes in the British Isles


List of largest optical telescopes in Ireland and the United Kingdom is a list of the largest optical telescopes in the British Isles, including in the United Kingdom and Ireland.

The 28-inch Grubb refractor's dome at Greenwich.
Discovered as Georgium Sidus, later known as Uranus was one of the famous discoveries made from the British Isles
The mirror from the 40-foot telescope, on display at the Science Museum, London.
Former Royal Greenwich Observatory, Herstmonceux, East Sussex; this was an important site for telescopes in the latter 20th century in England.
Closeup of lower end of a 28-inch aperture telescope
The Leviathan, 1885
The old INT dome

Some of the most famous telescopes would be Herschel's reflector, which he discovered Georgium Sidus, the Leviathan of Parsontown which at 1.8 meters (72 inches) was for decades the largest aperture telescope in the World, and in the 20th century many older telescopes are popular tourist attractions such as at Royal Observatory in Greenwich, London. There is also number of modest instruments at universities used for various astronomical projects or education.

The biggest optical telescope was the Isaac Newton Telescope at Herstmonceux, with a 98 inch mirror (~249 cm); it was there from 1965 to 1980; a lot of astronomy moved to off-site telescopes in space or distant mountains, with data transmitted electronically. The void left for public outreach is filled in part by planetariums and various museum pieces.

The list is not really representative of the largest telescopes operated by the United Kingdom or Ireland, which by the 20th century were building large telescopes overseas or in the southern hemisphere for better weather or other reasons.

Current listEdit

The following is a non-comprehensive list of optical telescopes currently located in the British Isles with an aperture of 24" or greater:

Reflecting telescopes
Name Effective aperture Type Location Operator First light Comments
Rosse Six Foot Telescope (reconstructed) [1] 72 in (183 cm) Newtonian reflector Birr, Leinster, Ireland Birr Castle 1999 Largest optical telescope in the British Isles
The 38-inch Congo Schmidt [2] 38 in (96.5 cm) Reflector Herstmonceux, East Sussex, England The Observatory Science Centre 1960 Largest optical telescope in UK, but never used due to flawed optics
James Gregory Telescope[3] 37 in (94.0 cm) Cassegrain reflector St Andrews, Fife, Scotland University of St Andrews 1962 Largest operational optical telescope in the UK
36-Inch Telescope [4] 36 in (91.4 cm) Reflector Cambridge, Cambridgeshire, England University of Cambridge 1955 Largest optical telescope still in use in England
The 36-inch Yapp Reflector [5] 36 in (91.4 cm) Reflector Herstmonceux, East Sussex, England The Observatory Science Centre 1932
The 36-inch telescope [6] 36 in (91.4 cm) Reflector Edinburgh, Scotland Royal Observatory Edinburgh 1930 No longer operational
The 34-inch Hewitt Camera [7] 34 in (86.4 cm) Reflector Herstmonceux, East Sussex, England The Observatory Science Centre 1950s
Perren Telescope [8] 31.5 in (80.0 cm) Ritchey–Chrétien reflector Mill Hill, London, England University College London 2019
John Wall refractor [9] 30 in (76.2 cm) Refractor Hanwell, Middlesex, England Hanwell Community Observatory 1999 Largest refractor in the British Isles
30" Dobsonian [10] 30 in (76.2 cm) Reflector Todmorden, West Yorkshire, England The Astronomy Centre 1986
The Thompson 30-inch Reflector [11] 30 in (76.2 cm) Reflector Herstmonceux, East Sussex, England The Observatory Science Centre 1896
Greenwich 28 inch refractor[12] 28 in (71.1 cm) Refractor Greenwich, London, England Royal Observatory, Greenwich 1893
Moses Holden Telescope [13] 27.6 in (70.1 cm) Reflector Preston, Lancashire, England University of Central Lancashire 2015
The Thompson 26-inch Refractor [14] 26 in (66.0 cm) Refractor Herstmonceux, East Sussex, England The Observatory Science Centre 1897
24 / 17" Schmidt Camera [15] 24 in (61.0 cm) Reflector Knighton, Powys, Wales The Spaceguard Centre 1950 Largest optical telescope in Wales
Thornton Telescope [16] 24 in (61.0 cm) Reflector Keele, Staffordshire, England Keele University 1975
24" Telescope [17] 24 in (61.0 cm) Reflector Bayfordbury, Hertfordshire, England University of Hertfordshire 2021


  • Isaac Newton Telescope at Herstmonceux, 98 inches (1965-1979)
  • Leviathan of Parsonstown, 1842- ~1890
  • 3-foot telescope at Parsons
  • RGO telescopes at different points in its history[18]
    • 38-inch Hargreaves Reflector (1960)
    • Yapp 36-inch Reflector (1932)
    • 30-inch Steavenson Reflector (1939)
    • 28-inch Refractor (1893)
    • Thompson Telescope with a 26-inch refractor and 30-inch reflector on one mounting (1896)
    • Lassell 2-foot Reflector (1845)
    • Isaac Roberts 20-inch reflector (1885)
    • Western Equatorial (c.1824)
    • 13-inch Astrographic Refractor (1890)
    • Merz 12.8-inch Visual Refractor (1859-1893) (this was replaced by the 28 inch Grubb in the onion dome)
    • Thomson 9-inch Photographic Refractor (c.1888)
    • Sheepshanks refractor 6.7-inch (1838) (aka Sheepshanks Equatorial)
    • 6-inch Franklin Adams Camera (1898)
    • Shuckburgh telescope a 4.1-inch aperture Refractor (1791)
  • At the Observatory Science Center (at Herstmonceux)[19]
  • Markree Observatory 13.3" Cauchoix (the largest refractor of the early 1830s)
  • A.A. Commons reflectors (later reworked into Crossley and Harvard telescopes)
  • Lassel's reflector, this 24 inch metal mirror telescope was used to discover the moon's Triton and Hyperion.[20]
  • Newton's reflector
  • 40-foot telescope (England)
  • Armagh Observatory 15-inch Grubb reflecting telescope.[21] Specula metal mirror mounted on an equatorial, with clockwork-drive.[21]
  • Bedford Observatory Tully 5.9 inch refractor (8.5 feet focal length); Dollond mount with Sheepshanks clockwork drive.[22]
  • Cambridge Observatory 36 inch (3 foot ~91.44 cm) aperture reflector


A noted accomplishment of the biggest telescope at the time, Ross's "six foot" leviathan, was the observation of the spiral structure of M51, which was presented at Cambridge in the summer of 1845.[23] Herschel was quite prolific discovering a planet and many moons of the Solar system also with his reflectors.

See alsoEdit


  1. ^ "The Great Telescope at Birr Castle | Birr Castle, Gardens & Science Centre | Ireland".
  2. ^ "The 38-inch Congo Schmidt".
  3. ^ "JGT – Observatory".
  4. ^ "36-Inch Telescope | Institute of Astronomy".
  5. ^ "The 36-inch Yapp Reflector".
  6. ^ "The Royal observatory, Edinburgh".
  7. ^ "The 34-inch Hewitt Camera".
  8. ^ "Perren Telescope". 29 October 2018.
  9. ^ "John Wall refractor | Hanwell Community Observatory".
  10. ^ "The rebuilt 30" Dobsonian".
  11. ^ "Dome A - the Thompson 30-inch reflecting telescope".
  12. ^ Wright, D. C. (1990). "The 28-inch Refractor at Greenwich - a History of Two Telescopes". Quarterly Journal of the Royal Astronomical Society. Royal Astronomical Society. 31 (4): 551–566. Bibcode:1990QJRAS..31..551W.
  13. ^ "Alston Observatory – Jeremiah Horrocks Institute".
  14. ^ "Dome e - the Thompson 26-inch refracting telescope".
  15. ^ "Project DRAX in Detail | the Spaceguard Centre".
  16. ^ "1970s, Keele University".
  17. ^ "Telescopes".
  18. ^ "Telescopes".
  19. ^ "Observatory Science Centre at Herstmonceux". Retrieved 2019-10-27.
  20. ^ "The Royal Observatory Greenwich - where east meets west: Telescope: The Lassell 2-foot Reflector (1847)". Retrieved 2019-11-28.
  21. ^ a b Butler, C.J. "The 15-inch Equatorial Reflector by Thomas Grubb at Armagh Observatory".{{cite web}}: CS1 maint: url-status (link)
  22. ^ "1949PA.....57...74K Page 74". Bibcode:1949PA.....57...74K. Retrieved 2019-10-31.
  23. ^ Information, Reed Business (1983-08-04). New Scientist. Reed Business Information.

External linksEdit

  • The 98 inch (249 cm) mirror glass of original INT