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List of largest optical reflecting telescopes

This list of the largest optical reflecting telescopes with objective diameters of 3.0 metres (120 in) or greater is sorted by aperture, which is one limit on the light-gathering power and resolution of a reflecting telescope's optical assembly. The mirrors themselves can be larger than the aperture, and telescopes may use aperture synthesis achieved by interferometry. Telescopes designed to be used as optical astronomical interferometers such as the Keck I and II used together as the Keck Interferometer (up to 85 m) can reach very high resolutions, although at a narrower range of observations. When the two mirrors are on one mount, the combined mirror spacing of the Large Binocular Telescope (22.8 m) allows fuller use of the aperture synthesis.

Gran Telescopio Canarias, Canary IslandsKeck Telescope (two units), HawaiiSubaru Telescope, Hawaii
Hobby–Eberly Telescope, TexasLarge Binocular Telescope, ArizonaVery Large Telescope (four units), Chile
Southern African Large TelescopeGemini North Observatory, HawaiiGemini South Observatory, Chile
The world's largest optical reflecting telescopes with an aperture diameter of larger than 8 meters (hover with mouse over image).

GTC · Keck · Subaru
SALT · Gemini (N) · Gemini (S)

Largest does not always equate to being the best telescopes, and overall light gathering power of the optical system can be a poor measure of a telescope's performance. Space-based telescopes, such as the Hubble Space Telescope, take advantage of being above the Earth's atmosphere to reach higher resolution and greater light gathering through longer exposure time. Location in the northern or southern hemisphere of the Earth can also limit what part of the sky can be observed.


Table of reflecting telescopesEdit

This list is ordered by optical aperture, which has historically been a useful gauge of limiting resolution, optical area, physical size, and cost. Multiple mirror telescopes that are on the same mount, may have a working beam combiner, and can form an image may be ranked by an equivalent aperture to this reported by sources. HET-style or fixed telescopes are ranked by an equivalent aperture also.

Reflecting telescopes
Name Image Effective aperture Mirror type Nationality / Sponsors Site Built
Gran Telescopio Canarias (GTC)   10.4 m (409 in) Segmented, 36 Spain (90%), Mexico, USA Roque de los Muchachos Obs., Canary Islands, Spain 2006/9
Hobby-Eberly Telescope (HET)
11 m × 9.8 m mirror
  10 m (394 in) [1] Segmented, 91 USA, Germany McDonald Observatory, Texas, USA 1997
Keck 1   10 m (394 in) Segmented, 36 USA Mauna Kea Observatories, Hawaii, USA 1993
Keck 2   10 m (394 in) Segmented, 36 USA Mauna Kea Observatories, Hawaii, USA 1996
Southern African Large Telescope (SALT)
11 m × 9.8 m mirror[2]
  9.2 m (362 in) Segmented, 91 South Africa, USA, UK, Germany, Poland, New Zealand South African Astronomical Obs., Northern Cape, South Africa 2005
Large Binocular Telescope (LBT)
Phased-array optics for combined 11.9 m[3]
  8.4 m (331 in) × 2 Multiple mirror, 2 USA, Italy, Germany Mount Graham International Observatory, Arizona, USA 2004
Subaru (JNLT)   8.2 m (323 in) Single Japan Mauna Kea Observatories, Hawaii, USA 1999
VLT UT1 – Antu   8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 1998
VLT UT2 – Kueyen   8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 1999
VLT UT3 – Melipal   8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2000
VLT UT4 – Yepun   8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2001
Gemini North (Gillett)   8.1 m (319 in) Single USA, UK, Canada, Chile, Australia, Argentina, Brazil Mauna Kea Observatories, Hawaii, USA 1999
Gemini South   8.1 m (319 in) Single USA, UK, Canada, Chile, Australia, Argentina, Brazil Cerro Pachón (CTIO), Coquimbo Region, Chile 2001
MMT (1 x 6.5 m)   6.5 m (256 in) Single USA F. L. Whipple Obs., Arizona, USA 2000
Magellan 1 (Walter Baade)[4]   6.5 m (256 in) Honeycomb USA Las Campanas Obs., Atacama Region, Chile 2000
Magellan 2 (Landon Clay)   6.5 m (256 in) Honeycomb USA Las Campanas Obs., Atacama Region, Chile 2002
BTA-6   6 m (236 in) Single USSR/Russia Special Astrophysical Obs., Karachay–Cherkessia, Russia 1975
Large Zenith Telescope (LZT)   6 m (236 in) Liquid Canada, France, United States [5] Maple Ridge, British Columbia, Canada 2003
Hale Telescope (200 inch)   5.08 m (200 in) Single USA Palomar Observatory, California, USA 1948
LAMOST (6.67 m × 6.05 m + 5.72 m × 4.40 m corrector; effective aperture 3.6–4.9 m)   4.9 m (193 in) [6] Segmented
(37 + 24)[7]
PRC (China) Beijing Astronomical Obs., Xinglong, China 2008
MMT (original optics: 6 × 1.8 m)
→see above for current 6.5 m mirror
  4.7 m (185 in)
(6×1.8 m) [8]
Segmented, 6 USA F. L. Whipple Obs., Arizona, USA 1979–1998
Discovery Channel Telescope[9]   4.3 m (169 in) Single USA Lowell Observatory, Happy Jack, Arizona, USA 2012
William Herschel Telescope   4.2 m (165 in) Single UK, Netherlands, Spain Roque de los Muchachos Obs., Canary Islands, Spain 1987
SOAR   4.1 m (161 in) Single USA, Brazil Cerro Pachón (CTIO), Coquimbo Region, Chile 2002
VISTA   4.1 m (161 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2009
Victor M. Blanco Telescope   4 m (157 in) Single USA Cerro Tololo Inter-American Obs., Coquimbo Region, Chile 1976
Nicholas U. Mayall 4 m[10]   4 m (157 in) Single USA Kitt Peak National Obs., Arizona, USA 1973
Anglo-Australian Telescope (AAT)   3.89 m (153 in) Single Australia, UK Australian Astronomical Obs., New South Wales, Australia 1974
3.67 m AEOS Telescope (AEOS)   3.67 m (144 in) Single USA Air Force Maui Optical Station, Hawaii, USA 1996
3.6 m Devasthal Optical Telescope[11] (DOT)   3.6 m (142 in) Single India ARIES Devasthal Observatory, Nainital, India 2016
Telescopio Nazionale Galileo (TNG)   3.58 m (141 in) Single Italy Roque de los Muchachos Obs., Canary Islands, Spain 1997
New Technology Telescope (NTT)   3.58 m (141 in) Single ESO countries La Silla Observatory, Coquimbo Region, Chile 1989
Canada-France-Hawaii Telescope (CFHT)   3.58 m (141 in) Single Canada, France, USA Mauna Kea Observatories, Hawaii, USA 1979
ESO 3.6 m Telescope   3.57 m (141 in) Single ESO countries La Silla Observatory, Coquimbo Region, Chile 1977
MPI-CAHA 3.5 m[12]   3.5 m (138 in) Single West Germany, Spain Calar Alto Obs., Almería, Spain 1984
USAF Starfire 3.5 m [13]   3.5 m (138 in) Single USA Starfire Optical Range, New Mexico, USA 1994
WIYN Telescope   3.5 m (138 in) Single USA Kitt Peak National Obs., Arizona, USA 1994
Space Surveillance Telescope   3.5 m (138 in) Single USA White Sands Missile Range, New Mexico, USA 2011
Astrophysical Research Consortium (ARC)   3.48 m (137 in) Single USA Apache Point Obs., New Mexico, USA 1994
Shane Telescope   3.05 m (120 in) Single USA Lick Observatory, California, USA 1959
NASA Infrared Telescope Facility   3.0 m (118 in) Single USA Mauna Kea Observatory, Hawaii, USA 1979
retired, private[14]
  3 m (118 in) Liquid USA NASA Orbital Debris Obs., New Mexico, USA 1995–2002
For continuation of this list, see List of large optical reflecting telescopes

There are only a few sites capable of polishing the mirrors for these telescopes. SAGEM in France polished the four VLT mirrors, the two Gemini mirrors, and the 36 segments for GTC.[15] The Steward Observatory Mirror Lab cast and polished the two LBT mirrors, the two Magellan mirrors and the MMT replacement mirror. It is currently making the LSST primary mirror and the mirrors for the Giant Magellan Telescope.[16] The Keck segments were made by Schott AG. The SALT and LAMOST segments were cast and polished by LZOS.[17] The mirror for Subaru was cast by Corning and polished at Contraves Brashear Systems in Pennsylvania.[18]

This table does not include all the largest mirrors manufactured. The Steward Observatory Mirror Lab produced the 6.5-metre f/1.25 collimator used in the Large Optical Test and Integration Site of Lockheed Martin, used for vacuum optical testing of other telescopes.

Segmented mirrors are also referred to as mosaic mirrors. Single mirrors are also referred to monolithic mirrors, and can be sub-categorized in types, such as solid or honeycomb.

Comparison of nominal sizes of apertures of some notable optical telescopes
For the largest reflecting telescopes on the planet, the horizontal indicates the year built and the vertical direction indicates the size of the mirror measured in meters. Countries which contain several of these telescopes are color-coded for identification.

Chronological list of largest telescopesEdit

These telescopes were the largest in the world at the time of their construction.

Reflecting telescopes (chronologically)
Years Largest Name Out In Aperture (m) Area (m2) M1 Mirror Note Altitude (m)
2009–Present Gran Telescopio Canarias     10.4 74 36 × 1.9 m hexagons M1 mirror Segmented mirror 2267
1993–2009 Keck 1     10 76 [19] 36 × 1.8 m hexagons M1 mirror Segmented mirror, M1 f/1.75 4145
1976–1993 BTA-6     6 26 605 cm f/4 M1 mirror Mirror replaced twice 2070
1948–1976 Hale (200 inch)     5.1 508 cm f/3.3 M1 mirror Art deco dome 1713
1917–1948 Hooker (100 inch)   2.54 Also used for 1st optical interferometer 1742

For earlier top telescopes see List of largest optical telescopes historically

Future telescopesEdit

Sketch of the Messier 51 by William Parsons in 1845, later known as the Whirlpool Galaxy
Whirlpool Galaxy (M51A/B or NGC 5194/5) by NASA/ESA from Hubble Space Telescope in 2005

Below are selected telescopes that are still in the conceptual/proposed stage or still under construction.

Under construction or planned constructionEdit


See alsoEdit


  1. ^ "Upgraded Hobby-Eberly Telescope Sees First Light | McDonald Observatory". Retrieved 2016-07-29.
  2. ^ "Howstuffworks "10 Amazing Telescopes"". Archived from the original on December 22, 2008. Retrieved August 19, 2009.
  3. ^ SPIE 2006 in Orlando - Proceedings of SPIE conference 6267 on “Ground-based and Airborne Telescopes”, "The Large Binocular Telescope", John M. Hill, Richard F. Green and James H. Slagle
  4. ^ "The Carnegie Observatories – Magellan Telescopes". Carnegie Institution for Science. Retrieved 2017-05-24.
  5. ^ The Telescope, By Geoff Andersen, Page 165
  6. ^ [1] Archived July 22, 2011, at the Wayback Machine.
  7. ^ "LAMOST Homepage – Gallery". August 13, 2012. Retrieved January 6, 2018.
  8. ^ Dwayne DayMonday, May 11, 2009 (2009-05-11). "Mirrors in the dark". The Space Review. Retrieved 2012-01-03.
  9. ^ Lowell Observatory - 4.3-meter DCT
  10. ^ "The Mayall 4-Meter Telescope". February 27, 1973. Retrieved August 19, 2009.
  11. ^ Sagar, Ram; Brijesh Kumar; Amitesh Omar; A. K. Pandey (2012). "New optical telescope projects at Devasthal Observatory". Proceedings of the Society of Photo-Optical Instrumentation Engineers. 8444. arXiv:1304.2474. Bibcode:2012SPIE.8444E..1TS. doi:10.1117/12.925634.
  12. ^ "Max-Planck-Institut für Astronomie". July 20, 1994. Retrieved August 19, 2009.
  13. ^ John Pike. "Starfire". Retrieved August 19, 2009.
  14. ^ "NASA Orbital Debris Observatory". Retrieved August 19, 2009.
  15. ^ "Polissage Optique pour les Grands Instruments de la Physique et de l 'Astronomie" (PDF). Archived from the original (PDF) on 2012-04-26.
  16. ^ "Mirror Castings". Steward Observatory Mirror Lab.
  17. ^ "Large Optics Manufacturing in Large Optics Manufacturing in Lytkarino Optical Glass Factory, Russia" (PDF). Archived from the original (PDF) on 2012-04-26.
  18. ^ "SUBARU Telescope 8.3m Primary Mirror Finished".
  19. ^ "Keck Telescope Facts". Retrieved 2012-01-03.
  20. ^ "Groundbreaking for the E-ELT (eso1419 — Organisation Release)". ESO. 19 June 2014. Retrieved 3 January 2015.
  21. ^ Stewart, Burnett, Colin M., John (October 14, 2016). "Hawaii Supreme Court voids Thirty Meter Telescope permit". Oahu Publications. West Hawaii Today. Retrieved 19 December 2015.
  22. ^ "GMT – Overview". Retrieved 2017-05-24.
  23. ^ Amos, Jonathan (12 November 2015). "Giant Magellan Telescope: Super-scope project breaks ground". BBC News. Retrieved 2015-11-15.
  24. ^ "NASA Completes Webb Telescope Review, Commits to Launch in Early 2021". NASA. 27 June 2018. Retrieved 3 July 2018.
  25. ^ "International Liquid Mirror Telescope – Extragalactic Astrophysics and Space Observations". Retrieved August 19, 2009.
  26. ^ Universities in U.S. and Mexico Partner on Telescope Project. Arizona Public Media, 13 November 2017.
  27. ^ Rezaei,, Maryam (November 12, 2018). "پا گرفتن طرحی که در شرایط تحریم نباید پا می‌گرفت/قد کشیدن رصدخانه ملی از صفر تا ارتفاع ۳۶۰۰متری". ISNA. ISNA. Retrieved 12 November 2018.
  28. ^ "Introduction to the Chinese Giant Solar Telescope" (PDF).
  29. ^ Staff (29 August 2012). "China Exclusive: Scientists looking for site for giant solar telescope". Retrieved 8 December 2014.

Further readingEdit

  • "The Astronomical Scrapbook", Joseph Ashbrook, Sky Publishing Corporation 1984, ISBN 0-933346-24-7, o
  • "Giant Telescopes of the World", Sky and Telescope, August 2000.
  • "The History of the Telescope", Henry C. King. (1955)
  • "The Historical Growth of Telescope Aperture", René Racine, Publications of the Astronomical Society of the Pacific, 116
  • JRASC (1929) vol 23, p351
  • Sky&Telescope (April 1981) p303
  • Sky&Telescope (July 1993) vol 86, p 27-32
  • James H. Burge, 1993 Dissertation at UA, "Advanced Techniques for Measuring Primary Mirrors for Astronomical Telescopes"
  • Bell, R.M. and Robins, G.C. and Eugeni, C. and Cuzner, G. and Hutchison, S.B. and Baily, S.H. and Ceurden, B. and Hagen, J. and Kenagy, K. and Martin, H.M. and Tuell, M. and Ward, M. and West, S.C. (July 2008). "LOTIS at completion of Collimator integration". Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series. 7017. Bibcode:2008SPIE.7017E..0DB. doi:10.1117/12.791889.

External linksEdit