Astronomy:List of largest optical reflecting telescopes

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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 a measure of the light-gathering power and resolution of a reflecting telescope. The mirrors themselves can be larger than the aperture, and some telescopes may use aperture synthesis through 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 higher 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.

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 times. Location in the northern or southern hemisphere of the Earth can also limit what part of the sky can be observed, and climate conditions at the observatory site affect how often the telescope can be used each year.

The combination of large mirrors, locations selected for stable atmosphere and favorable climate conditions, and active optics and adaptive optics to correct for much of atmospheric turbulence allow the largest Earth based telescopes to reach higher resolution than the Hubble Space Telescope.[1] Another advantage of Earth based telescopes is the comparatively low cost of upgrading and replacing instruments.

Table of reflecting telescopes

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 and can form a single combined image are ranked by their equivalent aperture. Fixed altitude telescopes (e.g. HET) are also ranked by their equivalent aperture. All telescopes with an effective aperture of at least 3.00 metres (118 in) at visible or near-infrared wavelengths are included.

Reflecting telescopes
Name Image Effective aperture Mirror type Nationality / Sponsors Site First light
Large Binocular Telescope (LBT) LBT-Gebaeude.jpg 11.9 m (469 in) (combined)[2] Multiple
Two 8.4 m (331 in) mirrors
United States , Italy, Germany Mount Graham International Observatory, Arizona, USA 2004
Gran Telescopio Canarias (GTC) Grantelescopio.jpg 10.4 m (409 in) Segmented
36 hexagonal segments
Spain , Mexico, United States Roque de los Muchachos Obs., Canary Islands, Spain 2006
Hobby–Eberly Telescope (HET) HET Dome.jpg 10 m (394 in) (effective) [3] Segmented
91 × 1 m (39 in) hexagonal segments forming an 11 m × 9.8 m mirror
United States , Germany McDonald Observatory, Texas , USA 1997
Aperture increased 2015
Keck 1 KeckTelescopes-hi.png 10 m (394 in) Segmented
36 hexagonal segments
United States Mauna Kea Observatories, Hawaii, USA 1993
Keck 2 KeckTelescopes-hi.png 10 m (394 in) Segmented
36 hexagonal segments
United States Mauna Kea Observatories, Hawaii, USA 1996
Southern African Large Telescope (SALT) Southern African Large Telescope 720x576px.jpg 9.2 m (362 in) (effective)[4] Segmented
91 × 1 m (39 in) hexagonal segments forming an 11 m × 9.8 m mirror
South Africa , United States , United Kingdom , Germany, Poland , New Zealand South African Astronomical Obs., Northern Cape, South Africa 2005
Subaru (JNLT) MaunaKea Subaru.jpg 8.2 m (323 in) Single Japan Mauna Kea Observatories, Hawaii, USA 1999
VLT UT1 – Antu Paranal opendome.jpg 8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 1998
VLT UT2 – Kueyen UVES on UT2-KUEYEN.jpg 8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 1999
VLT UT3 – Melipal Paranal UT3 2008-01-04.jpg 8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2000
VLT UT4 – Yepun Cloaked in Stars.jpg 8.2 m (323 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2001
Gemini North (Gillett) Gemini Observatory at sunset.jpg 8.1 m (319 in) Single United States , United Kingdom , Canada, Chile , Australia, Argentina , Brazil Mauna Kea Observatories, Hawaii, USA 1999
Gemini South Gemini South 01.jpg 8.1 m (319 in) Single United States , United Kingdom , Canada, Chile , Australia, Argentina , Brazil Cerro Pachón (CTIO), Coquimbo Region, Chile 2001
James Webb Space Telescope JWST spacecraft model 3.png 6.5 m

(256 in)

Segmented
18 hexagonal segments
NASA, ESA, CSA Halo orbit around the Earth-Sun L2 Point 2022
MMT (current optics) MMT Observatory.jpg 6.5 m (256 in) Single United States F. L. Whipple Obs., Arizona, USA 2000
Magellan 1 (Walter Baade)[5] Magellan telescopes.jpg 6.5 m (256 in) Single United States Las Campanas Obs., Atacama Region, Chile 2000
Magellan 2 (Landon Clay) Magellan telescopes.jpg 6.5 m (256 in) Single United States Las Campanas Obs., Atacama Region, Chile 2002
BTA-6 Главная обсерватория.jpg 6 m (236 in) Single USSR/Russia Special Astrophysical Obs., Karachay–Cherkessia, Russia 1975
Large Zenith Telescope (LZT) 180724main 6-mMirror.jpg 6 m (236 in) Liquid Canada , France , United States [6] Maple Ridge, British Columbia, Canada 2003
Decommissioned 2016
Hale Telescope P200 Dome Open.jpg 5.08 m (200 in) Single United States Palomar Observatory, California , USA 1949
LAMOST LAMOST telescope org.jpg 4.9 m (193 in) (effective)[7] Segmented
37 segments for the 6.67 m × 6.05 m primary and 24 segments for the 5.72 m × 4.40 m corrector; effective aperture 3.6–4.9 m[8]
China Beijing Astronomical Obs., Xinglong, China 2008
MMT (original optics)
(see above for current version)
MMT Observatory.jpg 4.7 m (185 in) (combined)[9] Multiple
Six 1.8 m (71 in) mirrors
United States F. L. Whipple Obs., Arizona, USA 1979
Mirrors removed 1998
Lowell Discovery Telescope[10] The Dome of Discovery Channel Telecope.JPG 4.3 m (169 in) Single USA Lowell Observatory, Happy Jack, Arizona, USA 2012
William Herschel Telescope William herschel Telescope Dome.jpg 4.2 m (165 in) Single United Kingdom , Netherlands, Spain Roque de los Muchachos Obs., Canary Islands, Spain 1987
SOAR SOAR telescope at twlight.jpg 4.1 m (161 in) Single United States , Brazil Cerro Pachón (CTIO), Coquimbo Region, Chile 2002
VISTA File:VISTA at Paranal Eso0704b.tif 4.1 m (161 in) Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2009
Víctor M. Blanco Telescope 4m-Victor M. Blanco Telescope.jpg 4 m (157 in) Single United States Cerro Tololo Inter-American Obs., Coquimbo Region, Chile 1976
International Liquid Mirror Telescope 4 m (157 in) Liquid Belgium, Canada , India , Poland ARIES Devasthal Observatory, Nainital, India 2022
Nicholas U. Mayall 4 m[11] Kittpeakteliscope.JPG 4 m (157 in) Single United States Kitt Peak National Obs., Arizona, USA 1973
Daniel K. Inouye Solar Telescope Haleakala Observatory 2017.jpg 4 m (157 in) Single United States Haleakala Observatory, Hawaii, USA 2019
Anglo-Australian Telescope (AAT) Anglo-Australian Telescope dome.JPG 3.89 m (153 in) Single Australia, United Kingdom Australian Astronomical Obs., New South Wales, Australia 1974
United Kingdom Infrared Telescope (UKIRT) UKIRT at sunset (straightened).jpg 3.8 m (150 in) Single United Kingdom , United States Mauna Kea Observatories, Hawaii, USA 1979
3.67 m AEOS Telescope (AEOS) AEOS3 lg.jpg 3.67 m (144 in) Single United States Air Force Maui Optical Station, Hawaii, USA 1996
3.6 m Devasthal Optical Telescope[12] (DOT) 3.6m Devasthal Optical Telescope.jpg 3.6 m (142 in) Single India ARIES Devasthal Observatory, Nainital, India 2016
Telescopio Nazionale Galileo (TNG) Tng 2001.jpg 3.58 m (141 in) Single Italy Roque de los Muchachos Obs., Canary Islands, Spain 1997
New Technology Telescope (NTT) La Silla NTT.jpg 3.58 m (141 in) Single ESO countries La Silla Observatory, Coquimbo Region, Chile 1989
Canada-France-Hawaii Telescope (CFHT) Canada-France-Hawaii-Telescope-dome.jpeg 3.58 m (141 in) Single Canada , France , United States Mauna Kea Observatories, Hawaii, USA 1979
ESO 3.6 m Telescope Wallpaper of 3.6-m Telescope at La Silla.jpg 3.57 m (141 in) Single ESO countries La Silla Observatory, Coquimbo Region, Chile 1977
MPI-CAHA 3.5 m[13] Bacares09.jpg 3.5 m (138 in) Single West Germany, Spain Calar Alto Obs., Almería, Spain 1984
USAF Starfire 3.5 m[14] Big3 5mtele.png 3.5 m (138 in) Single United States Starfire Optical Range, New Mexico, USA 1994
WIYN Telescope WIYN OBSERVATORY ON KITT PEAK.jpg 3.5 m (138 in) Single United States Kitt Peak National Obs., Arizona, USA 1994
Space Surveillance Telescope Space Surveillance Telescope.jpg 3.5 m (138 in) Single United States , Australia White Sands Missile Range, New Mexico, United States
Relocated to
Harold E. Holt Naval Communication Station, Western Australia.
2011
Relocated
2020
Astrophysical Research Consortium (ARC) D70050914 15 ApolloLLR.jpg 3.48 m (137 in) Single United States Apache Point Obs., New Mexico, USA 1994
Iranian National Observatory (INO340)
INO340.png
3.4 m (130 in) Single Iran Mount Gargash, Isfahan Province, Iran 2022[15]
Shane Telescope Shane dome.JPG 3.05 m (120 in) Single United States Lick Observatory, California , USA 1959
NASA Infrared Telescope Facility Afshin Darian - NASA Infrared Telescope Facility.jpg 3.0 m (118 in) Single United States Mauna Kea Observatory, Hawaii, USA 1979
NASA-LMT Liquid Mirror Telescope.jpg 3 m (118 in) Liquid United States NASA Orbital Debris Obs., New Mexico, USA 1995
Decommissioned 2002[16]
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.[17] The Steward Observatory Mirror Lab cast and polished the two LBT mirrors, the two Magellan mirrors, the MMT replacement mirror, and the LSST primary/tertiary mirror. It is currently making the mirrors for the Giant Magellan Telescope.[18] The Keck segments were made by Schott AG. The SALT and LAMOST segments were cast and polished by LZOS.[19] The mirror for Subaru was cast by Corning and polished at Contraves Brashear Systems in Pennsylvania, USA.[20]

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 telescopes

These telescopes were the largest in the world at the time of their construction, by the same aperture criterion as above.

Reflecting telescopes (chronologically)
Years Largest Name Out In Aperture (m) Area (m2) M1 Mirror Note Altitude (m)
2009–Present Gran Telescopio Canarias Grantelescopio.jpg Gran Telescopio Canarias.jpg 10.4 74 36 × 1.9 m hexagons M1 mirror Segmented mirror 2267
1993–2009 Keck 1 KeckTwilight-hi.png KeckObservatory20071013.jpg 10 76 [21] 36 × 1.8 m hexagons M1 mirror Segmented mirror, M1 f/1.75 4145
1976–1993 BTA-6 Главная обсерватория.jpg SAO-6m-Telescope-main-mirror.jpg 6 26 605 cm f/4 M1 mirror Mirror replaced twice 2070
1948–1976 Hale (200 inch) P200 Dome Open.jpg Palomar arp 600pix.jpg 5.1 508 cm f/3.3 M1 mirror Art deco dome 1713
1917–1948 Hooker (100 inch) 100inchHooker.jpg 2.54 Also used for 1st optical interferometer 1742
For earlier entries, see List of largest optical telescopes historically

Future telescopes

Under construction

The Extremely Large Telescope under construction, 2 August 2023

These telescopes are under construction and will meet the list inclusion criteria once completed:

  • Extremely Large Telescope, Chile – 39.3 m (1,550 in). Construction began in 2018, first light planned in 2028.[22]
  • Thirty Meter Telescope, Hawaii, USA – 30 m (1,200 in). Construction began in 2014 but halted in 2015; (As of 2022) it has not resumed.[23]
  • Giant Magellan Telescope, Chile – seven 8.4 m mirrors on a single mount. This provides an effective aperture equivalent to a 21.4 m mirror and the resolving power equivalent to a 24.5 m mirror. First light planned in 2029.[24]
  • Vera C. Rubin Observatory, Chile – 8.4 m (330 in). First light planned in 2024.[25]
  • San Pedro Martir Telescope, Baja California, Mexico – 6.5 m (260 in). First light planned in 2023.[26]
  • Tokyo Atacama Observatory (TAO) – 6.5 m (260 in). First light planned for 2023.[27]
  • Magdalena Ridge Observatory Interferometer, New Mexico, USA – An optical interferometer array with ten 1.4 m (55 in) telescopes. The light gathering power is equivalent to a 4.4 m (170 in) single aperture. The first telescope was installed in 2016; construction was paused in 2019 due to insufficient funding[28] and has not resumed.
  • Timau National Observatory, Indonesia – 3.8 m (150 in). Construction expected to be completed in 2023.[29]

Proposed

A comparison between the primary mirrors of the Hubble Space Telescope, James Webb Space Telescope, LUVOIR-B and LUVOIR-A
Scale comparison between the primary mirrors of the Hubble Space Telescope, James Webb Space Telescope, and the proposed LUVOIR-B and LUVOIR-A.

Selected large telescopes which are in detailed design or pre-construction phases:

See also

References

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  2. 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
  3. "Upgraded Hobby–Eberly Telescope Sees First Light". https://mcdonaldobservatory.org/news/releases/20151102. 
  4. "Howstuffworks "10 Amazing Telescopes"". Science.howstuffworks.com. http://science.howstuffworks.com/ten-amazing-telescopes.htm/printable. 
  5. "The Carnegie Observatories – Magellan Telescopes". Carnegie Institution for Science. http://obs.carnegiescience.edu/Magellan. 
  6. Andersen, Geoff. The Telescope, p. 165
  7. [1]
  8. "LAMOST Homepage – Gallery". Lamost.org. August 13, 2012. http://www.lamost.org/public/gallery. 
  9. Dwayne DayMonday, May 11, 2009 (2009-05-11). "Mirrors in the dark". The Space Review. http://www.thespacereview.com/article/1371/1. 
  10. Lowell Observatory – 4.3-meter DCT
  11. "The Mayall 4-Meter Telescope". Noao.edu. February 27, 1973. http://www.noao.edu/outreach/kptour/mayall.html. 
  12. Sagar, Ram; Kumar, Brijesh; Omar, Amitesh; Pandey, A. K. (2012). "New optical telescope projects at Devasthal Observatory". Proceedings of the Society of Photo-Optical Instrumentation Engineers. Ground-based and Airborne Telescopes IV 8444: 84441T. doi:10.1117/12.925634. Bibcode2012SPIE.8444E..1TS. 
  13. "Max-Planck-Institut für Astronomie". Mpia.de. July 20, 1994. http://www.mpia.de/Public/menu_q2.php?Aktuelles/PR/2004/PR041116/PR_041116_en.html. 
  14. Pike, John. "Starfire". Globalsecurity.org. http://www.globalsecurity.org/space/systems/starfire.htm. 
  15. Stone, Richard (19 October 2022). "'The door is open': Iranian astronomers seek collaborations for their new, world-class telescope". Science. doi:10.1126/science.adf4145. https://www.science.org/content/article/door-open-iranian-astronomers-seek-collaborations-their-new-world-class-telescope. 
  16. "NASA Orbital Debris Observatory". Astro.ubc.ca. http://www.astro.ubc.ca/lmt/Nodo/index.html. 
  17. "Polissage Optique pour les Grands Instruments de la Physique et de l 'Astronomie". http://www.rdv-routedeslasers.com/polissage/tele/interventions/8_E_Ruch_SAGEM_REOSC.pdf. 
  18. "Mirror Castings". Steward Observatory Mirror Lab. https://mirrorlab.arizona.edu/content/mirror-castings. 
  19. "Large Optics Manufacturing in Large Optics Manufacturing in Lytkarino Optical Glass Factory, Russia". http://www.opticinnovations.co.uk/attachments/article_with_pdf_attachments/Large%20size%20and%20high%20aperture%20%20optics%20produced%20by%20LZOS%20.pdf. 
  20. "SUBARU Telescope 8.3m Primary Mirror Finished". http://carlkop.home.xs4all.nl/subaru.html. 
  21. "Keck Telescope Facts". Spacecraftkits.com. http://spacecraftkits.com/KFacts.html. 
  22. "Timeline". European Southern Observatory. https://elt.eso.org/about/timeline/. 
  23. "Timeline". TMT International Observatory. https://www.tmt.org/page/timeline. 
  24. "Quick Facts". Gmto.org. https://www.gmto.org/overview/quick-facts/. 
  25. "Construction Project Status". Rubin Observatory. 16 October 2022. https://www.lsst.org/about/project-status. "14-Mar-2024 System First Light" 
  26. Universities in U.S. and Mexico Partner on Telescope Project. Arizona Public Media, 13 November 2017.
  27. Yoshii, Y.; Doi, M.; Kohno, K.; Miyata, T.; Motohara, K.; Kawara, K.; Tanaka, M.; Minezaki, T. et al. (2016). "The University of Tokyo Atacama Observatory 6.5m telescope: Project overview and current status". Ground-Based and Airborne Telescopes VI 9906: 99060R. doi:10.1117/12.2231391. Bibcode2016SPIE.9906E..0RY. 
  28. Creech-Eakman, Michelle J.; Romero, V. D.; Haniff, Christopher A.; Buscher, David F.; Young, J. S.; Olivares, Andres; Ligon, E. R.; Payne, I. et al. (13 December 2020). "Setting the stage for first fringes with the Magdalena Ridge Observatory Interferometer". Optical and Infrared Interferometry and Imaging VII. 11446. p. 1144609. doi:10.1117/12.2563173. Bibcode2020SPIE11446E..09C. https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11446/2563173/Setting-the-stage-for-first-fringes-with-the-Magdalena-Ridge/10.1117/12.2563173.short. 
  29. "Pembangunan Observatorium Nasional Timau segera Rampung" (in id-ID). 2023-07-30. https://www.brin.go.id/news/113812/pembangunan-observatorium-nasional-timau-segera-rampung. 
  30. Zhang, Yifan; Jiang, Haijiao; Shectman, Stephen; Yang, Dehua; Cai, Zheng; Shi, Yong; Huang, Song; Lu, Lu et al. (2023). "Conceptual design of the optical system of the 6.5m wide field multiplexed survey telescope with excellent image quality". PhotoniX 4 (4): 16. doi:10.1186/s43074-023-00094-4. https://www.researchsquare.com/article/rs-2136738/latest.pdf. 
  31. "Introduction to the Chinese Giant Solar Telescope". http://www.ncra.tifr.res.in:8081/~basi/ASICS_2/031-Deng.pdf. 
  32. Staff (29 August 2012). "China Exclusive: Scientists looking for site for giant solar telescope". http://www.spacedaily.com/reports/China_Exclusive_Scientists_looking_for_site_for_giant_solar_telescope_999.html. 
  33. Shiga, David (2 June 2008). "Liquid-mirror telescopes are a reality at last". New Scientist. https://www.newscientist.com/article/dn14030-liquid-mirror-telescopes-are-a-reality-at-last/. 
  34. "Advanced Liquid-mirror Probe of Astrophysics, Cosmology and Asteroids)". Astronomy and Astrophysics at the University of British Columbia. https://www.astro.ubc.ca/LMT/alpaca/index.html. 

Further reading

External links