View source for List of largest optical reflecting telescopes

{{Short description|none}}
{{Multiple image
| perrow            = 3
| total_width       = 400
| image1            = Grantelescopio.jpg
| image2            = KeckTelescopes-hi.png
| image3            = MaunaKea Subaru.jpg
| image4            = HET Dome.jpg
| image5            = LargeBinoTelescope NASA.jpg
| image6            = Paranal opendome.jpg
| image7            = Southern African Large Telescope 720x576px.jpg
| image8            = Panorama of Rubin During First Look Observations (500 megapixels) (noirlab2521w).jpg
| image9            = Gemini South 01.jpg
| caption1          = [[Gran Telescopio Canarias]]
| caption2          = [[W. M. Keck Observatory]]
| caption3          = [[Subaru Telescope]]
| caption4          = [[Hobby–Eberly Telescope]]
| caption5          = [[Large Binocular Telescope]]
| caption6          = [[Very Large Telescope]]
| caption7          = [[Southern African Large Telescope]]
| caption8          = [[Vera C. Rubin Observatory|Simonyi Survey Telescope]]
| caption9          = [[Gemini Observatory]]
| header            = Telescopes with aperture diameter >8 metres
}}

This '''list of the largest optical reflecting telescopes''' with [[Objective (optics)|objective]] diameters of {{Convert|3.0|m|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 interferometer]]s such as the Keck I and II used together as the [[Keck Interferometer]] (up to 85&nbsp;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&nbsp;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 observatory|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.<ref>{{Cite web|last=|title=Neptune from the VLT and Hubble|url=https://www.eso.org/public/images/eso1824c/|access-date=2021-02-23|website=www.eso.org|language=en}}</ref> Another advantage of Earth based telescopes is the comparatively low cost of upgrading and replacing instruments.
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==Table of reflecting telescopes==
Telescopes in this list are ordered by effective optical [[aperture]], given as the diameter of a circle with equivalent collecting area. Aperture has historically been a useful gauge of telescopes' limiting resolution, optical area, physical size, and cost. Multiple mirror or [[segmented mirror]] telescopes that are on the same mount and usually form a single combined image are ranked by their equivalent combined aperture. Telescopes that cannot use their entire primary mirror at once (e.g. HET or LAMOST) are listed by their maximum effective aperture. Telescopes that are sometimes used for [[astronomical optical interferometry|optical interferometry]] are listed individually, not as a combined instrument. All telescopes with an effective aperture of at least {{convert|3.00|m|in}} at [[visible light|visible]] or [[near-infrared]] wavelengths are included; selected smaller telescopes [[List of large optical telescopes|are listed elsewhere]].

{| class="wikitable sortable" style="margin: 1em auto 1em auto; width:90%; font-size:95%;"
|+Reflecting telescopes
|-
! Name || class="unsortable"| Image ||data-sort-type="number"| Effective [[aperture]] || [[Telescope|Mirror type]] || Nationality / Sponsors || Site || [[First light (astronomy)|First light]] 
|-
| [[Large Binocular Telescope]] (LBT) || [[File:LargeBinoTelescope NASA½.jpg|50px]] || {{convert|11.9|m|in|sigfig=3|abbr=on}} (combined)<ref>[http://oldweb.lbto.org/pdfs/06_Orlando.pdf 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]</ref>||Multiple<br/><small>Two {{convert|8.4|m|in|sigfig=3|abbr=on}} mirrors</small>|| [[United States|USA]], Italy, Germany || [[Mount Graham International Observatory]], [[Arizona]], USA || 2005 
|-
| [[Gran Telescopio Canarias]] (GTC) || [[File:Grantelescopio.jpg|50px]] || {{convert|10.4|m|in|sigfig=3|abbr=on}} || Segmented<br/><small>36 hexagonal segments</small> || [[Spain]], [[Mexico]], [[United States|USA]] || [[Roque de los Muchachos Observatory|Roque de los Muchachos Obs.]], [[Canary Islands]], Spain || 2006
|-
| [[Hobby–Eberly Telescope]] (HET) || [[File:HET Dome.jpg|50px]] || {{convert|10|m|in|sigfig=3|abbr=on}} (effective) <ref>{{Cite web|url=https://mcdonaldobservatory.org/news/releases/20151102|title=Upgraded Hobby–Eberly Telescope Sees First Light|website=McDonald Observatory|access-date=2016-07-29}}</ref> || Segmented<br/><small>91 × {{convert|1|m|in|sigfig=2|abbr=on}} hexagonal segments forming an 11&nbsp;m × 9.8&nbsp;m mirror</small> || [[United States|USA]], Germany || [[McDonald Observatory]], [[Texas]], USA || 1997<br/><small>Aperture increased 2015</small>
|- 
| [[Keck telescope|Keck]] 1 || [[File:KeckTelescopes-hi.png|50px]] || {{convert|10|m|in|sigfig=3|abbr=on}} || Segmented<br/><small>36 hexagonal segments</small> || [[United States|USA]] || [[Mauna Kea Observatories]], [[Hawaii]], USA || 1993
|-
| [[Keck telescope|Keck]] 2 || [[File:KeckTelescopes-hi.png|50px]] || {{convert|10|m|in|sigfig=3|abbr=on}} || Segmented<br/><small>36 hexagonal segments</small> || [[United States|USA]] || [[Mauna Kea Observatories]], [[Hawaii]], USA || 1996
|- 
| [[Southern African Large Telescope]] (SALT) || [[File:Southern African Large Telescope 720x576px.jpg|50px]] || {{convert|9.2|m|in|sigfig=3|abbr=on}} (effective)<ref>{{cite web|url=http://science.howstuffworks.com/ten-amazing-telescopes.htm/printable |title=Howstuffworks "10 Amazing Telescopes" |publisher=Science.howstuffworks.com |access-date=August 19, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20081222135123/http://science.howstuffworks.com/ten-amazing-telescopes.htm/printable |archive-date=December 22, 2008 }}</ref> || Segmented<br/><small>91 × {{convert|1|m|in|sigfig=2|abbr=on}} hexagonal segments forming an 11&nbsp;m × 9.8&nbsp;m mirror</small> || [[South Africa]], [[United States|USA]], [[United Kingdom|UK]], Germany, [[Poland]], New Zealand || [[South African Astronomical Observatory|South African Astronomical Obs.]], [[Northern Cape]], South Africa || 2005
|-
| [[Vera C. Rubin Observatory|Simonyi Survey Telescope]] (SST) || [[File:Panorama of Rubin During First Look Observations (500 megapixels) (noirlab2521w).jpg|50px]] || {{convert|8.4|m|in|sigfig=3|abbr=on}} || Single || [[United States|USA]] || [[Vera C. Rubin Observatory]], [[Coquimbo Region]], Chile || 2025 
|-
| [[Subaru (telescope)|Subaru]] (JNLT) || [[File:MaunaKea Subaru.jpg|50px]] || {{convert|8.2|m|in|sigfig=3|abbr=on}} || Single || Japan || [[Mauna Kea Observatories]], [[Hawaii]], USA || 1999 
|-
| [[Very Large Telescope|VLT]] UT1 – Antu || [[File:Paranal opendome.jpg|50px]] || {{convert|8.2|m|in|sigfig=3|abbr=on}} || Single || [[European Southern Observatory|ESO Countries]], [[Chile]] || [[Paranal Observatory]], [[Antofagasta Region]], Chile || 1998
|-
| [[Very Large Telescope|VLT]] UT2 – Kueyen || [[File:UVES on UT2-KUEYEN.jpg|50px]] || {{convert|8.2|m|in|sigfig=3|abbr=on}} || Single || [[European Southern Observatory|ESO Countries]], [[Chile]] || [[Paranal Observatory]], [[Antofagasta Region]], Chile || 1999
|-
| [[Very Large Telescope|VLT]] UT3 – Melipal || [[File:Paranal UT3 2008-01-04.jpg|50px]] || {{convert|8.2|m|in|sigfig=3|abbr=on}}  || Single || [[European Southern Observatory|ESO Countries]], [[Chile]] || [[Paranal Observatory]], [[Antofagasta Region]], Chile || 2000
|-
| [[Very Large Telescope|VLT]] UT4 – Yepun || [[File:Cloaked in Stars.jpg|50px]] || {{convert|8.2|m|in|sigfig=3|abbr=on}}  || Single || [[European Southern Observatory|ESO Countries]], [[Chile]] || [[Paranal Observatory]], [[Antofagasta Region]], Chile || 2001
|-
| [[Gemini telescope|Gemini]] North {{small|(Gillett)}} || [[File:Gemini Observatory at sunset.jpg|50px]] || {{convert|8.1|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]], [[United Kingdom|UK]], Canada, [[Chile]], Australia, [[Argentina]], [[Brazil]] || [[Mauna Kea Observatories]], [[Hawaii]], USA || 1999
|-
| [[Gemini telescope|Gemini]] South || [[File:Gemini South 01.jpg|50px]] || {{convert|8.1|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]], [[United Kingdom|UK]], Canada, [[Chile]], Australia, [[Argentina]], [[Brazil]] || [[Cerro Pachón]] (CTIO), [[Coquimbo Region]], Chile || 2001 
|-
| [[James Webb Space Telescope]]
| [[File:JWST spacecraft model 3.png|50px]]
| 6.5 m
(256 in)
| Segmented<br/><small>18 hexagonal segments</small>
| [[NASA]], [[ESA]], [[Canadian Space Agency|CSA]]
| [[Halo orbit]] around the [[Lagrange point#Sun-Earth|Earth-Sun L2 Point]]
| 2022
|-
| [[MMT Observatory|MMT]] (current optics) || [[File:MMT Observatory.jpg|50px]] || {{convert|6.5|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Fred Lawrence Whipple Observatory|F. L. Whipple Obs.]], [[Arizona]], USA || 2000
|-
| [[Magellan (Telescopes)|Magellan]] 1 {{small|(Walter Baade)}}<ref>{{cite web |url=http://obs.carnegiescience.edu/Magellan |title=The Carnegie Observatories – Magellan Telescopes |publisher=[[Carnegie Institution for Science]] |access-date=2017-05-24 |archive-date=2017-05-25 |archive-url=https://web.archive.org/web/20170525193610/http://obs.carnegiescience.edu/magellan |url-status=dead }}</ref> || [[File:Magellan telescopes.jpg|50px]] || {{convert|6.5|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Las Campanas Observatory|Las Campanas Obs.]], [[Atacama Region]], Chile || 2000 
|-
| [[Magellan (Telescopes)|Magellan]] 2 {{small|(Landon Clay)}} || [[File:Magellan telescopes.jpg|50px]] ||{{convert|6.5|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Las Campanas Observatory|Las Campanas Obs.]], [[Atacama Region]], Chile || 2002 
|-
|[[University of Tokyo Atacama Observatory|Tokyo Atacama Observatory]] (TAO)
|
|{{convert|6.5|m|in|sigfig=3|abbr=on}}
|Single
|[[Japan]]
|[[Purico Complex|Cerro Chajnantor]], [[Atacama Desert]], [[Chile]]
|2024<ref>{{Cite web |last=Carter |first=Jamie |title=Meet The Highest Telescope In The World, Which Just Looked Up For The First Time |url=https://www.forbes.com/sites/jamiecartereurope/2024/05/03/meet-tao-the-highest-telescope-in-the-world-which-just-looked-up-for-the-first-time/ |access-date=2024-05-05 |website=Forbes |language=en}}</ref>
|-
| [[BTA-6]] || | [[File:Главная обсерватория.jpg|50px]] ||{{convert|6|m|in|sigfig=3|abbr=on}} || Single || [[USSR]]/Russia || [[Special Astrophysical Observatory of the Russian Academy of Science|Special Astrophysical Obs.]], [[Karachay–Cherkessia]], Russia || 1975 
|-
| [[Large Zenith Telescope]] (LZT) || [[File:180724main 6-mMirror.jpg|50px]] ||{{convert|6|m|in|sigfig=3|abbr=on}} || [[Liquid-mirror telescope|Liquid]] || [[Canada]], [[France]], United States <ref>Andersen, Geoff. ''The Telescope'', p. 165</ref>|| [[Maple Ridge, British Columbia|Maple Ridge]], [[British Columbia]], Canada || 2003<br/><small>Decommissioned 2016</small>
|-
| [[Hale Telescope]] || [[File:P200 Dome Open.jpg|50px]] || {{convert|200|in|m|sigfig=3|abbr=on|order=flip}}  || Single || [[United States|USA]] || [[Palomar Observatory]], [[California]], USA || 1949
|-
| [[LAMOST]] || [[File:LAMOST telescope org.jpg|50px]] || {{convert|4.9|m|in|sigfig=3|abbr=on}} (effective)<ref>{{cite web|url=http://www.lamost.org/lamost/documents/lamost_review_0810.pdf |archive-url=https://web.archive.org/web/20110722011303/http://www.lamost.org/lamost/documents/lamost_review_0810.pdf|archive-date=July 22, 2011 |title=Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST |quote=the effective aperture in diameter is 3.6m - 4.9m}}</ref>|| Segmented<br/><small>37 segments for the 6.67&nbsp;m × 6.05&nbsp;m primary and 24 segments for the 5.72&nbsp;m × 4.40&nbsp;m corrector; effective aperture 3.6–4.9 m</small><ref>{{cite web |url=http://www.lamost.org/public/gallery |title=LAMOST Homepage – Gallery |publisher=Lamost.org |date=August 13, 2012 |access-date=January 6, 2018}}</ref> || [[China]] || Beijing Astronomical Obs., [[Xinglong Station (NAOC)|Xinglong]], China || 2008 
|-
| [[MMT Observatory|MMT]] (original optics)<br/>{{small|(see above for current version)}} || [[File:MMT Observatory.jpg|50px]]|| {{convert|4.7|m|in|sigfig=3|abbr=on}} (combined)<ref>{{cite web|author=Dwayne DayMonday, May 11, 2009 |url=http://www.thespacereview.com/article/1371/1 |title=Mirrors in the dark |publisher=The Space Review |date=2009-05-11 |access-date=2012-01-03}}</ref> || Multiple<br/><small>Six {{convert|1.8|m|in|sigfig=2|abbr=on}} mirrors</small> || [[United States|USA]] || [[Fred Lawrence Whipple Observatory|F. L. Whipple Obs.]], [[Arizona]], USA || 1979<br/><small>Mirrors removed 1998</small>
|-
| [[Lowell Discovery Telescope]]<ref name="status">{{Cite web |url=https://lowell.edu/research/research-facilities/4-3-meter-dct/ |title=Lowell Observatory – 4.3-meter DCT |access-date=2018-01-06 |archive-date=2016-11-04 |archive-url=https://web.archive.org/web/20161104104938/https://lowell.edu/research/research-facilities/4-3-meter-dct/ |url-status=dead }}</ref>|| [[File:The Dome of Discovery Channel Telecope.JPG|50px]] || {{convert|4.3|m|in|sigfig=3|abbr=on}}  || Single || USA || [[Lowell Observatory]], Happy Jack, Arizona, USA || 2012
|-
| [[William Herschel Telescope]] || [[File:William herschel Telescope Dome.jpg|50px]] || {{convert|4.2|m|in|sigfig=3|abbr=on}}  || Single || [[United Kingdom|UK]], [[Netherlands]], Spain || [[Roque de los Muchachos Observatory|Roque de los Muchachos Obs.]], [[Canary Islands]], Spain || 1987 
|-
| [[SOAR telescope|SOAR]] || [[File:SOAR telescope at twlight.jpg|50px]] || {{convert|4.1|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]], [[Brazil]] || [[Cerro Pachón]] (CTIO), [[Coquimbo Region]], Chile || 2002
|-
| [[VISTA (telescope)|VISTA]] || [[File:VISTA at Paranal Eso0704b.tif|50px]] || {{convert|4.1|m|in|sigfig=3|abbr=on}}  || Single || [[European Southern Observatory|ESO Countries]], [[Chile]] || [[Paranal Observatory]], [[Antofagasta Region]], Chile || 2009
|-
| [[Víctor M. Blanco Telescope]] || [[File:4m-Victor M. Blanco Telescope.jpg|50px]] || {{convert|4|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Cerro Tololo Inter-American Observatory|Cerro Tololo Inter-American Obs.]], [[Coquimbo Region]], Chile || 1976
|-
| [[International Liquid Mirror Telescope]] || <!-- [[File:_______.jpg|50px]] --> || {{convert|4|m|in|sigfig=3|abbr=on}}  || [[Liquid-mirror telescope|Liquid]] || [[Belgium]], [[Canada]], [[India]], [[Poland]] || [[Aryabhatta Research Institute of Observational Sciences|ARIES]] Devasthal Observatory, [[Nainital]], India|| 2022
|-
| [[Nicholas U. Mayall Telescope|Nicholas U. Mayall 4 m]]<ref>{{cite web|url=http://www.noao.edu/outreach/kptour/mayall.html |title=The Mayall 4-Meter Telescope |publisher=Noao.edu |date=February 27, 1973 |access-date=August 19, 2009}}</ref> || [[File:Kittpeakteliscope.JPG|50px]] || {{convert|4|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Kitt Peak National Observatory|Kitt Peak National Obs.]], [[Arizona]], USA || 1973
|-
| [[Daniel K. Inouye Solar Telescope]] || [[File:Haleakala Observatory 2017.jpg|50px]] || {{convert|4|m|in|sigfig=3|abbr=on}} || Single || [[United States|USA]] || [[Haleakala Observatory]], [[Hawaii]], USA || 2019
|-
| [[Anglo-Australian Telescope]] (AAT) || [[File:Anglo-Australian Telescope dome.JPG|50px]] || {{convert|3.89|m|in|sigfig=3|abbr=on}}  || Single || Australia, [[United Kingdom|UK]] || [[Australian Astronomical Observatory|Australian Astronomical Obs.]], [[New South Wales]], Australia || 1974
|-
| [[United Kingdom Infrared Telescope]] (UKIRT) || [[File:UKIRT at sunset (straightened).jpg|50px]] || {{convert|3.8|m|in|sigfig=2|abbr=on}}  || Single || [[United Kingdom|UK]], [[United States]] || [[Mauna Kea Observatories]], [[Hawaii]], USA || 1979
|-
| [[3.67 m Advanced Electro Optical System Telescope|3.67 m AEOS Telescope]] (AEOS) || [[File:AEOS3 lg.jpg|50px]] || {{convert|3.67|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Air Force Maui Optical Station]], [[Hawaii]], USA || 1996
|-
| [[3.6 m Devasthal Optical Telescope]]<ref>{{cite book |last1=Sagar |first1=Ram |last2=Kumar |first2=Brijesh |last3=Omar |first3=Amitesh |last4=Pandey |first4=A. K. |chapter=New optical telescope projects at Devasthal Observatory |date=2012 |title=Ground-based and Airborne Telescopes IV |series=Proceedings of the SPIE |volume=8444 |pages=84441T |arxiv=1304.2474 |bibcode=2012SPIE.8444E..1TS |doi=10.1117/12.925634 |s2cid=119272065 |editor-first1=Larry M. |editor-first2=Roberto |editor-first3=Helen J. |editor-last1=Stepp |editor-last2=Gilmozzi |editor-last3=Hall}}</ref> (DOT) || [[File:3.6m Devasthal Optical Telescope.jpg|50px]]|| {{convert|3.6|m|in|sigfig=3|abbr=on}}  || Single || India || [[Aryabhatta Research Institute of Observational Sciences|ARIES]] Devasthal Observatory, [[Nainital]], India|| 2016
|-
| [[Telescopio Nazionale Galileo]] (TNG) || [[File:Tng 2001.jpg|50px]] || {{convert|3.58|m|in|sigfig=3|abbr=on}}  || Single || Italy || [[Roque de los Muchachos Observatory|Roque de los Muchachos Obs.]], [[Canary Islands]], Spain || 1997
|-
| [[New Technology Telescope]] (NTT) || [[File:La Silla NTT.jpg|50px]] || {{convert|3.58|m|in|sigfig=3|abbr=on}}  || Single || [[European Southern Observatory|ESO countries]] || [[La Silla Observatory]], [[Coquimbo Region]], Chile || 1989
|-
| [[Canada-France-Hawaii Telescope]] (CFHT) || [[File:Canada-France-Hawaii-Telescope-dome.jpeg|50px]] || {{convert|3.58|m|in|sigfig=3|abbr=on}}  || Single || [[Canada]], [[France]], [[United States|USA]] || [[Mauna Kea Observatories]], [[Hawaii]], USA || 1979
|-
| [[ESO 3.6 m Telescope]] || | [[File:Wallpaper of 3.6-m Telescope at La Silla.jpg|50px]] || {{convert|3.57|m|in|sigfig=3|abbr=on}}  || Single || [[European Southern Observatory|ESO countries]] || [[La Silla Observatory]], [[Coquimbo Region]], Chile || 1977
|-
| [[Max Planck Institute for Astronomy|MPI]]-[[Calar Alto Observatory|CAHA]] 3.5&nbsp;m<ref name="autogenerated2004">{{cite web|url=http://www.mpia.de/Public/menu_q2.php?Aktuelles/PR/2004/PR041116/PR_041116_en.html |title=Max-Planck-Institut für Astronomie |publisher=Mpia.de |date=July 20, 1994 |access-date=August 19, 2009}}</ref> || [[File:Bacares09.jpg|50px]] || {{convert|3.5|m|in|sigfig=3|abbr=on}} || Single || [[West Germany]], Spain || [[Calar Alto Observatory|Calar Alto Obs.]], [[Almería]], Spain || 1984
|-
| [[Starfire Optical Range|USAF Starfire 3.5 m]]<ref>{{cite web |author=Pike |first=John |title=Starfire |url=http://www.globalsecurity.org/space/systems/starfire.htm |access-date=August 19, 2009 |publisher=Globalsecurity.org}}</ref>|| | [[File:Big3 5mtele.png|50px]] || {{convert|3.5|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Starfire Optical Range]], [[New Mexico]], USA || 1994
|-
| [[WIYN Observatory|WIYN Telescope]] || [[File:WIYN OBSERVATORY ON KITT PEAK.jpg|50px]] || {{convert|3.5|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Kitt Peak National Observatory|Kitt Peak National Obs.]], [[Arizona]], USA || 1994
|-
| [[Space Surveillance Telescope]] || [[File:Space Surveillance Telescope.jpg|50px]] || {{convert|3.5|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]], [[Australia]]|| [[White Sands Missile Range]], New Mexico, United States<br/><small>Relocated to</small><br/>[[Naval Communication Station Harold E. Holt|Harold E. Holt Naval Communication Station]], [[Western Australia]]. || 2011<br/><small>Relocated</small><br/>2020
|-
| [[Astrophysical Research Consortium]] (ARC) || [[File:D70050914 15 ApolloLLR.jpg|50px]] || {{convert|3.48|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Apache Point Observatory|Apache Point Obs.]], [[New Mexico]], USA || 1994
|-
|[[Iranian National Observatory]] (INO340) ||[[File:INO340.png|left|61x61px]]||{{convert|3.4|m|in|sigfig=2|abbr=on}}||Single||[[Iran]]||[[Mount Gargash]], [[Isfahan Province]], Iran ||2022<ref>{{cite news |last1=Stone |first1=Richard |title='The door is open': Iranian astronomers seek collaborations for their new, world-class telescope |url=https://www.science.org/content/article/door-open-iranian-astronomers-seek-collaborations-their-new-world-class-telescope |access-date=21 October 2022 |work=[[Science (journal)|Science]] |date=19 October 2022 |doi=10.1126/science.adf4145}}</ref>
|-
| [[C. Donald Shane telescope|Shane Telescope]] || [[File:Shane dome.JPG|50px]] || {{convert|3.05|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Lick Observatory]], [[California]], USA || 1959
|- 
| [[NASA Infrared Telescope Facility]] || [[File:Afshin Darian - NASA Infrared Telescope Facility.jpg|50px]] || {{convert|3.0|m|in|sigfig=3|abbr=on}}  || Single || [[United States|USA]] || [[Mauna Kea Observatory]], [[Hawaii]], USA || 1979
|- 
| [[NASA-LMT]] || [[File:Liquid Mirror Telescope.jpg|50px]] || {{convert|3|m|in|sigfig=3|abbr=on}} || [[Liquid-mirror telescope|Liquid]]|| [[United States|USA]] || [[NASA Orbital Debris Observatory|NASA Orbital Debris Obs.]], [[New Mexico]], USA || 1995<br/><small>Decommissioned 2002</small><ref>{{cite web|url=http://www.astro.ubc.ca/lmt/Nodo/index.html |title=NASA Orbital Debris Observatory |publisher=Astro.ubc.ca |access-date=August 19, 2009}}</ref>
<!-- Do not add any telescopes smaller than 3.0m. See the inclusion criteria stated in the lead section -->
|- class="sortbottom"
|colspan=8 style="padding: 8px; background-color: #f2f2f2; text-align: center;" | ''For continuation of this list, see [[List of large optical reflecting telescopes]]''
|}

{{clear}}

==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.
<!-- sorted by optical aperture, no retrograde--> 
{| class="wikitable sortable" style="margin: 1em auto 1em auto; width:90%; font-size:95%;"
|+Reflecting telescopes (chronologically)
|-
! Years Largest || Name || Out || In || Aperture (m) || Area (m<sup>2</sup>) || M1 Mirror || Note || Altitude (m)
|-
| 2009–Present || [[Gran Telescopio Canarias]] || [[File:Grantelescopio.jpg|50px]] || [[File:Gran Telescopio Canarias.jpg|50px]] || 10.4 || 74 || 36 × 1.9 m hexagons M1 mirror || Segmented mirror || 2267
|-
| 1993–2009 || [[W. M. Keck Observatory|Keck 1]] || [[File:KeckTwilight-hi.png|50px]] || [[File:KeckObservatory20071013.jpg|40px]] || 10 || 76 <ref name="spacecraftkits.com">{{cite web|url=http://spacecraftkits.com/KFacts.html |title=Keck Telescope Facts |publisher=Spacecraftkits.com |access-date=2012-01-03}}</ref> || 36 × 1.8 m hexagons M1 mirror || Segmented mirror, M1 f/1.75 || 4145
|-
| 1976–1993 || [[BTA-6]] || [[File:Главная обсерватория.jpg|50px]] || [[File:SAO-6m-Telescope-main-mirror.jpg|50px]] || 6 || 26 || 605&nbsp;cm f/4 M1 mirror || Mirror replaced twice || 2070
|-
| 1948–1976 || [[Hale Telescope|Hale (200 inch)]] || [[File:P200 Dome Open.jpg|50px]] || [[File:Palomar arp 600pix.jpg|50px]] || 5.1 || &ndash; || 508&nbsp;cm f/3.3 M1 mirror || [[Art deco]] dome || 1713
|-
| 1917–1948 || [[Hooker telescope|Hooker (100 inch)]] || || [[File:100inchHooker.jpg|30px]] || 2.54 || &ndash; || || Also used for 1st optical interferometer || 1742
|- class=sortbottom
|colspan=9|For earlier entries, see [[List of largest optical telescopes historically]]
|}
<!-- next for glass mirrors, A.A. Common Harvard 60 inch and/or the Mt. Wilson Hale 60 inch -->

[[File:Telescopes Size and Year Built.png|thumb|450px|center|Large reflecting telescopes over time. The horizontal axis indicates the year built and the vertical axis is the size of the mirror measured in meters. Selected countries are color-coded (see legend).]]
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==Future telescopes==

===Under construction===
[[File:A towering telescope (DJI 0976).jpg|thumb|upright=1.6|The [[Extremely Large Telescope]] under construction in 1 May 2025]]
These telescopes are under construction and will meet the list inclusion criteria once completed:
<!-- Ordered by effective aperture -->
* [[Extremely Large Telescope]], Chile – {{convert|39.3|m|in|sigfig=3|abbr=on}}. Construction began in 2018, [[First light (astronomy)|first light]] planned in 2028.<ref>{{Cite web |title=Timeline |website=The Extremely Large Telescope |publisher=European Southern Observatory |url=https://elt.eso.org/about/timeline/ |access-date=2023-09-03}}</ref>
* [[Thirty Meter Telescope]], Hawaii, USA – {{convert|30|m|in|sigfig=2|abbr=on}}. Construction began in 2014 but halted in 2015; {{as of|lc=yes|2022}} it has not resumed.<ref>{{cite web |title=Timeline |url=https://www.tmt.org/page/timeline |publisher=TMT International Observatory |access-date=27 September 2022}}</ref>
* [[Giant Magellan Telescope]], Chile – seven 8.4&nbsp;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.<ref>{{cite web|url=https://www.gmto.org/overview/quick-facts/ |title=Quick Facts |publisher=Gmto.org |access-date=2021-02-15}}</ref>
* [[San Pedro Martir Telescope]], Baja California, Mexico – {{convert|6.5|m|in|sigfig=2|abbr=on}}. First light planned in 2023.<ref>[https://news.azpm.org/p/news-topical-sci/2017/11/13/119939-universities-in-us-and-mexico-partner-on-telescope-project/ Universities in U.S. and Mexico Partner on Telescope Project]. Arizona Public Media, 13 November 2017.</ref>{{needs update|date=October 2024}}
* [[Magdalena Ridge Observatory Interferometer]], New Mexico, USA – An optical interferometer array with ten {{convert|1.4|m|in|sigfig=2|abbr=on}} telescopes. The light gathering power is equivalent to a {{convert|4.4|m|in|abbr=on}} single aperture. The first telescope was installed in 2016; construction was paused in 2019 due to insufficient funding<ref>{{cite conference|display-authors=3 |last1=Creech-Eakman |first1=Michelle J. |last2=Romero |first2=V. D. |last3=Haniff |first3=Christopher A. |last4=Buscher |first4=David F. |last5=Young |first5=J. S. |last6=Olivares |first6=Andres |last7=Ligon |first7=E. R. |last8=Payne |first8=I. |last9=Avila |first9=Bastian |last10=Blevins |first10=Sterling |last11=Chowdhury |first11=Naseef |last12=Collins |first12=Robert |last13=Dahl |first13=Chuck |last14=Das Roy |first14=Dipanjan |last15=Dooley |first15=J. |last16=Etscorn |first16=Dylan |last17=Etscorn |first17=Shelbi |last18=Farris |first18=Allen |last19=Fisher |first19=Martin |last20=Garcia |first20=Erica |last21=Gabaldon |first21=Mateo |last22=Gino |first22=Colleen |last23=Halder |first23=Ratna |last24=Hosseini |first24=Omid |last25=Jaynes |first25=Brandon |last26=Jencka |first26=Louis |last27=Johnston |first27=Perry |last28=Jojola |first28=Stephen |last29=Luis |first29=James |last30=Maes |first30=Jennie |last31=Martin |first31=William |last32=Matthews |first32=Tyler |last33=McKeen |first33=Cailyn |last34=Mohammadi |first34=Sina |last35=Mortimer |first35=Dan |last36=Norouzi |first36=Siavash |last37=Ochoa |first37=Danielle |last38=Panta |first38=Bhola |last39=Pino |first39=Juan |last40=Salayandia |first40=Isaac |last41=Salcido |first41=Chris |last42=Sanchez |first42=Amanda |last43=Santoro |first43=Fernando |last44=Seneta |first44=E. Bodie |last45=Sun |first45=X. |last46=Wilson |first46=Donald |last47=Wolfram |first47=Jeanette |title=Setting the stage for first fringes with the Magdalena Ridge Observatory Interferometer |conference=Optical and Infrared Interferometry and Imaging VII |series=[[Proceedings of the SPIE]] |volume=11446 |page=1144609 |date=13 December 2020 |doi=10.1117/12.2563173 |bibcode=2020SPIE11446E..09C |url=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 |conference-url=https://www.spiedigitallibrary.org/conference-proceedings-of-SPIE/11446.toc|url-access=subscription }}</ref> and has not resumed.
* [[Timau National Observatory]], Indonesia – {{convert|3.8|m|in|sigfig=2|abbr=on}}. Construction expected to be completed by early 2025.<ref>{{Cite web|url=https://www.tempo.co/hiburan/observatorium-nasional-timau-di-ntt-segera-beroperasi-begini-potensi-wisatanya-12852|title=Observatorium Nasional Timau di NTT Segera Beroperasi, Begini Potensi Wisatanya|date=2024-09-04|website=tempo.co|language=id-ID|access-date=2025-01-04}}</ref>

===Proposed===
[[File:Comparison of LUVOIR-A and -B primary mirrors with Hubble and JWST.png|thumb|upright=1.6|alt=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 [[Large UV Optical Infrared Surveyor|LUVOIR-B and LUVOIR-A]].]]
Selected large telescopes which are in detailed design or pre-construction phases:
<!-- Please only add projects which are actively being worked on and have been presented to the scientific community; aspirations aren't enough -->
* [[Large UV Optical Infrared Surveyor]] (LUVOIR), a proposed space telescope for launch in the mid 2030s.
* [[MUltiplexed Survey Telescope]] (MUST), a 6.5 m spectroscopic survey telescope.<ref>{{cite journal|title= Conceptual design of the optical system of the 6.5m wide field multiplexed survey telescope with excellent image quality|journal=PhotoniX|year=2023|doi=10.1186/s43074-023-00094-4|number=4|page=16|last1=Zhang|first1=Yifan|last2=Jiang|first2=Haijiao|last3=Shectman|first3=Stephen|last4=Yang|first4=Dehua|last5=Cai|first5=Zheng|last6=Shi|first6=Yong|last7=Huang|first7=Song|last8=Lu|first8=Lu|last9=Zheng|first9=Yamin|last10=Kang|first10=Shaonan|last11=Mao|first11=Shude|last12=Huang|first12=Lei|volume=4 |s2cid=258766165 |doi-access=free |url=https://www.researchsquare.com/article/rs-2136738/latest.pdf}}</ref>
* [[Chinese Giant Solar Telescope]] (CGST), an infrared and optical solar telescope, with light-gathering power equivalent to a 5&nbsp;m diameter aperture.<ref>{{cite web |title=Introduction to the Chinese Giant Solar Telescope |url=http://www.ncra.tifr.res.in:8081/~basi/ASICS_2/031-Deng.pdf <!--Corrected url via http://freepdfs.net/giant-telescope-will-keep-an-eye-on-planets-in-other-solar/95126eb4a1630a8f8bdc1a439886e404/ to http://freepdfs.net/introduction-to-the-chinese-giant-solar-telescope/fda79c3c8e4463f6fb03964eb3a47871/ to source-->}}</ref><ref>{{cite news |title=China Exclusive: Scientists looking for site for giant solar telescope |url=http://www.spacedaily.com/reports/China_Exclusive_Scientists_looking_for_site_for_giant_solar_telescope_999.html |access-date=8 December 2014 |author=Staff |date=29 August 2012 }}</ref>
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==See also==
* [[List of largest infrared telescopes]]
* [[List of telescope types]]
* [[Lists of telescopes]]

==References==
{{reflist|colwidth=30em}}

==Further reading==
*{{cite journal|bibcode=2004PASP..116...77R|title=The Historical Growth of Telescope Aperture|first=René|last=Racine|journal=Publications of the Astronomical Society of the Pacific|volume=116|issue=815|page=77|year=2004|doi=10.1086/380955|doi-access=free}}

==External links==
* [http://abell.as.arizona.edu/~hill/list/bigtel99.htm List of large reflecting telescopes]
* [http://astro.nineplanets.org/bigeyes.html The World's Largest Optical Telescopes]
* [http://stjarnhimlen.se/bigtel/LargestTelescope.html Largest optical telescopes of the world]
* [http://www.noao.edu/education/gsmt/intro Selected largest telescopes]
* [http://articles.adsabs.harvard.edu//full/1884SidM....3..193P/0000193.000.html Sidereal Messenger Large refracting telescopes] (date 1884)

{{Portal bar|Astronomy|Stars|Outer space|Solar System}}
[[Category:Lists by size|Optical telescopes]]
[[Category:Lists of telescopes|Largest optical telescopes]]
[[Category:Lists of technological superlatives|Telescope]]