List of largest optical reflecting telescopes

This list of the largest optical reflecting telescopes with objective diameters of Template:Convert 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Another advantage of Earth based telescopes is the comparatively low cost of upgrading and replacing instruments. Template:TOC left Template:Comparison optical telescope primary mirrors.svg

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 optical interferometry are listed individually, not as a combined instrument. All telescopes with an effective aperture of at least Template:Convert at visible or near-infrared wavelengths are included; selected smaller telescopes are listed elsewhere.

Reflecting telescopes

Name	Image	Effective aperture	Mirror type	Nationality / Sponsors	Site	First light
Large Binocular Telescope (LBT)	File:LargeBinoTelescope NASA½.jpg	Template:Convert (combined)<ref>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 Two Template:Convert mirrors	USA, Italy, Germany	Mount Graham International Observatory, Arizona, USA	2005
Gran Telescopio Canarias (GTC)	File:Grantelescopio.jpg	Template:Convert	Segmented 36 hexagonal segments	Spain, Mexico, USA	Roque de los Muchachos Obs., Canary Islands, Spain	2006
Hobby–Eberly Telescope (HET)	File:HET Dome.jpg	Template:Convert (effective) <ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || Segmented 91 × Template:Convert hexagonal segments forming an 11 m × 9.8 m mirror || USA, Germany || McDonald Observatory, Texas, USA || 1997 Aperture increased 2015
Keck 1	File:KeckTelescopes-hi.png	Template:Convert	Segmented 36 hexagonal segments	USA	Mauna Kea Observatories, Hawaii, USA	1993
Keck 2	File:KeckTelescopes-hi.png	Template:Convert	Segmented 36 hexagonal segments	USA	Mauna Kea Observatories, Hawaii, USA	1996
Southern African Large Telescope (SALT)	File:Southern African Large Telescope 720x576px.jpg	Template:Convert (effective)<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || Segmented 91 × Template:Convert hexagonal segments forming an 11 m × 9.8 m mirror || South Africa, USA, UK, Germany, Poland, New Zealand || South African Astronomical Obs., Northern Cape, South Africa || 2005
Subaru (JNLT)	File:MaunaKea Subaru.jpg	Template:Convert	Single	Japan	Mauna Kea Observatories, Hawaii, USA	1999
VLT UT1 – Antu	File:Paranal opendome.jpg	Template:Convert	Single	ESO Countries, Chile	Paranal Observatory, Antofagasta Region, Chile	1998
VLT UT2 – Kueyen	File:UVES on UT2-KUEYEN.jpg	Template:Convert	Single	ESO Countries, Chile	Paranal Observatory, Antofagasta Region, Chile	1999
VLT UT3 – Melipal	File:Paranal UT3 2008-01-04.jpg	Template:Convert	Single	ESO Countries, Chile	Paranal Observatory, Antofagasta Region, Chile	2000
VLT UT4 – Yepun	File:Cloaked in Stars.jpg	Template:Convert	Single	ESO Countries, Chile	Paranal Observatory, Antofagasta Region, Chile	2001
Gemini North Template:Small	File:Gemini Observatory at sunset.jpg	Template:Convert	Single	USA, UK, Canada, Chile, Australia, Argentina, Brazil	Mauna Kea Observatories, Hawaii, USA	1999
Gemini South	File:Gemini South 01.jpg	Template:Convert	Single	USA, UK, Canada, Chile, Australia, Argentina, Brazil	Cerro Pachón (CTIO), Coquimbo Region, Chile	2001
James Webb Space Telescope	File: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)	File:MMT Observatory.jpg	Template:Convert	Single	USA	F. L. Whipple Obs., Arizona, USA	2000
Magellan 1 Template:Small<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || File:Magellan telescopes.jpg || Template:Convert || Single || USA || Las Campanas Obs., Atacama Region, Chile || 2000
Magellan 2 Template:Small	File:Magellan telescopes.jpg	Template:Convert	Single	USA	Las Campanas Obs., Atacama Region, Chile	2002
Tokyo Atacama Observatory (TAO)		Template:Convert	Single	Japan	Cerro Chajnantor, Atacama Desert, Chile	citation	CitationClass=web }}</ref>
BTA-6	File:Главная обсерватория.jpg	Template:Convert	Single	USSR/Russia	Special Astrophysical Obs., Karachay–Cherkessia, Russia	1975
Large Zenith Telescope (LZT)	File:180724main 6-mMirror.jpg	Template:Convert	Liquid	Canada, France, United States <ref>Andersen, Geoff. The Telescope, p. 165</ref>	Maple Ridge, British Columbia, Canada	2003 Decommissioned 2016
Hale Telescope	File:P200 Dome Open.jpg	Template:Convert	Single	USA	Palomar Observatory, California, USA	1949
LAMOST	File:LAMOST telescope org.jpg	Template:Convert (effective)<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>|| 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<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || China || Beijing Astronomical Obs., Xinglong, China || 2008
MMT (original optics) Template:Small	File:MMT Observatory.jpg	Template:Convert (combined)<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || Multiple Six Template:Convert mirrors || USA || F. L. Whipple Obs., Arizona, USA || 1979 Mirrors removed 1998
Lowell Discovery Telescope<ref name="status">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>|| File:The Dome of Discovery Channel Telecope.JPG || Template:Convert || Single || USA || Lowell Observatory, Happy Jack, Arizona, USA || 2012
William Herschel Telescope	File:William herschel Telescope Dome.jpg	Template:Convert	Single	UK, Netherlands, Spain	Roque de los Muchachos Obs., Canary Islands, Spain	1987
SOAR	File:SOAR telescope at twlight.jpg	Template:Convert	Single	USA, Brazil	Cerro Pachón (CTIO), Coquimbo Region, Chile	2002
VISTA	File:VISTA at Paranal Eso0704b.tif	Template:Convert	Single	ESO Countries, Chile	Paranal Observatory, Antofagasta Region, Chile	2009
Víctor M. Blanco Telescope	File:4m-Victor M. Blanco Telescope.jpg	Template:Convert	Single	USA	Cerro Tololo Inter-American Obs., Coquimbo Region, Chile	1976
International Liquid Mirror Telescope		Template:Convert	Liquid	Belgium, Canada, India, Poland	ARIES Devasthal Observatory, Nainital, India	2022
Nicholas U. Mayall 4 m<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || File:Kittpeakteliscope.JPG || Template:Convert || Single || USA || Kitt Peak National Obs., Arizona, USA || 1973
Daniel K. Inouye Solar Telescope	File:Haleakala Observatory 2017.jpg	Template:Convert	Single	USA	Haleakala Observatory, Hawaii, USA	2019
Anglo-Australian Telescope (AAT)	File:Anglo-Australian Telescope dome.JPG	Template:Convert	Single	Australia, UK	Australian Astronomical Obs., New South Wales, Australia	1974
United Kingdom Infrared Telescope (UKIRT)	File:UKIRT at sunset (straightened).jpg	Template:Convert	Single	UK, United States	Mauna Kea Observatories, Hawaii, USA	1979
3.67 m AEOS Telescope (AEOS)	File:AEOS3 lg.jpg	Template:Convert	Single	USA	Air Force Maui Optical Station, Hawaii, USA	1996
3.6 m Devasthal Optical Telescope<ref>Template:Cite book</ref> (DOT)	File:3.6m Devasthal Optical Telescope.jpg	Template:Convert	Single	India	ARIES Devasthal Observatory, Nainital, India	2016
Telescopio Nazionale Galileo (TNG)	File:Tng 2001.jpg	Template:Convert	Single	Italy	Roque de los Muchachos Obs., Canary Islands, Spain	1997
New Technology Telescope (NTT)	File:La Silla NTT.jpg	Template:Convert	Single	ESO countries	La Silla Observatory, Coquimbo Region, Chile	1989
Canada-France-Hawaii Telescope (CFHT)	File:Canada-France-Hawaii-Telescope-dome.jpeg	Template:Convert	Single	Canada, France, USA	Mauna Kea Observatories, Hawaii, USA	1979
ESO 3.6 m Telescope	File:Wallpaper of 3.6-m Telescope at La Silla.jpg	Template:Convert	Single	ESO countries	La Silla Observatory, Coquimbo Region, Chile	1977
MPI-CAHA 3.5 m<ref name="autogenerated2004">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || File:Bacares09.jpg || Template:Convert || Single || West Germany, Spain || Calar Alto Obs., Almería, Spain || 1984
USAF Starfire 3.5 m<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>|| | File:Big3 5mtele.png || Template:Convert || Single || USA || Starfire Optical Range, New Mexico, USA || 1994
WIYN Telescope	File:WIYN OBSERVATORY ON KITT PEAK.jpg	Template:Convert	Single	USA	Kitt Peak National Obs., Arizona, USA	1994
Space Surveillance Telescope	File:Space Surveillance Telescope.jpg	Template:Convert	Single	USA, 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)	File:D70050914 15 ApolloLLR.jpg	Template:Convert	Single	USA	Apache Point Obs., New Mexico, USA	1994
Iranian National Observatory (INO340)	File:INO340.png	Template:Convert	Single	Iran	Mount Gargash, Isfahan Province, Iran	2022<ref>Template:Cite news</ref>
Shane Telescope	File:Shane dome.JPG	Template:Convert	Single	USA	Lick Observatory, California, USA	1959
NASA Infrared Telescope Facility	File:Afshin Darian - NASA Infrared Telescope Facility.jpg	Template:Convert	Single	USA	Mauna Kea Observatory, Hawaii, USA	1979
NASA-LMT	File:Liquid Mirror Telescope.jpg	Template:Convert	Liquid	USA	NASA Orbital Debris Obs., New Mexico, USA	citation	CitationClass=web }}</ref>
For continuation of this list, see List of large optical reflecting telescopes

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	File:Grantelescopio.jpg	File:Gran Telescopio Canarias.jpg	10.4	74	36 × 1.9 m hexagons M1 mirror	Segmented mirror	2267
1993–2009	Keck 1	File:KeckTwilight-hi.png	File:KeckObservatory20071013.jpg	10	citation	CitationClass=web }}</ref> || 36 × 1.8 m hexagons M1 mirror || Segmented mirror, M1 f/1.75 || 4145
1976–1993	BTA-6	File:Главная обсерватория.jpg	File:SAO-6m-Telescope-main-mirror.jpg	6	26	605 cm f/4 M1 mirror	Mirror replaced twice	2070
1948–1976	Hale (200 inch)	File:P200 Dome Open.jpg	File:Palomar arp 600pix.jpg	5.1	–	508 cm f/3.3 M1 mirror	Art deco dome	1713
1917–1948	Hooker (100 inch)		File:100inchHooker.jpg	2.54	–		Also used for 1st optical interferometer	1742
For earlier entries, see List of largest optical telescopes historically

File:Telescopes Size and Year Built.png

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).

Future telescopes

Under construction

File:ELT dome reaches its highest point (Tijerales 2).jpg

The Extremely Large Telescope under construction in April 2025

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

• Extremely Large Telescope, Chile – Template:Convert. Construction began in 2018, first light planned in 2028.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• Thirty Meter Telescope, Hawaii, USA – Template:Convert. Construction began in 2014 but halted in 2015; Template:As of it has not resumed.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• 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.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• Vera C. Rubin Observatory, Chile – Template:Convert. First light planned in 2025.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• San Pedro Martir Telescope, Baja California, Mexico – Template:Convert. First light planned in 2023.<ref>Universities in U.S. and Mexico Partner on Telescope Project. Arizona Public Media, 13 November 2017.</ref>Template:Needs update
• Magdalena Ridge Observatory Interferometer, New Mexico, USA – An optical interferometer array with ten Template:Convert telescopes. The light gathering power is equivalent to a Template:Convert single aperture. The first telescope was installed in 2016; construction was paused in 2019 due to insufficient funding<ref>Template:Cite conference</ref> and has not resumed.
• Timau National Observatory, Indonesia – Template:Convert. Construction expected to be completed by early 2025.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

Proposed

File:Comparison of LUVOIR-A and -B primary mirrors with Hubble and JWST.png

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:

• 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>Template:Cite journal</ref>
• Chinese Giant Solar Telescope (CGST), an infrared and optical solar telescope, with light-gathering power equivalent to a 5 m diameter aperture.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref><ref>Template:Cite news</ref>

See also

• List of largest infrared telescopes
• List of telescope types
• Lists of telescopes

Further reading

• Template:Cite journal

External links

• List of large reflecting telescopes
• The World's Largest Optical Telescopes
• Largest optical telescopes of the world
• Selected largest telescopes
• Sidereal Messenger Large refracting telescopes (date 1884)