List of largest optical telescopes in the 20th century

The following is a list of the largest optical telescopes in the 20th century, paying special attention to the diameter of the mirror or lens of the telescope's objective, or aperture. Aperture rank currently goes approximately by the usable physical aperture size and not by aperture synthesis, although interferometers attained some of the highest angular resolutions at visible and infrared wavelengths compared to traditional telescopes. Diverging methods of construction and use for reflecting telescopes in that area make comparing synthesized aperture irregular.

The 60 inch telescope, first light in 1908

For instance, Keck I or II alone has less angular resolution than the Keck Interferometer (Keck I & II together), however, the Keck Interferometer is used for a much narrower range of type of observations. Ultimately, a valid comparison between two telescopes must take into consideration more specifications, when a general measurement becomes obtuse.

Aperture of the primary mirror alone can be poor measure of a reflective telescope's significance; for example, the Hubble Space Telescope has only a 2.4 metres (94 in) primary mirror. In addition, many large or significant telescopes are not optical and/or reflecting. However, many famous optical telescopes have had large apertures on their primary mirror with corresponding good angular resolution.

Including optical observatories, including UV, visible and some optical infrared telescopes, near infrared. Covers from about 1901 to 2001, with some flexibility to accommodate ambiguity in classification, for example some 2002 telescope, if it was nearly operation in 2001. 19th century and earlier telescopes that ceased operation are not included, but the list is not complete.

Table of optical telescopes

Multiple mirror telescopes are ranked by their equivalent optical area, not peak interferometric aperture unless it is not relevant for the design. See also List of astronomical interferometers at visible and infrared wavelengths.

See also List of largest optical refracting telescopes, as this list does yet not include such large refractors as the Yerkes Observatory.

Name/Observatory	Aperture m	Aper. in	Mirror type	Nationality of Sponsors	Site and/or Observatory	FL or Built	Image
Keck 1	10 m	394″	Segmented,36	United States	Mauna Kea Observatory, Hawaii	1993
Keck 2	10 m	394″	Segmented,36	United States	Mauna Kea Observatory, Hawaii	1996
Hobby-Eberly Telescope (HET)	9.2 m	362″	Segmented,91	United States, Germany	McDonald Observatory, Texas	1997
Subaru (JNLT)	8.2 m	323″	Single	Japan	Mauna Kea Observatory, Hawaii	1999
VLT 1 (Antu)	8.2 m	323″	Single	ESO Countries + Chile	Paranal Observatory, Chile	1998
VLT 2 (Kueyen)	8.2 m	323″	Single	ESO Countries + Chile	Paranal Observatory, Chile	1999
VLT 3 (Melipal)	8.2 m	323″	Single	ESO Countries + Chile	Paranal Observatory, Chile	2000*
VLT 4 (Yepun)	8.2 m	323″	Single	ESO Countries + Chile	Paranal Observatory, Chile	2001*
Gemini North (Gillett)	8.1 m	318″	Single	United States, Canada, Chile, Australia, Argentina, Brazil	Mauna Kea Obs., Hawaii	1999
Gemini South	8.1 m	318″	Single	United States, Canada, Chile, Australia, Argentina, Brazil	Cerro Pachón, Chile	2001
MMT	6.5 m	256″	Single	United States	F. L. Whipple Obs., Arizona	2000
Magellan 1 (Walter Baade)[1]	6.5 m	256″	Honeycomb	United States	Las Campanas Obs., Chile	2000
Magellan 2 (Landon Clay)	6.5 m	256″	Honeycomb	United States	Las Campanas Obs., Chile	2002*
BTA-6	6 m	238″	Single	USSR + Russia	Zelenchukskaya, Caucasus	1976
Hale Telescope (200 inch)	5.08 m	200″	Single	United States	Palomar Observatory, California	1948
MMT (original) (6 x 1.8 m) optics replaced	4.7 m (6 x 1.8 m)	186″	6 mirrors	United States	F. L. Whipple Obs., Arizona	1979–1998
William Herschel Telescope	4.2 m	165″	Single	UK, Netherlands, Spain	ORM, Canary Islands	1987
SOAR	4.1 m	161″	Single	United States, Brazil	Cerro Pachón, Chile	2002*
Nicholas U. Mayall 4m[2]	4 m	158″	Single	USA	Kitt Peak National Obs.; Arizona	1973
Victor M. Blanco Telescope	4 m	158″	Single	USA	Cerro Tololo Inter-American Obs., Chile	1976
Anglo-Australian Telescope (AAT)	3.89 m	154″	Single	United Kingdom + Australia	Anglo-Australian Obs.; Siding Spring, Australia	1975
United Kingdom Infrared Telescope (UKIRT)	3.8 m	150″	Single IR	United Kingdom	Mauna Kea Observatories; Mauna Kea, Hawaii	1978
3.67m AEOS Telescope (AEOS)	3.67 m	145″	Single	United States	Air Force Maui Optical Station; Haleakala, Hawaii	1996
Telescopio Nazionale Galileo (TNG)	3.58 m	138″	Single	Italy	ORM; La Palma, Canary Islands	1997
New Technology Telescope (NTT)	3.58 m	142″	Single	ESO countries	European Southern Observatory; Cerro La Silla, Chile	1989
Canada-France-Hawaii Telescope (CFHT)	3.58 m	141″	Single	Canada, France, United States	Mauna Kea Observatories, USA	1979
ESO 3.6 m Telescope	3.57 m	140″	Single	ESO countries	European Southern Observatory; Cerro La Silla, Chile	1977
MPI-CAHA 3.5m[3]	3.5 m	138″	Single	West Germany+Spain	Calar Alto Obs., Spain	1984
USAF Starfire 3.5m[4]	3.5 m	138″	Single	USA	Starfire Optical Range; New Mexico	1994
WIYN Telescope	3.5 m	138″	Single	USA	Kitt Peak National Obs., USA	1994
Astrophysical Research Consortium (ARC)	3.48 m	137″	Single	USA	Apache Point Obs.; Sacramento Peak, New Mexico	1994
Shane Telescope	3.05 m	120″	Single	United States	Lick Observatory; Mt. Hamilton, California	1959
Infrared Telescope Facility (IRTF)	3 m	118″	Single IR	United States	Mauna Kea, Hawaii	1979
NASA-LMT (NODO)[5] retired	3 m	118″	Liquid	USA	Sacramento Peak, New Mexico, USA	1995–2002
Harlan J. Smith Telescope	2.72 m	107″	Single	USA	McDonald Observatory, Texas, USA	1969-
UBC-Laval LMT	2.65 m	104″	Liquid	Canada	Vancouver, Canada	1992–
Shajn 2.6m (Crimean 102 in)[6]	2.64 m	103″	Single		Crimean Astrophysical Obs., Ukraine	1961
BAO 2.6	2.6 m	102″	Single		Byurakan Astrophysical Obs.; Mt. Aragatz, Armenia	1976
Nordic Optical Telescope (NOT)	2.56 m	101″	Single	Denmark, Sweden, Iceland, Norway, Finland	La Palma, Canary Islands	1988
Isaac Newton Telescope (INT)	2.54 m	100″	Zerodur	UK	La Palma, Canary Islands moved/new mirror	1984
du Pont	2.54 m	100″	Single	USA	Las Campanas Observatory, Chile	1976
Hooker 100-Inch Telescope	2.54 m	100″	Single	United States	Mt. Wilson Observatory; California	1917
Sloan DSS	2.5 m	98″	Single	United States	Sacramento Peak, New Mexico	1997
Isaac Newton Telescope (INT)	2.54 m	98″	Single	UK	RGO, Sussex, England (original)	1965–1979
Hiltner Telescope[7]	2.4 m	95″	Single	United States	MDM Observatory, Kitt Peak, Arizona	1986
Hubble (HST)	2.4 m	94″	Single	NASA+ESA	Low Earth orbit	1990
Vainu Bappu[8][9]	2.34 m	92″	Single		Vainu Bappu Observatory, India	1986
WIRO 2.3	2.3 m	90.5″	Single	USA	Wyoming, USA	1977
ANU 2.3m ATT[10]	2.3 m	90″	Single	Australia	Siding Spring Obs., Australia	1984
Bok Telescope (90-inch)	2.3 m	90″	Single	USA	Steward Obs., Kitt Peak, Arizona	1969
University of Hawaii 2.2 m[11]	2.24 m	88″	Single	USA	Mauna Kea Observatories, Hawaii	1970[11]
MPIA-ESO (ESO-MPI)	2.2 m	87″	Single	West Germany	Cerro La Silla, Chile	1984[12]
MPIA-CAHA 2.2m[12][13]	2.2 m	87″	Single	West Germany	Calar Alto Observatory, Spain	1979
Xinglong 2.16m[14]	2.16 m	85″	Single	PRC (China)	Xinglong, China	1989
Jorge Sahade 2.15m[15]	2.15 m	84″	Single		Leoncito Astronomical Complex, Argentina	1987
INAOE 2.12 (OAGH)[16]	2.12 m	83″	Single	Mexico, USA	Guillermo Haro Observatory; Sonora	1987
UNAM 2.12	2.12 m	83"	Single		NAO; San Pedro, Mexico	1979
Kitt Peak 2.1-meter	2.1 m	83″	Single	USA	Kitt Peak (KNPO), USA	1964
Otto Struve Telescope	2.1 m	82	Single	USA	McDonald Observatory, USA	1939
Himalayan Chandra Telescope (HCT)[17]	2.01 m	79″	Single	India	Indian Astronomical Obs., Hanle (4500 m)	2000
Alfred Jensch Teleskop	2 m	79″	Single		Karl Schwarzschild Observatory	1960
Carl Zeiss Jena	2 m	79″	Single		Shamakhi Astrophysical Obs., Azerbaijan	1966
Ondřejov 2-m	2 m	79″	Single	USSR + Czechoslovakia	Ondřejov Observatory, Czech	1967
Ritchey-Chretien-Coude (RCC)[18]	2 m	79″	Single		Rozhen Observatory, Bulgaria	1984
Carl Zeiss Jena	2 m	79″	Single		Main Ukraine Obs.
Bernard Lyot Telescope	2 m	79″	Single	France	Pic du Midi Obs., France	1980
Faulkes Telescope South	2 m	79″	Single	UK	Siding Spring Obs., Australia	2001
MAGNUM[19]	2 m	79″	Single IR	Japan	Haleakala Obs., USA	2001
OHP 1.93	1.93 m	76″	Single	France	Haute-Provence Observatory, France	1958
74 inch Radcliffe Telescope (1.9 m)[20]	1.88 m	74″	Single		South African Astronomical Obs., Sutherland, 1974–Present Radcliffe Obs.,1948– 1974[20]	1950
188 cm telescope[21]	1.88 m	74″	Single	Japan	Okayama Astrophysical Observatory, Japan	1960
DDO 1.88 m	1.88 m	74″	Single	Canada	David Dunlap Observatory, Ontario	1935
74" reflector[22]	1.88 m	74″	Single	Australia	Mount Stromlo Observatory, Australia	1955–2003
Kottamia telescope 1.88 m[23][24]	1.88 m	74″	Single	Egypt	Egypt	1960
Vatican Advanced Technology Telescope (VATT)	1.83 m	72″	Single	Vatican City	Mt. Graham International Obs., Arizona	1993[25]
72-Inch Perkins Telescope	1.83 m	72″	Single	USA	Lowell Observatory, Anderson Mesa USA	1964
Plaskett telescope[26]	1.83 m	72″	Single	Great Britain	Dominion Astrophysical Observatory, Canada	1918
Copernico 182 cm[27]	1.82 m	72″	Single	Italy	Asiago Observatory, Italy (1350 m)	1973
1.8m Ritchey Cretien reflector[28]	1.8 m	72″	Single	Korea	Bohyunsan Optical Astronomy Observatory, Korea	1996
Sandy Cross Telescope[29]	1.8 m	71″	Single	Canada	Rothney Astrophysical Observatory	1996
Spacewatch 1.8-meter Telescope[30]	1.8 m	71″	Single	USA	Kitt Peak National Observatory, USA	2001
69-inch Perkins Telescope[31]	1.75 m	69″	Single	USA	Perkins Observatory, Ohio	1931–1964
165 cm telescope	1.65 m	65″	Single		Moletai Astronomical Obs., Lithuania	1991
McMath-Pierce Solar Telescope	1.61 m	63″	Single	USA	Kitt Peak National Obs., USA	1962
AZT-33[32]	1.6 m	63″	Single		Sayan Solar Obs., Siberia (2000m)	1981
1.6 m Perkin Elmer[33]	1.6 m	63″	Single	Brazil	Pico dos Dias Observatory	1981
1.6	1.6 m	63″	R/C	Canada	Mont Mégantic Observatory, Canada	1978
Kaj Strand Telescope[34]	1.55 m	61″	Single	USA	USN Obs. Flagstaff Station,USA	1964
61" Kuiper Telescope	1.55 m	61″	Single	USA	Steward Obs., Mt. Bigelow, USA	1965[35]
Oak Ridge Observatory 61" reflector[36] (Wyeth)	1.55 m	61″	Single	USA	Oak Ridge Observatory, Massachusetts, USA	1933-2005[37]
Estación Astrofísica de Bosque Alegre[38]	1.54 m	60.6″	Single	Argentina	Estación Astrofísica de Bosque Alegre, Argentina	1942
Danish 1.54 meter telescope[39]	1.54 m	60.6″	Single	Denmark	La Silla Observatory, Chile	1979
Harvard 60-inch Reflector[40]	1.524 m	60″	Single	United States	Harvard College Observatory, USA	1905–1931
60-Inch Telescope	1.524 m	60″	Single	United States	Mt. Wilson Observatory; California	1908
Dunn Solar Telescope ex-VTT	1.524 m	60″	Single	USA	National Solar Obs.-Sacramento Peak, USA	1969
Palomar Observatory 60 inch[41]	1.524 m	60″	Single	USA	Palomar Observatory, California, USA	1970
FLWO 1.5m Tillinghast[42]	1.52 m	60″	Single	United States	F. L. Whipple Obs., Arizona	1994
Telescopio Carlos Sánchez (TCS)	1.52 m	60″	Single	UK + Spain	Teide Observatory, Tenerife (Spain)	1971
OHP 1.52	1.52 m	60″	Single	France	Haute-Provence Obs., France	1967
Mt. Lemmon 60" Telescope[43]	1.52 m	60″	Single	USA	Steward Observatory, Mount Lemmon, USA	1970
OAN 1.52 m[44]	1.52 m	60″	Single	Spain	Calar Alto Observatory, Spain	1970s
152 cm G.D. Cassini[45]	1.52 m	60″	Single	Italy	Mount Orzale, Italy	1976
TIRGO (Gornergrat Infrared Telescope)[46]	1.50 m	59″	Single IR	Italy + Switzerland	Hochalpine Forschungsstation Jungfraujoch und Gornergrat, Alps, Switzerland (3150 m)	1979–2005
AZT-22[47]	1.5 m	59″	Single	USSR, Uzbekistan	Mount Maidanak, Uzbekistan	1972
AZT-20[48]	1.5 m	59″	Single		Assy-Turgen Observatory, Kazakhstan[49]
AZT-12[50]	1.5 m	59″	Single	USSR, Estonia	Tartu Observatory, Estonia	1976
RTT-150[51]	1.5 m	59″	Single	Russia, Turkey	TÜBİTAK National Observatory, Turkey	2001
OSN 1.5m (Nasmyth)[52]	1.5 m	59″	Single	Spain	Sierra Nevada Obs., Spain (2896 m)	1991
BST-1M[53]	1.5 m	59″	Single IR	USSR	Salyut 6, Earth Orbit	1977–1982
USNOFS 1.3m[54]	1.3 m	51″	Single	USA	USN Obs. Flagstaff Station,USA	1998
Warsaw Telescope[55]	1.3 m	51″	Single	Poland	Las Campanas Obs., Chile	1996
Skinakas 1.3m Telescope[56]	1.3m	51''	Single	Greece	Skinakas Obs., Greece	1995
McGraw-Hill Telescope[57][58]	1.27 m	50″	Single	USA	MDM Observatory, Arizona (1975–Present) Stinchfield Woods, Michigan (1969–1975)	1969
Great Melbourne Telescope[59] (refit)	127 cm	50″	Single	Australia	Mount Stromlo Observatory, Australia	1961-1973[60] 1992-2003[61]
AZT-11[62]	1.25 m	49″	Single		Abastumani Obs., Georgia (country)	1976
AZT-11[63]	1.25 m	49″	Single		Crimean Astrophysical Obs., Ukraine	1981
MPIA 1.2[64]	1.23 m	48.4″	Single	West Germany + Spain	Calar Alto Obs., Spain	1975
Babelsberg Zeiss[65]	1.25 m	49″	Single	Germany, USSR	Babelsberg Observatory; Berlin, Germany, Crimean Astrophysical Observatory (1952–present)	1924
Galileo 122 cm[66]	1.22 m	48″	Single	Italy	Asiago Observatory, Italy	1942
Samuel Oschin telescope	1.22 m	48″	Schmidt	USA	Palomar Observatory; California	1948
OHP 1.20	1.2 m	48″	Single	France	Haute-Provence Obs., France	1943
Paris 48″ Reflector	1.2 m	48″		France	Paris Observatory, France	1871–1943
Great Melbourne Telescope[67]	122 cm	48″	reflector – metal	Australia	Melbourne Observatory, Australia	1878-1944[68]
Oskar-Lühning Telescope[69]	1.2 m	47″	Single	Germany	Hamburg Observatory, Germany	1975
Leonhard Euler Telescope[70]	120 cm	47″	Single	Switzerland	La Silla, Chile	1998
Mercator Telescope	120 cm	47″	Single	Belgium+Switzerland	ORM; La Palma, Canary Islands	2001[71]
Hamburg Robotic Telescope (HRT)[72]	120 cm	47″	Single	Germany	Hamburg-Bergdorf Obs., Germany	2002*
Hänssgen's reflector[73]	107 cm	42″	Single	Germany	Mobile (~Germany)	2002*
Grubb Parsons 40-inch	102 cm	40″	Single	Sweden	Stockholm Observatory in Saltsjöbaden	1930–present
Nickel Telescope	102 cm	40″	Single	USA	Lick Observatory, USA	1979
Grubb 40-inch	102 cm	40"	Single	USSR	Crimean Astrophysical Observatory Simeiz (destroyed in WWII)	1925–1944
George Ritchey 40-inch (1 m)[74]	102 cm	40″	R/C	USA	Flagstaff, Arizona (Washington, D.C. until 1955)	1934
Yerkes "41-inch"[75]	102 cm	40″	Single	USA	Yerkes Observatory, USA	1968[76]
Meudon Observatory 1m[77]	100 cm	39.4″	Single	France	Meudon Observatory/ Paris Observatory	1891 [78]
ZIMLAT[79]	100 cm	39.4″	Single	Switzerland	Zimmerwald Obs., Switzerland	1997
OGS Telescope[80]	100 cm	39.4″	Single	European Space Agency countries	Teide Observatory, Tenerife (Spain)	1995
Jacobus Kapteyn Telescope	100 cm	39.4″	Single	UK + Netherlands	Isaac Newton Group, Canary Islands	1984
Lulin One-meter Telescope (LOT)[81]	100 cm	39.4″	Single	ROC (Taiwan)	Lulin Observatory, Taiwan	2002*
Zeiss di Merate (1m reflector)	100 cm	39.4″	Single	Kingdom of Italy	Merate Obs., Merate, Italy	1926
Zeiss 1m reflector	100 cm	39.4″	Single	Belgium	Royal Obs., Uccle, Belgium	1920s
Hamburg Spiegelteleskop (1m reflector)[82][83]	100 cm	39.4″	Single	Deutsches Reich (Germany)	Hamburg-Bergdorf Obs., Germany	1911
1-m Carl Zeiss Jena	100 cm	39.4″	Single	CCCP	Assy-Turgen Observatory, Kazakhstan[49]
James Gregory Telescope	94 cm	37"	SCT	Great Britain	University of St Andrews, UK	1962
Schmidt 92/67 cm[84]	92 cm	36″	Schmidt	Italy	Cima Ekar Observatory, Asiago, Italy (1360 m)	1966
Kuiper Airborne Obs.(KAO)	91.4 cm	36″	Single	USA	C-141 (mobile)	1974–1995
Stratoscope 2	91.4 cm	36″	Single	USA	Balloon (mobile)	1961–1973
Crossley Reflector[85]	91.4 cm	36″	Single	US+UK	Lick Observatory, USA	1896[86]
36-inch Yapp reflector	91.44 cm	36″	Reflector	UK	Greenwich & Herstmonceux	1932[87]

This table does not include all the 20th 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 are also known as Mosaic mirrors. Single mirrors, also called monolithic and can be sub-categorized in types, such as solid or honeycomb.

Selected telescopes with apertures of 90 cm (35.4 in.) and smaller

Some famous 20th century regionally famous telescopes, space telescopes, or otherwise significant. (100 cm = 1 meter)

Name	Aperture m	Aper. in	Mirror/type	Nationality/Sponsors	Site	Built/Used
Hopkins Ultraviolet Telescope	90 cm	35.4″	Single UV	USA	STS, Earth Orbit	1990, 1995
Meudon Great Refractor	83cm	32.67"	refractor (visual)	France	Meudon, France	1891
83-cm Reflector, Toulouse Observatory	83cm	32.67"	reflector-glass	France	Toulouse, France	1875[88][89]
Focault 80 cm, Marseille Observatory [90]	80 cm	31.5"	reflector-glass	Focault	Marseille, France	1862-1965[91]
Astron[92]	80 cm	31.5″	Single UV	CCCP + France	Earth orbit	1983–1989[92]
Potsdam Great Refractor (double refractor)	80 cm	31.5 ″	Doublet	Germany	Potsdam, Germany	1899
Ruisinger[93]	76.2 cm	30″	Single-Newtonian	United States (ASKC)	Louisburg, Kansas – Powell Obs.	1985
Greenwich 28 inch refractor Royal Observatory, Greenwich	71 cm	28″	Doublet	British Empire	Greenwich, England Herstmonceux, England	1893
Meudon Great Refractor	62 cm		refractor (photographic-blue)	France	Meudon, France	1891
Infrared Space Observatory	60 cm	23.5″	IR (2.4-240 μm)	European Space Agency	Earth orbit (GEO)	1995–1998
IRAS[94]	57 cm	22.44″	R/C IR	US + UK + The Netherlands	Earth orbit	1983
Mons Telescope	50 cm	19.7″	Single	Belgium	Teide Observatory, Tenerife (Spain)	1972
Dutch Open Telescope (DOT)	45 cm	17.7″	Solar	Denmark	ORM, Canary Islands	1997
Explorer 57 (IUE)	45 cm	17.7″	Single UV	US+UK+ESA Countries	Earth orbit (GEO)	1978–1996
Glazar UV telescope[95]	40 cm	15.75″	Single UV	CCCP	Kvant-1 (Mir), Earth Orbit	1987–2001
Glazar 2 UV telescope[96]	40 cm	15.75″	Single UV	CCCP + Switzerland	Kristall (Mir), Earth Orbit	1990–2001
Mars Global Surveyor—MOC[97]	35 cm	13.8″	R/C	USA	Mars Orbit	1996–2006
Griffith Observatory 12-inch Zeiss refractor[98]	30.5 cm	12"	Achromat	USA	L.A., USA	1931
XMM-Newton—UV camera	30 cm	11.9″	Single UV	ESA Countries	Earth orbit	1998
TRACE	30 cm	11.9″	Single EUV/UV/Vis	NASA	Earth orbit	1998–2010
Hipparcos	29 cm	11.4″	Schmidt	European Space Agency	Earth orbit (GTO)	1989–1993
Astronomical Netherlands Satellite	22 cm	8.7″	Single UV	Nederlands & USA	Earth Orbit	1974–1976
Galileo – Solid State Imager[99]	17.65 cm	6.95″	Reflector	USA	Jupiter	1989–2003
Voyager 1/2, ISS-NAC[100]	17.6 cm	6.92″	Catadioptric	USA	Space	1977
Spacelab IRT[101]	15.2 cm	6″	IR (1.7–118 μm)	ESA + NASA	STS, Earth Orbit	1985
Mariner 10 - TV Photo. (x2)[102]	15 cm	5.9″	Reflector	USA	Space	1973–1975
Deep Space 1—MICAS[103]	10 cm	3.94″	Single	USA	Solar Orbit	1998–2001
Far Ultraviolet Camera/Spectrograph[104][105]	7.62 cm	3″	Schmidt UV	USA	Lunar surface	1972
Voyager 1/2, ISS-WAC[100]	6 cm	2.36″	Lens	USA	Space	1977

At the end of the 20th century preliminary designs for Extremely large telescope of the 21st century were being worked on, as well as many smaller telescopes such as the Large Binocular Telescope

Under Construction

Examples of telescopes that were started in the 20th century, but may only have achieved a preliminary level of construction by the turn of the century.

Name/Observatory	Aperture m	Aper. in	Mirror type	Nationality of Sponsors	Site and/or Observatory	FL or Built
GTC	10.4 m	409″	Segmented,36	Spain (90%), Mexico(5%), USA(5%)	Roque de los Muchachos Observatory, La Palma	2007
Faulkes Telescope North	2 m	79″	Single	UK	Haleakala Observatory, Hawaii	2003[106]

Refractors

Main article: List of largest optical refracting telescopes

See also

• List of largest optical telescopes in the 19th century
• List of largest optical telescopes in the 18th century
• Lists of telescopes
• List of largest optical reflecting telescopes
• List of optical telescopes
  • List of large optical telescopes
• List of largest optical telescopes historically
• List of astronomical interferometers at visible and infrared wavelengths

References

• 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.CS1 maint: multiple names: authors list (link)
• google units calculator

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Further reading

• List of large reflecting telescopes
• The World's Largest Optical Telescopes
• "The Astronomical Scrapbook", Joseph Ashbrook, Sky Publishing Corporation 1984, ISBN 0-933346-24-7
• "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, p. 351
• Sky & Telescope (April 1981) p. 303
• 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"

External links

• List of large reflecting telescopes
• The World's Largest Optical Telescopes
• Largest optical telescopes of the world
• Selected largest telescopes
• Stellafane telescope links