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.
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.
The list Includes optical observatories, including UV, visible and some optical infrared telescopes, and near infrared. The list covers from about 1901 to 2001, with some flexibility to accommodate ambiguity in classification, for example some 2002 telescopes, if it was nearly operation in 2001. 19th century and earlier telescopes that ceased operation are not included, but the list is not complete.
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] | 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 [9] | 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 [10] | 2.24 m | 88″ | Single | USA | Mauna Kea Observatories, Hawaii | 1970 [10] | |
MPIA-ESO (ESO-MPI) | 2.2 m | 87″ | Single | West Germany | Cerro La Silla, Chile | 1984 [11] | |
MPIA-CAHA 2.2m [11] [12] | 2.2 m | 87″ | Single | West Germany | Calar Alto Observatory, Spain | 1979 | |
Xinglong 2.16m [13] | 2.16 m | 85″ | Single | PRC (China) | Xinglong, China | 1989 | |
Jorge Sahade 2.15m [14] | 2.15 m | 84″ | Single | Leoncito Astronomical Complex, Argentina | 1987 | ||
INAOE 2.12 (OAGH) [15] | 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) [16] | 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 | Czechoslovakia | Ondřejov Observatory, Czechia | 1967 | |
Ritchey-Chretien-Coude (RCC) [17] | 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 [18] | 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) [19] | 1.88 m | 74″ | Single | South African Astronomical Obs., Sutherland, 1974–Present Radcliffe Obs.,1948– 1974 [19] | 1950 | ||
188 cm telescope [20] | 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 [21] | 1.88 m | 74″ | Single | Australia | Mount Stromlo Observatory, Australia | 1955–2003 | |
Kottamia telescope 1.88 m [22] [23] | 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 [24] | |
72-Inch Perkins Telescope | 1.83 m | 72″ | Single | USA | Lowell Observatory, Anderson Mesa USA | 1964 | |
Plaskett telescope [25] | 1.83 m | 72″ | Single | Great Britain | Dominion Astrophysical Observatory, Canada | 1918 | |
Copernico 182 cm [26] | 1.82 m | 72″ | Single | Italy | Asiago Observatory, Italy (1350 m) | 1973 | |
1.8m Ritchey Cretien reflector [27] | 1.8 m | 72″ | Single | Korea | Bohyunsan Optical Astronomy Observatory, Korea | 1996 | |
Sandy Cross Telescope [28] | 1.8 m | 71″ | Single | Canada | Rothney Astrophysical Observatory | 1996 | |
Spacewatch 1.8-meter Telescope [29] | 1.8 m | 71″ | Single | USA | Kitt Peak National Observatory, USA | 2001 | |
69-inch Perkins Telescope [30] | 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 [31] | 1.6 m | 63″ | Single | Sayan Solar Obs., Siberia (2000m) | 1981 | ||
1.6 m Perkin Elmer [32] | 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 [33] | 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 [34] | |
Oak Ridge Observatory 61" reflector [35] (Wyeth) | 1.55 m | 61″ | Single | USA | Oak Ridge Observatory, Massachusetts, USA | 1933-2005 [36] | |
Estación Astrofísica de Bosque Alegre [37] | 1.54 m | 60.6″ | Single | Argentina | Estación Astrofísica de Bosque Alegre, Argentina | 1942 | |
Danish 1.54 meter telescope [38] | 1.54 m | 60.6″ | Single | Denmark | La Silla Observatory, Chile | 1979 | |
Harvard 60-inch Reflector [39] | 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 [40] | 1.524 m | 60″ | Single | USA | Palomar Observatory, California, USA | 1970 | |
FLWO 1.5m Tillinghast [41] | 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 [42] | 1.52 m | 60″ | Single | USA | Steward Observatory, Mount Lemmon, USA | 1970 | |
OAN 1.52 m [43] | 1.52 m | 60″ | Single | Spain | Calar Alto Observatory, Spain | 1970s | |
152 cm G.D. Cassini [44] | 1.52 m | 60″ | Single | Italy | Mount Orzale, Italy | 1976 | |
TIRGO (Gornergrat Infrared Telescope) [45] | 1.50 m | 59″ | Single IR | Italy + Switzerland | Hochalpine Forschungsstation Jungfraujoch und Gornergrat, Alps, Switzerland (3150 m) | 1979–2005 | |
AZT-22 [46] | 1.5 m | 59″ | Single | USSR, Uzbekistan | Mount Maidanak, Uzbekistan | 1972 | |
AZT-20 [47] | 1.5 m | 59″ | Single | Assy-Turgen Observatory, Kazakhstan [48] | |||
AZT-12 [49] | 1.5 m | 59″ | Single | USSR, Estonia | Tartu Observatory, Estonia | 1976 | |
RTT-150 [50] | 1.5 m | 59″ | Single | Russia, Turkey | TÜBİTAK National Observatory, Turkey | 2001 | |
OSN 1.5m (Nasmyth) [51] | 1.5 m | 59″ | Single | Spain | Sierra Nevada Obs., Spain (2896 m) | 1991 | |
BST-1M [52] | 1.5 m | 59″ | Single IR | USSR | Salyut 6, Earth Orbit | 1977–1982 | |
USNOFS 1.3m [53] | 1.3 m | 51″ | Single | USA | USN Obs. Flagstaff Station, USA | 1998 | |
Warsaw Telescope [54] | 1.3 m | 51″ | Single | Poland | Las Campanas Obs., Chile | 1996 | |
Skinakas 1.3m Telescope [55] | 1.3m | 51'' | Single | Greece | Skinakas Obs., Greece | 1995 | |
McGraw-Hill Telescope [56] [57] | 1.27 m | 50″ | Single | USA | MDM Observatory, Arizona (1975–Present) Stinchfield Woods, Michigan (1969–1975) | 1969 | |
Great Melbourne Telescope [58] (refit) | 127 cm | 50″ | Single | Australia | Mount Stromlo Observatory, Australia | 1961–1973 [59] 1992–2003 [60] | |
AZT-11 [61] | 1.25 m | 49″ | Single | Abastumani Obs., Georgia (country) | 1976 | ||
AZT-11 [62] | 1.25 m | 49″ | Single | Crimean Astrophysical Obs., Ukraine | 1981 | ||
MPIA 1.2 [63] | 1.23 m | 48.4″ | Single | West Germany + Spain | Calar Alto Obs., Spain | 1975 | |
Babelsberg Zeiss [64] | 1.25 m | 49″ | Single | Germany, USSR | Babelsberg Observatory; Berlin, Germany, Crimean Astrophysical Observatory (1952–present) | 1924 | |
Galileo 122 cm [65] | 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 [58] | 122 cm | 48″ | reflector – metal | Australia | Melbourne Observatory, Australia | 1878–1944 [59] | |
Oskar-Lühning Telescope [66] | 1.2 m | 47″ | Single | Germany | Hamburg Observatory, Germany | 1975 | |
Leonhard Euler Telescope [67] | 120 cm | 47″ | Single | Switzerland | La Silla, Chile | 1998 | |
Mercator Telescope | 120 cm | 47″ | Single | Belgium+Switzerland | ORM; La Palma, Canary Islands | 2001 [68] | |
Hamburg Robotic Telescope (HRT) [69] | 120 cm | 47″ | Single | Germany | Hamburg-Bergdorf Obs., Germany | 2002* | |
Hänssgen's reflector [70] | 107 cm | 42″ | Single | Germany | Mobile (~Germany) | 2002* | |
Omicron@C2PU | 104 cm | 41" | Single | France | Observatoire de la Côte d'Azur – Calern site, France, IAU code: 010 | 2013 | |
Epsilon@C2PU | 104 cm | 41" | Single | France | Observatoire de la Côte d'Azur – Calern site, France, IAU code: 010 | 2015 | |
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) [71] | 102 cm | 40″ | R/C | USA | Flagstaff, Arizona (Washington, D.C. until 1955), USA | 1934 | |
Yerkes "41-inch" [72] | 102 cm | 40″ | Single | USA | Yerkes Observatory, USA | 1968 [73] | |
Meudon Observatory 1m [74] | 100 cm | 39.4″ | Single | France | Meudon Observatory/ Paris Observatory | 1891 [75] | |
ZIMLAT [76] | 100 cm | 39.4″ | Single | Switzerland | Zimmerwald Obs., Switzerland | 1997 | |
OGS Telescope [77] | 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) [78] | 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) [79] [80] | 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 [48] | ||
James Gregory Telescope | 94 cm | 37" | SCT | Great Britain | University of St Andrews, UK | 1962 | |
Schmidt 92/67 cm [81] | 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 [82] | 91.4 cm | 36″ | Single | US+UK | Lick Observatory, USA | 1896 [83] | |
36-inch Yapp reflector | 91.44 cm | 36″ | Reflector | UK | Greenwich & Herstmonceux | 1932 [84] |
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.
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 | 83 cm | 32.67" | refractor (visual) | France | Meudon, France | 1891 | |
83-cm Reflector, Toulouse Observatory | 83 cm | 32.67" | reflector-glass | France | Toulouse, France | 1875 [85] [86] | |
Focault 80 cm, Marseille Observatory [87] | 80 cm | 31.5" | reflector-glass | Focault | Marseille, France | 1862–1965 [88] | |
Astron [89] | 80 cm | 31.5" | Single UV | CCCP + France | Earth orbit | 1983–1989 [89] | |
Potsdam Great Refractor (double refractor) | 80 cm | 31.5" | Doublet | Germany | Potsdam, Germany | 1899 | |
Ruisinger [90] | 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, UK | 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 [91] | 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 [92] | 40 cm | 15.75" | Single UV | CCCP | Kvant-1 (Mir), Earth Orbit | 1987–2001 | |
Glazar 2 UV telescope [93] | 40 cm | 15.75" | Single UV | CCCP + Switzerland | Kristall (Mir), Earth Orbit | 1990–2001 | |
Mars Global Surveyor —MOC [94] | 35 cm | 13.8" | R/C | USA | Mars Orbit | 1996–2006 | |
Griffith Observatory 12-inch Zeiss refractor [95] | 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 [96] | 17.65 cm | 6.95" | Reflector | USA | Jupiter | 1989–2003 | |
Voyager 1/2, ISS-NAC [97] | 17.6 cm | 6.92" | Catadioptric | USA | Space | 1977 | |
Spacelab IRT [98] | 15.2 cm | 6" | IR (1.7–118 μm) | ESA + NASA | STS, Earth Orbit | 1985 | |
Mariner 10 – TV Photo. (x2) [99] | 15 cm | 5.9" | Reflector | USA | Space | 1973–1975 | |
Deep Space 1 —MICAS [100] | 10 cm | 3.94" | Single | USA | Solar Orbit | 1998–2001 | |
Far Ultraviolet Camera/Spectrograph [101] [102] | 7.62 cm | 3" | Schmidt UV | USA | Lunar surface | 1972 | |
Voyager 1/2, ISS-WAC [97] | 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
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, USA | 2003 [103] |
A primary mirror is the principal light-gathering surface of a reflecting telescope.
A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night.
The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with a primary mirror that measures 8.2 meters in diameter. These optical telescopes, named Antu, Kueyen, Melipal, and Yepun, are generally used separately but can be combined to achieve a very high angular resolution. The VLT array is also complemented by four movable Auxiliary Telescopes (ATs) with 1.8-meter apertures.
The Large Binocular Telescope (LBT) is an optical telescope for astronomy located on 10,700-foot (3,300 m) Mount Graham, in the Pinaleno Mountains of southeastern Arizona, United States. It is a part of the Mount Graham International Observatory.
The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,710-foot (1,740-meter) peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles.
The Paris Observatory, a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its historic building is on the Left Bank of the Seine in central Paris, but most of the staff work on a satellite campus in Meudon, a suburb southwest of Paris.
The Apache Point Observatory is an astronomical observatory located in the Sacramento Mountains in Sunspot, New Mexico, United States, approximately 18 miles (29 km) south of Cloudcroft. The observatory is operated by New Mexico State University (NMSU) and owned by the Astrophysical Research Consortium (ARC). Access to the telescopes and buildings is private and restricted.
The Cerro Tololo Inter-American Observatory (CTIO) is an astronomical observatory located on the summit of Mt. Cerro Tololo in the Coquimbo Region of northern Chile, with additional facilities located on Mt. Cerro Pachón about 10 kilometres (6.2 mi) to the southeast. It is approximately 80 kilometres (50 mi) east of La Serena, where support facilities are located. The principal telescopes at CTIO are the 4 m Víctor M. Blanco Telescope, named after Puerto Rican astronomer Víctor Manuel Blanco, and the 4.1 m Southern Astrophysical Research Telescope, which is situated on Cerro Pachón. Other telescopes on Cerro Tololo include the 1.5 m, 1.3 m, 1.0 m, and 0.9 m telescopes operated by the SMARTS consortium. CTIO also hosts other research projects, such as PROMPT, WHAM, and LCOGTN, providing a platform for access to the southern hemisphere for U.S. and worldwide scientific research.
The Navy Precision Optical Interferometer (NPOI) is an American astronomical interferometer, with the world's largest baselines, operated by the Naval Observatory Flagstaff Station (NOFS) in collaboration with the Naval Research Laboratory (NRL) and Lowell Observatory. The NPOI primarily produces space imagery and astrometry, the latter a major component required for the safe position and navigation of all manner of vehicles for the DoD. The facility is located at Lowell's Anderson Mesa Station on Anderson Mesa about 25 kilometers (16 mi) southeast of Flagstaff, Arizona (US). Until November 2011, the facility was known as the Navy Prototype Optical Interferometer (NPOI). Subsequently, the instrument was temporarily renamed the Navy Optical Interferometer, and now permanently, the Kenneth J. Johnston Navy Precision Optical Interferometer (NPOI) – reflecting both the operational maturity of the facility, and paying tribute to its principal driver and retired founder, Kenneth J. Johnston.
Mount Lemmon Observatory (MLO), also known as the Mount Lemmon Infrared Observatory, is an astronomical observatory located on Mount Lemmon in the Santa Catalina Mountains approximately 28 kilometers (17 mi) northeast of Tucson, Arizona (US). The site in the Coronado National Forest is used with special permission from the U.S. Forest Service by the University of Arizona's Steward Observatory, and contains a number of independently managed telescopes.
An astronomical interferometer or telescope array is a set of separate telescopes, mirror segments, or radio telescope antennas that work together as a single telescope to provide higher resolution images of astronomical objects such as stars, nebulas and galaxies by means of interferometry. The advantage of this technique is that it can theoretically produce images with the angular resolution of a huge telescope with an aperture equal to the separation, called baseline, between the component telescopes. The main drawback is that it does not collect as much light as the complete instrument's mirror. Thus it is mainly useful for fine resolution of more luminous astronomical objects, such as close binary stars. Another drawback is that the maximum angular size of a detectable emission source is limited by the minimum gap between detectors in the collector array.
An extremely large telescope (ELT) is an astronomical observatory featuring an optical telescope with an aperture for its primary mirror from 20 metres up to 100 metres across, when discussing reflecting telescopes of optical wavelengths including ultraviolet (UV), visible, and near infrared wavelengths. Among many planned capabilities, extremely large telescopes are planned to increase the chance of finding Earth-like planets around other stars. Telescopes for radio wavelengths can be much bigger physically, such as the 300 metres aperture fixed focus radio telescope of the Arecibo Observatory. Freely steerable radio telescopes with diameters up to 100 metres have been in operation since the 1970s.
Great refractor refers to a large telescope with a lens, usually the largest refractor at an observatory with an equatorial mount. The preeminence and success of this style in observational astronomy defines an era in modern telescopy in the 19th and early 20th century. Great refractors were large refracting telescopes using achromatic lenses. They were often the largest in the world, or largest in a region. Despite typical designs having smaller apertures than reflectors, great refractors offered a number of advantages and were popular for astronomy. It was also popular to exhibit large refractors at international exhibits, and examples of this include the Trophy Telescope at the 1851 Great Exhibition, and the Yerkes Great Refractor at the 1893 World's Fair in Chicago.
The Nicholas U. Mayall Telescope, also known as the Mayall 4-meter Telescope, is a four-meter reflector telescope located at the Kitt Peak National Observatory in Arizona and named after Nicholas U. Mayall. It saw first light on February 27, 1973, and was the second-largest telescope in the world at that time. Initial observers included David Crawford, Nicholas Mayall, and Arthur Hoag. It was dedicated on June 20, 1973 after Mayall's retirement as director. The mirror has an f/2.7 hyperboloidal shape. It is made from a two-foot thick fused quartz disk that is supported in an advanced-design mirror cell. The prime focus has a field of view six times larger than that of the Hale reflector. It is host to the Dark Energy Spectroscopic Instrument. The identical Víctor M. Blanco Telescope was later built at Cerro Tololo Inter-American Observatory, in Chile.
AMBER, the Astronomical Multi-Beam Recombiner, is an instrument mounted on the Very Large Telescope (VLT), combining the light of the three Unit Telescopes in the near-infrared of the VLT-Interferometer (VLTI). It is at the source of a considerable number of publications in the field of optical long-baseline interferometry.
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