List of largest optical reflecting telescopes



The world's largest optical reflecting telescopes with an aperture diameter of larger than 8 meters (hover with mouse over image).

Legend:
GTC · Keck · Subaru
HET · LBT · VLT
SALT · Gemini (N) · Gemini (S)

This list of the largest optical reflecting telescopes with objective diameters of 3.0 metres (120 in) or greater is sorted by aperture, which is one limit on the light-gathering power and resolution of a reflecting telescope's optical assembly. The mirrors themselves can be larger than the aperture, and telescopes may use aperture synthesis achieved by 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 very high 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 time. Location in the northern or southern hemisphere of the Earth can also limit what part of the sky can be observed.

Table of reflecting telescopes

This list is ordered by optical aperture, which has historically been a useful gauge of limiting resolution, optical area, physical size, and cost. Multiple mirror telescopes that are on the same mount, may have a working beam combiner, and can form an image may be ranked by an equivalent aperture to this reported by sources. HET-style or fixed telescopes are ranked by an equivalent aperture also.

Reflecting telescopes
Name Image Effective aperture
m 		Aper.
in 		Mirror type Nationality / Sponsors Site Built
Gran Telescopio Canarias (GTC) 10.4 m 409″ Segmented, 36 Spain (90%), Mexico, USA Roque de los Muchachos Obs., Canary Islands, Spain 2006/9
Hobby-Eberly Telescope (HET)
11 m × 9.8 m mirror 		10 m [1] 394″ Segmented, 91 USA, Germany McDonald Observatory, Texas, USA 1997
Keck 1 10 m 394″ Segmented, 36 USA Mauna Kea Observatories, Hawaii, USA 1993
Keck 2 10 m 394″ Segmented, 36 USA Mauna Kea Observatories, Hawaii, USA 1996
Southern African Large Telescope (SALT)
11 m × 9.8 m mirror[2] 		9.2 m 362″ Segmented, 91 South Africa, USA, UK, Germany, Poland, New Zealand South African Astronomical Obs., Northern Cape, South Africa 2005
Large Binocular Telescope (LBT)
Phased-array optics for combined 11.9 m[3] 		8.4 m × 2 330″ × 2 Multiple mirror, 2 USA, Italy, Germany Mount Graham International Observatory, Arizona, USA 2004
Subaru (JNLT) 8.2 m 323″ Single Japan Mauna Kea Observatories, Hawaii, USA 1999
VLT UT1 – Antu 8.2 m 323″ Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 1998
VLT UT2 – Kueyen 8.2 m 323″ Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 1999
VLT UT3 – Melipal 8.2 m 323″ Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2000
VLT UT4 – Yepun 8.2 m 323″ Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2001
Gemini North (Gillett) 8.1 m 318″ Single USA, UK, Canada, Chile, Australia, Argentina, Brazil Mauna Kea Observatories, Hawaii, USA 1999
Gemini South 8.1 m 318″ Single USA, UK, Canada, Chile, Australia, Argentina, Brazil Cerro Pachón (CTIO), Coquimbo Region, Chile 2001
MMT (1 x 6.5 m) 6.5 m 256″ Single USA F. L. Whipple Obs., Arizona, USA 2000
Magellan 1 (Walter Baade)[4] 6.5 m 256″ Honeycomb USA Las Campanas Obs., Coquimbo Region, Chile 2000
Magellan 2 (Landon Clay) 6.5 m 256″ Honeycomb USA Las Campanas Obs., Coquimbo Region, Chile 2002
BTA-6 6 m 238″ Single USSR/Russia Special Astrophysical Obs., Karachay–Cherkessia, Russia 1975
Large Zenith Telescope (LZT) 6 m 236″ Liquid Canada, France, United States [5] Maple Ridge, British Columbia, Canada 2003
Hale Telescope (200 inch) 5.08 m 200″ Single USA Palomar Observatory, California, USA 1948
LAMOST (6.67 m × 6.05 m + 5.72 m × 4.40 m corrector; effective aperture 3.6–4.9 m) 4.9 m–3.6 m [6] 193″ Segmented
(37 + 24)[7] 		PRC (China) Beijing Astronomical Obs., Xinglong, China 2008
MMT (original optics: 6 × 1.8 m)
→see above record for current 6.5 m mirror 		4.7 m
(6×1.8 m) [8] 		186″ Segmented, 6 USA F. L. Whipple Obs., Arizona, USA 1979–1998
Discovery Channel Telescope[9] 4.3 m 169″ Single USA Lowell Observatory, Happy Jack, Arizona, USA 2012
William Herschel Telescope 4.2 m 165″ Single UK, Netherlands, Spain Roque de los Muchachos Obs., Canary Islands, Spain 1987
SOAR 4.1 m 161″ Single USA, Brazil Cerro Pachón (CTIO), Coquimbo Region, Chile 2002
VISTA 4.1 m 161″ Single ESO Countries, Chile Paranal Observatory, Antofagasta Region, Chile 2009
Victor M. Blanco Telescope 4 m 157″ Single USA Cerro Tololo Inter-American Obs., Coquimbo Region, Chile 1976
Nicholas U. Mayall 4 m[10] 4 m 158″ Single USA Kitt Peak National Obs., Arizona, USA 1973
Anglo-Australian Telescope (AAT) 3.89 m 154″ Single Australia, UK Australian Astronomical Obs., New South Wales, Australia 1974
3.67 m AEOS Telescope (AEOS) 3.67 m 145″ Single USA Air Force Maui Optical Station, Hawaii, USA 1996
3.6 m Devasthal Optical Telescope[11] (DOT) 3.60 m 141″ Single India ARIES Devasthal Observatory, Nainital, India 2016
Telescopio Nazionale Galileo (TNG) 3.58 m 138″ Single Italy Roque de los Muchachos Obs., Canary Islands, Spain 1997
New Technology Telescope (NTT) 3.58 m 142″ Single ESO countries La Silla Observatory, Coquimbo Region, Chile 1989
Canada-France-Hawaii Telescope (CFHT) 3.58 m 141″ Single Canada, France, USA Mauna Kea Observatories, Hawaii, USA 1979
ESO 3.6 m Telescope 3.57 m 140″ Single ESO countries La Silla Observatory, Coquimbo Region, Chile 1977
MPI-CAHA 3.5 m[12] 3.5 m 138″ Single West Germany, Spain Calar Alto Obs., Almería, Spain 1984
USAF Starfire 3.5 m [13] 3.5 m 138″ Single USA Starfire Optical Range, New Mexico, USA 1994
WIYN Telescope 3.5 m 138″ Single USA Kitt Peak National Obs., Arizona, USA 1994
Space Surveillance Telescope 3.5 m 138″ Single USA White Sands Missile Range, New Mexico, USA 2011
Astrophysical Research Consortium (ARC) 3.48 m 137″ Single USA Apache Point Obs., New Mexico, USA 1994
Shane Telescope 3.05 m 120″ Single USA Lick Observatory, California, USA 1959
NASA Infrared Telescope Facility 3.0 m 120″ Single USA Mauna Kea Observatory, Hawaii, USA 1979
NASA-LMT
→retired, private[14] 		3 m 118″ Liquid USA NASA Orbital Debris Obs., New Mexico, USA 1995–2002
See List of large optical reflecting telescopes for continuation of list

There are only a few sites capable of polishing the mirrors for these telescopes. SAGEM in France polished the four VLT mirrors, the two Gemini mirrors, and the 36 segments for GTC.[15] The Steward Observatory Mirror Lab cast and polished the two LBT mirrors, the two Magellan mirrors and the MMT replacement mirror. It is currently making the LSST primary mirror and the mirrors for the Giant Magellan Telescope.[16] The Keck segments were made by Schott AG. The SALT and LAMOST segments were cast and polished by LZOS.[17] The mirror for Subaru was cast by Corning and polished at Contraves Brashear Systems in Pennsylvania.[18]

This table does not include all the largest mirrors manufactured. The Steward Observatory Mirror Lab produced the 6.5-metre f/1.25 collimator used in the Large Optical Test and Integration Site of Lockheed Martin, used for vacuum optical testing of other telescopes.

Segmented mirrors are also referred to as mosaic mirrors. Single mirrors are also referred to monolithic mirrors, and can be sub-categorized in types, such as solid or honeycomb.

Comparison of nominal sizes of apertures of some notable optical telescopes
For the largest reflecting telescopes on the planet, the horizontal indicates the year built and the vertical direction indicates the size of the mirror measured in meters. Countries which contain several of these telescopes are color-coded for identification.

Top telescopes of 2010

The largest telescopes are multi-telescope interferometers, and may have longer baselines. However, these astronomical interferometers are less flexible in use, and many interferometers cannot form images or see faint objects despite their high peak angular resolution.

The largest telescope during the first decade of the 21st century could be either the Gran Telescopio Canarias (one 10.4 m diameter mirror), the Large Binocular Telescope (two 8.4 m diameter mirrors on a binocular mount), or the Very Large Telescope (with four 8.2 m telescopes and four 1.8 m auxiliary telescopes). However, as these were still coming online in the period, the two 10 m Keck Telescopes (with 85 m aperture synthesis) were possibly the largest in full scientific operation.

Note other wavelengths of telescopes can be much larger physically, such as the 305 m aperture Arecibo radio telescope, but since radio wavelengths are also larger, this does not necessarily translate into brighter or higher resolution images.

Reflecting telescopes (2010)
Name Out In Aperture (m) Equiv. Area (m) Area (m2) Mirrors Note Altitude (m)
Gran Telescopio Canarias (GTC) 10.4 10.4 74 36 × 1.9 m hexagonal segments for M1 Commissioned 2009; Largest single mirror 2267
Southern African Large Telescope (SALT) 11 (max.) 9.2 66–45 92 × 1 m hexagon; 11 × 9.8 m mirror HET twin but larger optically. Spherical M1 w/ fixed mirror; spectroscopy (see here ) 1783
Keck 1 & 2 10 m each 10 76 (each)[19] 36 × 1.8 m hexagons M1 mirrors each largest twin telescopes
152 m2 total optical area 		4145
VLT 1, 2, 3 & 4 8.2 (each) 8.2 53 (each)
1 x 8.2 m M1 each Largest quadruplet telescope
210 (total optical area) 		2635
Large Binocular Telescope (LBT) 8.4 m each 11.7 111 (both sides) 2 x 8.4 m M1 mirrors; 1 mount Largest Binocular; largest non-segmented mirrors; 22.8 m aperture planned [20] 3221

Largest telescopes with interferometer mode, and two image-forming interferometer arrays.

Reflecting telescopes (with interferometer mode)
Name Longest baseline (m) Mirrors Area (m2) Equiv. Note
VLTI 200 4 × 8.2 m (VLT 1,2,3, & 4) 210 [21] 16 Behind schedule in 2010, 4 units at 130 m success in 2012[22]
Keck Interferometer 85 2 × 10 m (Keck 1 & 2) 152[21] Operations ceased in 2012.[23]
Large Binocular Telescope (LBTI) 22.8* 2 × 8.4 m 110 [21] 11.9 One telescope mount*; Fizeau & Amplitude Interferometry
CHARA array 330 6 × 1 m 2.45 [24]
NPOI 437 6 siderostats (visible) Sparse Aperture [21] Optically resolved Mizar (star)

*Baseline does not reduce with viewing angle

Top telescopes of 2000

Reflecting telescopes (2000)
Name Out In Aperture (m) Area (m2) Mirrors Note Altitude (m)
Keck 1 & 2 10 (each) 76 (each)[19] 36 × 1.8 m hexagons M1 mirrors each largest twin telescopes, largest aperture mirrors, 152 m2 total optical area 4145
Hobby-Eberly Telescope (HET) 9.2 (max.) 66–45 92 x 1 m hexagon; 11 × 9.8 m mirror Spherical M1 w/ fixed mirror; spectroscopy 2030
Subaru Telescope 8.2 53 1 × 8.3 m M1 Largest single piece mirror (tied with the 4 VLT) 4145
UT1 – Antu 8.2 53 1 x 8.2 m M1 Part of a quadruplet telescope setup 2635
UT2 – Kueyen 8.2 53 1 x 8.2 m M1 Part of a quadruplet telescope setup 2635
UT3 – Melipal 8.2 53 1 x 8.2 m M1 Part of a quadruplet telescope setup 2635
Under construction
Reflecting telescopes (2000)
Name Out In Aperture (m) Area (m2) Mirrors Note Altitude (m)
VLT 1, 2, 3 8.2 (each) 53 (each) 1 x 8.2 m M1 By the year 2000 three unit telescopes were online; each were the largest single piece mirrors at that time (tied with Subaru) 2635

Chronologically

Reflecting telescopes (chronologically)
Years Largest Name Out In Aperture (m) Area (m2) M1 Mirror Note Altitude (m)
2009–Present Gran Telescopio Canarias 10.4 74 36 × 1.9 m hexagons M1 mirror Segmented mirror 2267
1993–2009 Keck 1 10 76 [19] 36 × 1.8 m hexagons M1 mirror Segmented mirror, M1 f/1.75 4145
1976–1993 BTA-6 6 26 605 cm f/4 M1 mirror Mirror replaced twice 2070
1948–1976 Hale (200 inch) 5.1 – 508 cm f/3.3 M1 mirror Art deco dome 1713
1917–1948 Hooker (100 inch) 2.54 – Also used for 1st optical interferometer 1742

For earlier top telescopes see List of largest optical telescopes historically

Future telescopes

Sketch of the Messier 51 by William Parsons in 1845, later known as the Whirlpool Galaxy
Whirlpool Galaxy (M51A/B or NGC 5194/5) by NASA/ESA from Hubble Space Telescope in 2005

Below are selected telescopes that are still in the conceptual/proposed stage or still under construction.

Under construction or planned construction

Proposed

See also

References

  1. ↑ "Upgraded Hobby-Eberly Telescope Sees First Light | McDonald Observatory". mcdonaldobservatory.org. Retrieved 2016-07-29.
  2. ↑ "Howstuffworks "10 Amazing Telescopes"". Science.howstuffworks.com. Archived from the original on December 22, 2008. Retrieved August 19, 2009.
  3. ↑ 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
  4. ↑ "The Carnegie Observatories – Magellan Telescopes". Carnegie Institution for Science. Retrieved 2017-05-24.
  5. ↑ The Telescope, By Geoff Andersen, Page 165
  6. ↑ Archived July 22, 2011, at the Wayback Machine.
  7. ↑ "LAMOST Homepage – Gallery". Lamost.org. June 22, 2008. Retrieved August 19, 2009.
  8. ↑ Dwayne DayMonday, May 11, 2009 (2009-05-11). "Mirrors in the dark". The Space Review. Retrieved 2012-01-03.
  9. ↑ Lowell Observatory - DCT status
  10. ↑ "The Mayall 4-Meter Telescope". Noao.edu. February 27, 1973. Retrieved August 19, 2009.
  11. ↑ Sagar, Ram; Brijesh Kumar; Amitesh Omar; A. K. Pandey (2012). "New optical telescope projects at Devasthal Observatory". Proceedings of the Society of Photo-Optical Instrumentation Engineers. 8444. Bibcode:2012SPIE.8444E..1TS. arXiv:1304.2474 Freely accessible. doi:10.1117/12.925634.
  12. ↑ "Max-Planck-Institut für Astronomie". Mpia.de. July 20, 1994. Retrieved August 19, 2009.
  13. ↑ John Pike. "Starfire". Globalsecurity.org. Retrieved August 19, 2009.
  14. ↑ "NASA Orbital Debris Observatory". Astro.ubc.ca. Retrieved August 19, 2009.
  15. ↑ "Polissage Optique pour les Grands Instruments de la Physique et de l ’Astronomie" (PDF).
  16. ↑ "Mirror Castings". Steward Observatory Mirror Lab.
  17. ↑ "Large Optics Manufacturing in Large Optics Manufacturing in Lytkarino Optical Glass Factory, Russia" (PDF).
  18. ↑ "SUBARU Telescope 8.3m Primary Mirror Finished".
  19. 1 2 3 "Keck Telescope Facts". Spacecraftkits.com. Retrieved 2012-01-03.
  20. ↑ "Archived copy". Archived from the original on 2010-08-19. Retrieved 2010-08-16.
  21. 1 2 3 4 "Telescope - Modern Optical Telescopes - Mirror, Diameter, Keck, and Honeycomb - JRank Articles". Science.jrank.org. Retrieved 2012-01-03.
  22. ↑ K. Moskvitch - Four telescope link-up creates world's largest mirror (2012) - BBC
  23. ↑ KI
  24. ↑ "Large Telescopes". Astro.nineplanets.org. Retrieved 2012-01-03.
  25. ↑ "Groundbreaking for the E-ELT (eso1419 — Organisation Release)". ESO. 19 June 2014. Retrieved 3 January 2015.
  26. ↑ Stewart, Burnett, Colin M., John (October 14, 2016). "Hawaii Supreme Court voids Thirty Meter Telescope permit". Oahu Publications. West Hawaii Today. Retrieved 19 December 2015.
  27. ↑ "GMT – Overview". Gmto.org. Retrieved 2017-05-24.
  28. ↑ Amos, Jonathan (12 November 2015). "Giant Magellan Telescope: Super-scope project breaks ground". BBC News. Retrieved 2015-11-15.
  29. ↑ "International Liquid Mirror Telescope – Extragalactic Astrophysics and Space Observations". Aeos.ulg.ac.be. Retrieved August 19, 2009.
  30. ↑ CAPI Report (in Spanish). Nov. 4,2013
  31. ↑ "Introduction to the Chinese Giant Solar Telescope" (PDF).
  32. ↑ Staff (29 August 2012). "China Exclusive: Scientists looking for site for giant solar telescope". Retrieved 8 December 2014.

Further reading

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