List of largest optical reflecting telescopes

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Here is a list of the largest optical reflecting telescopes sorted by mirror diameter.

Name	Diameter	Nationality of Sponsors	Site	Built
Southern African Large Telescope (SALT)	11.0 m mosaic	South Africa, USA, UK, Germany, Poland, New Zealand	South African Astronomical Observatory, South Africa	2005
Gran Telescopio Canarias (GTC)	10.4 m mosaic	Spain	Roque de los Muchachos Observatory, Canary Islands	2005
Keck 1	9.8 m mosaic	USA	Mauna Kea Observatory, Hawaii	1993
Keck 2	9.8 m mosaic	USA	Mauna Kea Observatory, Hawaii	1996
Hobby-Eberly Telescope (HET)	9.2 m mosaic	USA, Germany	McDonald Observatory, Texas	1997
Large Binocular Telescope (LBT)	2x8.4 m 2x single	USA, Italy, Germany	Mount Graham International Observatory, Arizona	2004
Subaru (NLT)	8.3 m single	Japan	Mauna Kea Observatory, Hawaii	1999
VLT 1 (Antu)	8.2 m single	ESO Countries (European + Chile)	Paranal Observatory, Chile	1998
VLT 2 (Kueyen)	8.2 m single	ESO Countries (European + Chile)	Paranal Observatory, Chile	1999
VLT 3 (Melipal)	8.2 m single	ESO Countries (European + Chile)	Paranal Observatory, Chile	2000
VLT 4 (Yepun)	8.2 m single	ESO Countries (European + Chile)	Paranal Observatory, Chile	2001
Gemini North	8.1 m single	USA, UK, Canada, Chile, Australia, Argentina, Brazil	Mauna Kea Observatory, Hawaii	1999
Gemini South	8.1 m single	USA, UK, Canada, Chile, Australia, Argentina, Brazil	Cerro Tololo Inter-American Observatory, Chile	2001
Multiple/Magnum Mirror Telescope (MMT)	6.5 m single	USA	Fred Lawrence Whipple Observatory, Arizona	1987 2002
Magellan 1 (Walter Baade)	6.5 m single	USA	Las Campanas Observatory, Chile	2000
Magellan 2 (Landon Clay)	6.5 m single	USA	Las Campanas Observatory, Chile	2002
BTA-6	6 m single	Russia	Zelenchukskaya, Caucasus	1976
Large Zenith Telescope (LZT)	6 m single	Canada, France	Maple Ridge, British Columbia	2003
Hale Telescope	5 m single	USA	Palomar Observatory, California	1948
William Herschel Telescope	4.2 m single	UK, Netherlands, Spain	Roque de los Muchachos Observatory, Canary Islands	1987
SOAR	4.2 m single	USA, Brazil	Cerro Pachón, Chile	2002

Some notes:

• Until MMT in 1980'es, all big telescopes were using single solid primary mirror where material internal strength had to be sufficient to limit deformations caused by its own mass flexing while being moved around.
• The MMT pioneered multiple-mirror technology, but in the end solid mirror making was able to produced single solid mirror for it, and it was rebuilt and recommissioned in 2002.
• The MMT did also teach to the Art of Telescope Making, that oversized protection building (a "dome") is not only overtly expensive thing to do, but does indeed harm overall telescope performance, and thus all new big ones barely fit inside their domes, and those domes are very lightweight structures indeed so that they can quickly cool to night temperatures.
• At several other new telescopes in the late 1980'es, various dynamically computer-controlled support systems were developed for thin and thus "too flexible" mirror plates. First major system commissioned using such was Nordic Optical Telescope which has a) thin mirror (cheap), b) snug fit minimum size dome (cheap), c) az-el mount (cheap), d) big air vents to be opened at night e) adaptive optics, and f) location with excellent seeing conditions, and while it is mere 2.56 m in diameter, it does routinely reach sub-arcsecond angular resolution, which is very close to the diffraction limit of this size telescope.
• At the time of this writing in spring 2006, the limit size of single solid mirror is nearing 9.0 meters.

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http://abell.as.arizona.edu/~hill/list/bigtel99.htm - list of telescopes compiled by John M. Hill, Large Binocular Telescope Observatory, University of Arizonaes:Lista de los mayores telescopios reflectores ópticos fr:Liste des plus grands télescopes