Largest optical telescopes of the world

By Paul Schlyter, Stockholm, Sweden

Break out of a frame

2003-10-10 First version
2003-12-27 Updated
2004-01-06 Additional info about Herchel's 1.22 m reflector
2005-07-14 Info about future large telescopes updated
2005-11-03 LBT is now operational and I've put it as the world's largest scope here, although it becomes somewhat ambiguous with binocular scopes. SALT is delayed by about half a year.
2006-04-20 TMT added, details added in historical list, Rascine's reference added. Thanks Alan Tokunaga for this info!
2006-07-11 Great Melbourne Telescope added, replacing some other "largest scopes" from that time. Thanks Barry Clark for pointing this out.
2006-10-10 Added Hans Lippershey at the beginning of the list. Thanks Peter Kremer for pointing this out
2008-09-05 Added some more interesting telescopes, and also a short overview of non-optical telescopes.
2009-10-18 Added a pre-Lippershey "telescopic device" with a mirror eyepiece!
2009-10-31 Added some additional info about Herschel's telescopes.
2009-11-02 Added Berlin's big refractor - thanks
2011-12-09 Added info about E-ELT, updated info about telescopes not yet operational.
2011-12-10 Added links to telescope lists at Wikipedia.
2021-10-07 Updated expected opening dates of large telescopes under construction.

Below is a list of the largest optical astronomical telescopes of the world at various times, from the invention of the telescope in 1609 up to the present day. The list is believed to be fairly complete, but for earlier years there may still be some errors. If anyone has any additions or corrections to this list, please email me!

 largest     Aperture  Scope
 scope in     meters

 1580          ?       William Bourne's telescopic device with a lens as objective and a
                       concave mirror as eyepiece!  Didn't understand how it worked,
                       believed magnification depends on the diameter of the lens.
 1608          ?       Hans Lippershey, inventor of the telescope.
 1609         0.016    Galileo - first person to properly observe the skies with a telescope.
 1612         0.026    Galileo.
 1620         0.038    Galileo.
 1638         0.06     Hevelius - Scheiner's helioscope - the first equatorially mounted scope.
 1645         0.12     Hevelius, Danzig.
 1655         0.057    Christian Huygens 12 foot f.l. refractor; discovered Titan.
 1656         0.07     Christian Huygens 23 foot f.l. refractor, x100.
 1672         0.10     Newton (reflector).
 1675         0.13     Hooke (reflector).
 1680?        0.18     Robert Hooke's Gregorian reflector.
 1686         0.19     Constantin Huygens 7.5" 123 foot f.l. air telescope.
 1686         0.20     Constantin Huygens 8"   170 foot f.l. air telescope.
 1686         0.22     Constantin Huygens 8.5" 210 foot f.l. air telescope.
 1690         0.20     Cassini.
 1721         0.15     Halley (reflector).
 1734         0.38     Gregorian reflector by James Short.
 1750         0.50     Gregorian reflector by James Short.
 1752         0.46     Gregorian reflector by James Short, made for the king of Spain.
 1761         0.60     Father Noel (reflector).
 1780-1789    0.75     Rev J. Mitchell's Gregorian reflector,
                         bought, although broken, by Willian Herschel after Mitchell's death.
 1789-1815    1.22     William Herschel's 40 foot f.l. reflector, Bath, England.
                         Last used in 1815, destroyed in a gale 1839.  Frame dismantled by
                         John Herschel 1840 due to rot, then the tube lay in the garden and was
                         crushed by a falling tree in 1870.  Today the original mirror and a
                         quarter of the tube remains.
 1815-1826    0.47     William Herschel's 20 foot f.l. reflector, Bath, England, built in 1783.
                         Restored by William and John Herschel in 1820, then used by
                         John Herschel in South Africa 1834-1838.
 1826-1845    0.91     Lord Rosse's first reflector with 3 foot aperture.
 1845-1878    1.83     Lord Rosse's Leviathan, 6 foot aperture, Birr Castle, Ireland.
                         Last used in 1878, deteriorated rapidly from 1908, dismantled in 1914,
                         mirror moved to Science Museum.  Restored in 1998 with a mirror of
                         aluminium.  One of the original mirror remains at Science Museum,
                         the second original mirror is lost.
 1878-1889    1.22     Great Melbourne Telescope, 4 foot aperture, Melbourne, Australia.
                         Constructed in 1869, remained in Melbourne until the late 1940's. Its
                         building is still intact.  This was the last large reflector with a
                         speculum metal mirror.  It was constructed by, among others, Lord Rosse.
 1889-1908    1.52     A.A. Common's 60-inch reflector; purchased by Harvard University around 1900.
 1908-1917    1.52     60-inch reflector, Mt Wilson, California, USA.
 1917-1948    2.5      Hooker 100-inch reflector, Mt Wilson, California, USA.
 1948-1974    5.0      Hale 200-inch reflector, Palomar Mountain, California, USA.
 1974-1992    6.0      BTA-6, Mt Pashtoukov, Caucasus, Russia.
 1992-2005    9.8      Keck 1, Mauna Kea, Hawaii, USA - twin 9.8 m scopes in separate domes. Keck 2
                       finished in 1996.
 2005 Oct    11.9      LBT (Large Binocular Telescope), Mt Graham, Arizona, USA - 2 x 8.4 m
                       binocular scope.

Constantin Huygens was the brother of the more well-known Christian Huygens.

James Short (1710-1768) was a skilled optician who made at least 1370 telescopes during his lifetime, most of them Gregorian reflectors and some of them the largest telescopes of his time. He was an equally skilled businessman who priced his telescopes so high that only the aristocracy could afford them. These aristocrat dilettants used these telescopes for anything but serious research - therefore, no important astronomical discoveries were made with Short's telescopes. Already at Short's time, high magnification was a selling argument for ignorant buyers; when William Herschel examined one of Short's 12-inch scopes with a claimed magnification of 800x, Herschel found that it actually magnified only 130x.

Not yet operational:
 2027 ?      30   m    TMT (Thirty Meter Telescope), 492 mirrors 1.4 m each.
                         Delayed due to protests about its location on Mauna Kea, Hawaii
 2027 ?      39   m    E-ELT (European Extremely Large Telescope),
                         about 800 mirrors 1.4 m each, secondary mirror 4.2 m
 2029 ?      22   m    GMT (Giant Magellan Telescope, 7 mirrors 8.4 m each
Almost the world's largest scopes:
 1844         0.61 m   William Lassell's 24-inch reflector
 1859-1865    1.22 m   William Lassell's 48-inch reflector (Liverpool, England)
                         While Lassell's reflectors were smaller than Lord Rosse's
                         they were more modern in their design, and had an
                         equatorial mounting.  Lassell moved the 48" to Malta in
                         1861, and never re-erected it upon returning to England
                         in 1865
 1873         0.66 m   26-inch equatorial, USNO, Washington DC, USA
                         Completed in 1873; moved to present site 1893
 1880         0.67 m   Grosse Refractor, Vienna Observatory, Austria
 1886         0.74 m   Lunette Biscoffscheim, Cote d'Azur Observatory, Nice, France
 1888         0.90 m   36-inch Refractor, Lick Observatory, Mt Hamilton, USA
 1889-1999    0.83 m   Grande Lunette, Meudon 33-inch, France.  Europe's largest
                         refractor.  Double refractor: 0.83 m visual, 0.62 m
                         photographic lens.  Out of service since the dome
                         was severely damaged in the great December 1999 storm:
                         now the dome cannot be moved.  It is currently being
                         repaired and renovated and is expected to again become
                         operational in 2004.
 1896         0.68 m   Berlin's big refractor, planned as 1.38 m aperture with 35 m
                         focal length.  The refractor actually built was of 0.68 m
                         aperture and 21 m focal length making it the 8'th biggest
                         refractor in the world, but it is still the longest telescope
                         tube in the world.  It survived WWII.
 1897         1.02 m   Yerkes 40-inch refractor (still the world's largest refractor)
                         with 20 m focal length, Williams Bay, Wisconsin, USA.
 1898         1.57 m   John Peate's 62-inch mirror for the American University
                         Observatory; never mounted in a telescope
 1900         1.25 m   "The great Paris telescope fiasko": 1.25 m lens of
                         57 meter focal length, mounted horizontally with a
                         sidereostat mirror 2 meters large in front of the lens.
                         Disassembled after the Paris exhibition in Nov 1900;
                         the parts were stored at the Paris observatory.
 1917         1.83 m   72-inch Plaskett reflector, Dominion Astrophysical
                         Observatory, Victoria, British Columbia, Canada
                         (first light some months after the Hooker telescope).

 1999         8.2 m    Subaru, a japanese telescope built on Mauna Kea, Hawaii, USA.
                         The word "subaru" is "The Pleiades" in japanese.
 1999         8.2 m    Very Large Telescope, Cerra Paranal, Chile.  Four 8.2 m telescopes.
                         First scope operational in 1999, all four operational in 2000.
 1999         8   m    Gemini North, Mauna Kea, Hawaii, USA.
 2000         6.5 m    MMT (Multiple Mirror Telescope), Mt Hopkins, Arizona, USA.
                         The original MMT had six mirrors 1.8 meters each, creating
                         a total aperture equivalent to a 4.5 meter mirror.  In 2000
                         they were replaced by one single 6.5 meter mirror, but despite
                         this, the telescope kept its original name.
 2002         8   m    Gemini South, the Andes, Chile.
 2005, late  10.4 m    GTC (Gran Telescopio Canarias), La Palma, Canary Islands, Spain
 2006 Aug    11.0 m    SALT (Southern African Large Telescope), Sutherland, South Africa

Some other important historical telescopes
 1616         ?        The very first reflector by Nicolo Zucchi. No secondary mirror
 1663         ?        Gregory's reflector, with a concave secondary mirror
 1671         0.025 m  Newton's reflector, with a flat secondary mirror
 1672         ?        Laurent Cassegrain's reflector, with a convex seconday mirror
 1684         0.10? m  Roemer's transit instrument
 1733         0.064 m  The first achromatic refractor by Chester Moore Hall
 1738         0.15 m   Hadley's f/10 reflector; first modern Newtonian
 1765         ?        The first refractor with a triplet lens, by John Dollond
 1776-1783    0.16 m   William Herschel's 7 foot f.l. reflector; discovered Uranus
 1866         0.45 m   The first large refractor

Telescopes at non-optical wavelengths
Radio telescopes
 1931                  Karl Jansky discovers radio emission from the Milky Way
 1937         9.6 m    First radio telescope with a dish, by Grote Reber
 1957         76  m    Jodrell Bank radio telescope
 1962         91  m    Green Bank radio telescope
 1963        305  m    Arecibo radio telescope - non-steerable
 1971        100  m    Effelsberg radio telescope

IR telescopes
 1979         3.8  m   UKIRT, the world's largest dedicated IR telescope
 1983         0.60     Liquid helium cooled IR telescope onboard the IRAS satellite

UV and X-ray telescopes
 1952                  Hans Wolter outlined grazing incidence telescopes for X-rays
 1962                  First far UV telescope in OSO-1
 1973                  Wolter telescope onboard Skylab studied the solar corona
 1978         0.45 m   UV telescope on the International Ultraviolet Explorer
 1978         0.56     NASA's Einstein Observatory, with a Wolter X-ray telescope
 1983         0.17     ESA's Exosat, with a Wolter X-ray telescope
 1992                  Extreme Ultraviolet Explorer with a Wolter-like telescope
 1999                  Chandra satellite launched, having a Wolter telescope with 0.5" resolution

Links to Wikipedia:
Telescope history Largest refractors Largest reflectors Largest telescopes in 18'th century 19'th century 20'th century

Some early telescope history
Some early telescope history:

Binocular history
Binocular history:

Lots of links related to telescope and binocular history
Lots of links related to telescope and binocular history:

Some historical telescopes
Some historical telescopes:

Herschel museum
Herschel museum:

Lord Rosse's Leviathan
Lord Rosse's Leviathan:

Berlin's big refractor
Berlin's Big Refractor - it does not have any dome!

La Grande Lunette
Reparing and renovating "La Grande Lunette" at Meudon, France; the dome was damaged in a storm 1999 (in French):

Largest telescopes today
Largest telescopes today:

LBT (Large Binocular Telescope) first light in October 2005
LBT (Large Binocular Telescope) first light in October 2005.

Non-web sources:

"The Astronomical Scrapbook", Joseph Ashbrook, Sky Publishing Corporation 1984, ISBN 0-933346-24-7, out of print for years. "The Astronomical Scrapbook" was also a monthly column in Sky and Telescope until 1980. The book contains 91 of the 159 Scrapbooks columns Joe Ashbrook prepared before his sudden death in August 1980.

"Giant Telescopes of the World", Sky and Telescope, August 2000.

"The History of the Telescope", Henry C. King. First published in 1955 by Charles Griffin & Company Ltd; republished by Dover Books in 1979 and again in 2003. The 2003 Dover edition has ISBN 0-486-43265-3 (pbk).

"The Historical Growth of Telescope Aperture", René Racine, Publications of the Astronomical Society of the Pacific, 116:77-83, January 2004