# List of largest optical telescopes historically

Telescopes have grown in size since they first appeared around 1608. The following tables list the increase in size over the years. Different technologies can and have been used to build telescopes, which are used to magnify distant views and gather light (especially important in astronomy).

## By overall aperture

The following is a list of largest single mount optical telescopes sorted by total objective diameter (aperture), including segmented and multi-mirror configurations. It is a historical list, with the instruments listed in chronological succession by objective size. By itself, the diameter of the primary optics can be a poor measure of a telescope's historical or scientific significance; for example, William Parsons, 3rd Earl of Rosse's 72-inch (1.8 m) reflecting telescope did not perform as well (i.e. gather as much light) as the smaller silvered glass mirror telescopes that succeeded it because of the poor performance of its speculum metal mirror.
Optical Telescopes (List by Overall Aperture) :
| Name | Aperture | Aperture | Type | Built by | Location | Year |
| Name | Meter | Inch | Type | Built by | Location | Year |
| Gran Telescopio Canarias (GTC) | 10.4 m | 409" | Reflector – Segmented, 36 | Spain (90%), Mexico, USA | ORM, La Palma, Canary Islands, Spain | 2009 |
| Keck 1 | 10 m | 394" | Reflector – Segmented, 36 | USA | Mauna Kea Observatory, Hawaii, USA | 1993 |
| BTA-6 | 6 m | 238" | Reflector | Soviet Union | Zelenchukskaya, Caucasus | 1976 |
| Hale Telescope | 5.08 m | 200" | Reflector | USA | Palomar Observatory, California, USA | 1948 |
| Hooker Telescope | 2.54 m | 100" | Reflector | USA | Mt. Wilson Observatory, California, USA | 1917 |
| Leviathan of Parsonstown | 1.83 m | 72" | Reflector – metal mirror | William Parsons | Birr Castle, Ireland | 1845 |
| Herschel's 40-foot telescope | 1.26 m | 49.5" | Reflector – metal mirror | William Herschel | Observatory House, England | 1789–1815 |
| John Michell's Gregorian reflector | 75 cm | 29.5" | Reflector – Gregorian | John Michell | Yorkshire, Great Britain | 1780–1789 |
| Father Noel's Gregorian reflector | 60 cm | 23.5" | Reflector – Gregorian | Father Noel | Paris, France | 1761 |
| James Short's Gregorian reflector | 50 cm | 19.5" | Reflector – Gregorian | James Short | Great Britain | 1750 |
| James Short's Gregorian reflector | 38 cm | 14" | Reflector – Gregorian | James Short | Great Britain | 1734 |
| Christiaan Huygens 210 foot refractor | 22 cm | 8.5" | Refractor – Aerial telescope | Christiaan Huygens | Netherlands | 1686 |
| Christiaan Huygens 170 foot refractor | 20 cm | 8" | Refractor – Aerial telescope | Christiaan Huygens | Netherlands | 1686 |
| Christiaan Huygens 210 foot refractor | 19 cm | 7.5" | Refractor – Aerial telescope | Christiaan Huygens | Netherlands | 1686 |
| Hooke's reflector | 18 cm | 7" | Reflector | Robert Hooke | Great Britain | 16?? |
| Hevelius refractor | 12 cm | 4.7" | Refractor | Johannes Hevelius | Gdańsk, Poland | 1645 |
| Hevelius Scheiner's helioscope | 6 cm | 2.3" | Refractor | Johannes Hevelius | Gdańsk, Poland | 1638 |
| Galileo's 1620 telescope | 3.8 cm | 1.5" | Refractor | Galileo Galilei | Italy | 1620 |
| Galileo's 1612 telescope | 2.6 cm | 1" | Refractor | Galileo Galilei | Italy | 1612 |
| Galileo's 1609 telescope | 1.5 cm | 0.62" | Refractor | Galileo Galilei | Italy | 1609 |
| Hans Lippershey's telescope | ? cm | .?" | Refractor | Hans Lippershey | Middelburg, Netherlands | 1608 |

## By historical significance

Chronological list of optical telescopes by historical significance, which reflects the overall technological progression and not only the primary mirror's diameter (as shown in table above).
Optical Telescopes (List by Historical Significance) :
| Name | Aperture | Aperture | Type | Significance | Location | Year |
| Name | Meter | Inch | Type | Significance | Location | Year |
| James Webb Space Telescope | 6.5 m | 256" | Beryllium mirror reflector – Segmented, 18 | Largest space based telescope | Sun–Earth L2 orbit | 2021 |
| Gran Telescopio Canarias (GTC) | 10.4 m | 409" | Reflector – Segmented, 36 | World's largest 2009 | ORM, La Palma, Canary Islands, Spain | 2009 |
| Large Binocular Telescope (LBT) | 8.4 m x 2 (22.8 m LBTI) | 464.5" | glass mirror reflector – Multi-mirror (2) | World's largest 2008 with Beam Combiner | Mount Graham International Observatory, Arizona, USA | 2005 |
| Hobby-Eberly Telescope | 9.2 m | 362" | Reflector – Segmented, 91 | First HET | McDonald Observatory, USA | 1997 |
| Keck 1 | 10 m | 394" | Reflector – Segmented, 36 | World's largest 1993 | Mauna Kea Observatory, Hawaii, USA | 1993 |
| Hubble (HST) | 2.4 m | 94" | glass mirror reflector | Largest Visible-light space based telescope | Low Earth orbit NASA+ ESA | 1990 |
| BTA-6 | 6 m | 238" | glass mirror reflector | World's largest 1976 | Zelenchukskaya, Caucasus | 1976 |
| McMath-Pierce Solar Telescope | 1.61 m | 63" | glass mirror reflector | Largest solar telescope | Kitt Peak National Obs., USA | 1962 |
| Hale Telescope (200 inch) | 5.08 m | 200" | glass mirror reflector | World's largest 1948 | Palomar Observatory, California, USA | 1948 |
| Samuel Oschin telescope | 1.22 m | 48" | glass mirror reflector – Schmidt camera | World's largest Schmidt camera 1948 | Palomar Observatory, California, USA | 1948 |
| George Ritchey 40-inch (1 m) | 102 cm | 40" | glass mirror reflector | First large Ritchey-Chrétien | Flagstaff, Arizona, USA (Washington, D.C. until 1955) | 1934 |
| Plaskett telescope | 1.83 m | 72" | glass mirror reflector | Designed as world's largest but beaten by the 100-inch Hooker telescope | Dominion Astrophysical Observatory, Canada, USA | 1918 |
| Hooker Telescope | 2.54 m | 100" | glass mirror reflector | World's largest 1917 | Mt. Wilson Observatory, California, USA | 1917 |
| Hale 60-Inch Telescope | 1.524 m | 60" | glass mirror reflector | The first of the "modern" large research reflectors, designed and located for precision imaging. | Mt. Wilson Observatory, California, USA | 1908 |
| Great Paris Exhibition Telescope of 1900 | 125 cm | 49.21" | refractor – achromat | Largest refractor ever built, scrapped after Exhibition. | Exposition Universelle (1900), Paris, France | 1900–1901 |
| A. A. Common's 60-inch Ealing reflector | 1.524 m | 60" | glass mirror reflector | World's largest glass mirror reflector 1889, sold to Harvard 1904, moved to South Africa 1920s (Boyden Observatory) where it was largest telescope in the southern hemisphere. | Ealing, Harvard College Observatory, Cambridge, Massachusetts, USA;Boyden Observatory, South Africa | 1889 |
| Yerkes Refractor | 102 cm | 40" | refractor – achromat | Largest operational refractor | Yerkes Observatory, Wisconsin, USA | 1897 |
| A. A. Common's 36 inch Ealing reflector | 91.4 cm | 36" | glass mirror reflector | First to prove fainter than naked eye astrophotography; sold, became Crossley Reflector | A. A. Common Reflector, Great Britain / Lick Observatory, California, USA | 1879 |
| Great Melbourne Telescope | 1.22 m | 48" | speculum metal mirror reflector | Last large reflector with a speculum metal mirror, world's largest equatorially mounted telescope for several decades. | Melbourne Observatory, Melbourne, Australia | 1868–1889 |
| Foucault's telescope | 0.8 m | 31.5" | glass mirror reflector | First metal coated glass mirror telescope | Marseille Observatory, France | 1862 |
| William Lassell 48-inch | 1.22 m | 48" | speculum metal mirror reflector | | Malta | 1861–1865 |
| Rosse telescope: Leviathan of Parsonstown | 1.83 m | 72" | metal – speculum metal mirror reflector | World's largest 1845 | Birr Castle, Ireland | 1845–1908 |
| William Lassell 24-inch | 61 cm | 24" | speculum metal mirror reflector | | Liverpool, England | 1845 |
| Great Dorpat Refractor (Fraunhofer) Dorpat/Tartu Observatory | 24 cm | 9.6" | refractor – achromat | "...the first modern, achromatic, refracting telescope." | Dorpat, Governorate of Estonia | 1824 |
| Rosse 36-inch Telescope | 91.4 cm | 36" | speculum metal mirror reflector | | Birr Castle, Ireland | 1826 |
| Herschel's 40-foot (126 cm d.) | 1.26 m | 49.5" | speculum metal mirror reflector | World's largest 1789 | Observatory House, England | 1789–1815 |
| Herschel's 20-foot (47.5 cm d.) | 47.5 cm | 18.5" | speculum metal mirror reflector | | Observatory House, England | 1782 |
| Reverend John Michell's Gregorian reflector | 75 cm | 29.5" | speculum metal mirror – Gregorian reflector | World's largest 1780 | Yorkshire, Great Britain | 1780–1789 |
| Dollond Apochromatic Triplet | 9.53 cm | 3.75" | Refractor – apochromat | First apochromatic triplet | England | 1763 |
| Father Noel's Gregorian reflector | 60 cm | 23.5" | speculum metal mirror – Gregorian reflector | World's largest 1761 | Paris, France | 1761 |
| James Short's Gregorian reflector | 50 cm | 19.5" | speculum metal mirror – Gregorian reflector | World's largest 1750 | Great Britain | 1750 |
| James Short's Gregorian reflector | 38 cm | 14" | speculum metal mirror – Gregorian reflector | World's largest 1734 | Great Britain | 1734 |
| Chester Moore Hall's Doublet | 6.4 cm | 2.5" | Refractor – achromat | First achromatic doublet | Great Britain | 1733 |
| Hadley's Reflector | 15 cm | 6" | speculum metal mirror reflector | First parabolic newtonian | Great Britain | 1721 |
| Christiaan Huygens 210 foot refractor | 22 cm | 8.5" | Refractor – Aerial telescope | World's largest 1686 | Netherlands | 1686 |
| Christiaan Huygens 170 foot refractor | 20 cm | 8" | Refractor – Aerial telescope | World's largest 1689 | Netherlands | 1686 |
| Christiaan Huygens 210 foot refractor | 19 cm | 7.5" | Refractor – Aerial telescope | World's largest 1686 | Netherlands | 1686 |
| Hooke's reflector | 18 cm | 7" | speculum metal mirror – Gregorian reflector | First Gregorian | Great Britain | 1674 |
| Newton's Reflector | 3.3 cm | 1.3" | speculum metal mirror reflector | First reflecting telescope | England (mobile) | 1668 |
| Hevelius refractor | 12 cm | 4.7" | Refractor | World's largest 1645 | Gdańsk (Danzig), Poland | 1645 |
| Hevelius Scheiner's helioscope | 6 cm | 2.3" | Refractor | World's largest 1638 & First Equatorial | Gdańsk (Danzig), Poland | 1638 |
| Galileo's 1620 telescope | 3.8 cm | 1.5" | Refractor | World's largest 1620 | Italy | 1620 |
| Galileo's 1612 telescope | 2.6 cm | 1" | Refractor | World's largest 1612 | Italy | 1612 |
| Galileo's 1609 telescope | 1.5 cm | 0.62" | Refractor | World's largest 1609 | Italy | 1609 |
| Hans Lippershey's telescope | ? cm | .?" | Refractor | World's first recorded telescope | Netherlands | 1608 |