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 especially in astronomy.
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.
| Name | Aperture | Type | Built by | Location | Year | |
| Meter | Inch | |||||
| 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] | 1.26 m | 49.5" | Reflector – metal mirror | William Herschel | Observatory House, England | 1789–1815 |
| John Michell's Gregorian reflector [2] | 75 cm | 29.5" | Reflector – Gregorian | John Michell | Yorkshire, Great Britain | 1780–1789 |
| Father Noel's Gregorian reflector [2] | 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 [3] | 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 [4] | 3.8 cm | 1.5" | Refractor | Galileo Galilei | Italy | 1620 |
| Galileo's 1612 telescope [4] | 2.6 cm | 1" | Refractor | Galileo Galilei | Italy | 1612 |
| Galileo's 1609 telescope [4] | 1.5 cm | 0.62" | Refractor | Galileo Galilei | Italy | 1609 |
| Hans Lippershey's telescope | ? cm | .?" | Refractor | Hans Lippershey | Middelburg, Netherlands | 1608 |
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).
| Name | Aperture | Type | Significance | Location | Year | |
| Meter | Inch | |||||
| 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) [5] | 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) [6] | 102 cm | 40" | glass mirror reflector | First large Ritchey-Chrétien | Flagstaff, Arizona, USA (Washington, D.C. until 1955) | 1934 |
| Plaskett telescope [7] | 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. [8] [9] | 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 [10] | 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; [11] sold, became Crossley Reflector | A. A. Common Reflector, Great Britain / Lick Observatory, California, USA | 1879 |
| Great Melbourne Telescope [12] | 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. [13] | Melbourne Observatory, Melbourne, Australia | 1868–1889 |
| William Lassell 48-inch [14] | 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 [15] | 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." [16] [17] | 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] | 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.) [18] [19] | 47.5 cm | 18.5" | speculum metal mirror reflector | Observatory House, England | 1782 | |
| Reverend John Michell's Gregorian reflector [2] | 75 cm | 29.5" | speculum metal mirror – Gregorian reflector | World's largest 1780 | Yorkshire, Great Britain | 1780–1789 |
| Dollond Apochromatic Triplet [20] | 9.53 cm | 3.75" | Refractor – apochromat | First apochromatic triplet | England | 1763 [20] |
| Father Noel's Gregorian reflector [2] | 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 [21] | 6.4 cm | 2.5" | Refractor – achromat | First achromatic doublet | Great Britain | 1733 |
| Hadley's Reflector [22] | 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 [3] | 18 cm | 7" | speculum metal mirror – Gregorian reflector | First Gregorian | Great Britain | 1674 [23] |
| Newton's Reflector [24] | 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 [21] | Gdańsk (Danzig), Poland | 1638 |
| Galileo's 1620 telescope | 3.8 cm [4] | 1.5" | Refractor | World's largest 1620 | Italy | 1620 |
| Galileo's 1612 telescope | 2.6 cm [4] | 1" | Refractor | World's largest 1612 | Italy | 1612 |
| Galileo's 1609 telescope | 1.5 cm [4] | 0.62" | Refractor | World's largest 1609 | Italy | 1609 |
| Hans Lippershey's telescope | ? cm | .?" | Refractor | World's first recorded telescope | Netherlands | 1608 |
Segmented Mirror (Mosaic) Glass Reflector |
Yerkes Observatory is an astronomical observatory located in Williams Bay, Wisconsin, United States. The observatory was operated by the University of Chicago Department of Astronomy and Astrophysics from its founding in 1897 to 2018. Ownership was transferred to the non-profit Yerkes Future Foundation (YFF) in May 2020, which began restoration and renovation of the historic building and grounds. Re-opening for public tours and programming began May 27, 2022.
The history of the telescope can be traced to before the invention of the earliest known telescope, which appeared in 1608 in the Netherlands, when a patent was submitted by Hans Lippershey, an eyeglass maker. Although Lippershey did not receive his patent, news of the invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In 1611, Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens. By 1655, astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.
A refracting telescope is a type of optical telescope that uses a lens as its objective to form an image. The refracting telescope design was originally used in spyglasses and astronomical telescopes but is also used for long-focus camera lenses. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes, the refracting telescope has been superseded by the reflecting telescope, which allows larger apertures. A refractor's magnification is calculated by dividing the focal length of the objective lens by that of the eyepiece.
An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.
A reflecting telescope is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Many variant forms are in use and some employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a catoptric telescope.
The Newtonian telescope, also called the Newtonian reflector or just a Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton, using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design has made it very popular with amateur telescope makers.
Speculum metal is a mixture of around two-thirds copper and one-third tin, making a white brittle alloy that can be polished to make a highly reflective surface. It was used historically to make different kinds of mirrors from personal grooming aids to optical devices until it was replaced by more modern materials such as metal-coated glass mirrors.
Markree Observatory was an astronomical observatory in County Sligo, Ireland. The asteroid 9 Metis was discovered from this observatory in 1848 by Cooper's assistant Andrew Graham using a comet seeker telescope. The observatory was also home to the largest refractor of the early 1830s, which had a 13.3-inch (340 mm) aperture Cauchoix of Paris lens; the largest in the world at that time. The observatory also housed a number of instruments and was operated to varying degrees throughout the 19th century.
The following timeline lists the significant events in the invention and development of the telescope.
The first reflecting telescope built by Sir Isaac Newton in 1668 is a landmark in the history of telescopes, being the first known successful reflecting telescope. It was the prototype for a design that later came to be called the Newtonian telescope. There were some early prototypes and also modern replicas of this design.
Merate Astronomical Observatory is an old observatory in Merate (Lecco), Italy. It has housed a 1-meter Zeiss telescope since 1926.
An aerial telescope is a type of very long focal length refracting telescope, built in the second half of the 17th century, that did not use a tube. Instead, the objective was mounted on a pole, tree, tower, building or other structure on a swivel ball-joint. The observer stood on the ground and held the eyepiece, which was connected to the objective by a string or connecting rod. By holding the string tight and maneuvering the eyepiece, the observer could aim the telescope at objects in the sky. The idea for this type of telescope may have originated in the late 17th century with the Dutch mathematician, astronomer and physicist Christiaan Huygens and his brother Constantijn Huygens, Jr., though it is not clear if they actually invented it.
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 Greenwich 28-inch refractor is a telescope at the Royal Observatory, Greenwich, where it was first installed in 1893. It is a 28-inch ( 71 cm) aperture objective lens telescope, otherwise known as a refractor, and was made by the telescope maker Sir Howard Grubb. The achromatic lens was made Grubb from Chance Brothers glass. The mounting is older however and dates to the 1850s, having been designed by Royal Observatory director George Airy and the firm Ransomes and Simms. The telescope is noted for its spherical dome which extends beyond the tower, nicknamed the "onion" dome. Another name for this telescope is "The Great Equatorial" which it shares with the building, which housed an older but smaller telescope previously.
Yerkes 41-inch reflector is a 40-inch aperture (101.6 cm) reflecting telescope at the Yerkes Observatory, that was completed in 1968. It is known as the 41 inch to avoid confusion with a 40 inch refractor at the observatory. Optically it is a Ritchey–Chrétien design, and the main mirror uses low expansion glass. The telescope was used as a testbed for an adaptive optics system in the 1990s.
