# List of the largest optical telescopes in North America

This is a list of the largest optical telescopes in North America.

## 21st century

A list of optical telescopes located in North America by aperture.
| Name | Effective aperture m | Aper. in | Mirror type | Nationality / Sponsors | Site | Built |
| Large Binocular Telescope (LBT) | 11.9 m (8.4 m×2) | 330" × 2 | Multiple mirror, 2 | USA, Italy, Germany | Mount Graham International Obs., Arizona, USA | 2004 |
| Hobby–Eberly Telescope (HET) (11 m × 9.8 m mirror) | 10 m | 394" | Segmented, 91 | USA, Germany | McDonald Observatory, Texas, USA | 1997 |
| Subaru (JNLT) | 8.2 m | 323" | Single | Japan | Mauna Kea Observatories, Hawaii, USA | 1999 |
| MMT (1 x 6.5 M1) | 6.5 m | 256" | Single | USA | F. L. Whipple Obs., Arizona, USA | 2000 |
| Hale Telescope (200 inch) | 5.08 m | 200" | Single | USA | Palomar Observatory, California, USA | 1948 |
| MMT (6 × 1.8 m) original optics | 4.7 m (6 × 1.8 m) | 186" | Segmented, 6 | USA | F. L. Whipple Obs., Arizona, USA | 1979–1998 |
| Lowell Discovery Telescope | 4.3 m | 169" | Single | USA | Lowell Observatory, Happy Jack, Arizona | 2012 |
| Daniel K. Inouye Solar Telescope | 4 m | 158" | Single | USA | Haleakala Observatory, Hawaii, USA | 2019 |
| Nicholas U. Mayall 4m | 4 m | 158" | Single | USA | Kitt Peak National Obs., Arizona, USA | 1973 |
| USAF Starfire 3.5 m | 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 |
| 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-LMT retired | 3 m | 118" | Liquid | USA | NASA Orbital Debris Obs., New Mexico, USA | 1995–2002 |
| For telescopes below 3 meters see List of large optical telescopes ||||||||

## Refractors

Some of the big traditional refracting lens telescopes in North America:
| Name/Observatory | Location | Lens diameter | Focal length | Built | Comments |
| Yerkes Observatory | Williams Bay, Wisconsin, USA | 102 cm (40") | 19.4 m (62′) | 1897 | Largest in operation |
| James Lick telescope Lick Observatory | Mount Hamilton, California, USA | 91 cm (36") | 17.6 m | 1888 | |
| William Thaw Telescope Allegheny Observatory | Pittsburgh, Pennsylvania, USA | 76 cm (30") | 14.1 m | 1914 | Brashear made, photographic |
| Leander McCormick Observatory | Charlottesville, Virginia, USA | 66 cm (26") | 9.9 m | 1884 | completed c. 1874, installed 1884 |
| U.S. Naval Observatory | Foggy Bottom Washington, DC, USA moved to Northwest, Washington, D.C., 1893 | 66 cm (26") | 9.9 m | 1873 | Largest refractor in 1873. Alvan Clark & Sons mounting replaced with Warner & Swasey mounting in 1893. |
| Sproul Observatory | Pennsylvania, USA | 61 cm (24") | 11.0 m (36 ft) | 1911 | Currently under restoration to be re-installed in Northwest Arkansas |
| Lowell Observatory | Arizona, USA | 61 cm (24") | 9.75 m (32 ft) | 1894 | Alvan Clark & Sons telescope |

## Biggest telescopes in 1950

Optical telescopes only
| Name / Observatory | Aperture | First Light | Nation |
| Hale Telescope Palomar Obs. | 200 inch 508 cm | 1949 | USA |
| Hooker Telescope Mount Wilson Obs. | 100 inch 254 cm | 1917 | USA |
| McDonald Obs. 82 inch i.e. Otto Struve Telescope | 82 inch 208 cm | 1939 | USA |
| David Dunlap Observatory | 74 inch 188 cm | 1935 | Canada |
| Plaskett telescope Dominion Astrophysical Obs. | 72 inch 182 cm | 1918 | Canada |
| 69-inch Perkins Telescope Perkins Observatory | 69 inch 175 cm | 1931–1964 | USA |
| Wyeth 61" reflector Oak Ridge Observatory | 61 inch 155 cm | 1933–2005 | USA |
| 60 inch Hale Mount Wilson Observatory | 60 inch 152.4 cm | 1908 | USA |

## Biggest telescopes in 1900

| Name/Observatory | Aperture cm (in) | Type | Location then (Original Site) | Extant* |
| Yerkes Observatory | 102 cm (40") | achromat | Williams Bay, Wisconsin, USA | 1897 |
| James Lick telescope, Lick Observatory | 91 cm (36") | achromat | Mount Hamilton, California, USA | 1888 |
| Crossley Reflector | 91.4 cm(36") | reflector – glass | Lick Observatory, California, USA | 1896 |
| Harvard College Observatory | 71 cm (28") | reflector | Cambridge, Massachusetts, USA | 1889 |
| McCormick Observatory | 67 cm (26.37") | achromat | Charlottesville, Virginia, USA | 1883 |
| U.S. Naval Observatory | 66 cm (26") | achromat | Washington, DC, USA | 1873 |
| Lowell Observatory | 61 cm (24") | achromat | Arizona, USA | 1896 |
| Halstead Observatory | 58.4 cm (23") | achromat | Princeton, USA | 1881 |
| Chamberlin Observatory | 50 cm (20") | achromat | Colorado, USA | 1891 |
| 18½-in Dearborn Observatory Refractor | 47 cm (18.5") | achromat | Chicago (1862–1893), Evanston, Illinois (1893), USA | 1862 |
| Flower Observatory | 46 cm (18") | achromat | Philadelphia, USA | 1896 |
| Harvard Great Refractor, Harvard College Observatory | 38 cm (15") | achromat | Cambridge, Massachusetts, USA | 1847 |
| Wellesley College Whitin Observatory 12-inch Fitz Jacob Campbell's 12 inch refractor | 30 cm (12") | achromat | Massachusetts, USA New York, USA | 1900 1852 |
| University of Illinois Observatory | 30 cm (12") | achromat | Urbana, Illinois, USA | 1896 |
| Merz und Mahler (Mitchell cupola), Cincinnati Observatory | 28 cm (11") | achromat | Cincinnati, Ohio, USA | 1843 |
| Fraunhofer Refractor, United States Naval Observatory (Foggy Bottom) | 24.4 cm (9.6") | achromat | Foggy Bottom, D.C., USA | 1844 |
| Wesleyan University 6-inch Lerebours refractor | 15.24 cm (6") | achromat | Connecticut, USA | 1836 |
| Utzschneider & Fraunhofer Comet Seeker | 10.2 cm (4") | acrhomat | Foggy Bottom, D.C., USA | 1843 |

## Biggest telescopes in 1850

Some of the largest at observatories:
| Name/Observatory | Aperture cm (in) | Type | Location then (Original Site) | Extant* |
| Harvard Great Refractor, Harvard College Observatory | 38 cm (15") | achromat | Cambridge, Massachusetts, USA | 1847 |
| Merz und Mahler (Mitchell cupola), Cincinnati Observatory | 28 cm (11") | achromat | Cincinnati, Ohio, USA | 1843 |
| West Point Observatory 9.75 inch Fitz equatorial | 24.77 cm (9.75") | achromat | West Point, USA | 1839 |
| Fraunhofer Refractor, United States Naval Observatory (Foggy Bottom) | 24.4 cm (9.6") | achromat | Foggy Bottom, D.C., USA | 1844 |
| Wesleyan University 6-inch Lerebours refractor | 15.24 cm (6") | achromat | Connecticut, USA | 1836 |
| Yale Dollond 5-inch, Yale College Observatory | 12.7 cm (5") | achromat | New Haven, Connecticut, USA | 1828 |
| Utzschneider & Fraunhofer Comet Seeker | 10.2 cm (4") | acrhomat | Foggy Bottom, D.C., USA | 1843 |