Image: Comparison optical telescope primary mirrors

Description: Comparison of nominal sizes of primary mirrors of notable optical reflecting telescopes, and a few other objects. Dotted lines show mirrors with equivalent light-gathering ability. The telescopes shown in this comparison are listed below, ordered in each sub-section by (effective) mirror/lens area , low to high, and then by actual/planned first light date, old to new. The "present-day" status is given as of July 2020. See also List of largest optical reflecting telescopes. Largest refractors (for comparison): 1) Yerkes Observatory's 40-inch (1.02 m) refractor, 1893 (largest refractor consistently used for scientific observations) 2) Great Paris Exhibition Telescope, 49-inch (1.24 m), 1900 (largest refractor ever built; had practically no scientific usage) Ground-based reflectors: 3) Hooker Telescope, 100-inch (2.5 m), 1917; world's largest telescope from 1917 to 1949 4) Multiple Mirror Telescope, 186-inch (4.72 m) effective, 1979–1998; 6.5 m, from 1998 5) LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope), 4.9 m effective at best, 2009 6) Hale Telescope, 200-inch (5.1 m), 1949; world's largest telescope from 1949 to 1975 7) BTA-6, 6 m, 1975; world's largest telescope from 1975 to 1990 (surpassed by the partially-completed Keck I telescope) 8) Large Zenith Telescope, 6 m, 2003; largest liquid-mirror telescope ever built; decommissioned in 2019 9) Magellan Telescopes, two 6.5‑m individual telescopes, 2000 and 2002; 10) Vera C. Rubin Observatory (formerly Large Synoptic Survey Telescope), 6.68 m effective (8.4‑m mirror, but with a big hole in the middle), planned 2022 11) Gemini Observatory, 8.1 m, 1999 and 2001 12) Subaru Telescope, 8.2 m, 1999; largest monolithic (i.e. non-segmented) mirror in an optical telescope from 1999 to 2005 13) Southern African Large Telescope, 9.2 m effective, 2005 (largest optical telescope in the southern hemisphere) 14) Hobby–Eberly Telescope, 10 m effective, 1996 15) Gran Telescopio Canarias, 10.4 m, 2007 (world's largest single-aperture optical telescope) 16) Large Binocular Telescope, 11.8 m effective (two 8.4‑m telescopes on a common mount), 2005 and 2006; each individual telescope has the largest monolithic (i.e. non-segmented) mirror in an optical telescope, while the combined effective light collecting area is the largest for any optical telescope in non-interferometric mode 17) Keck Telescopes, 14 m effective (two 10‑m individual telescopes), 1993 and 1996; similarly to VLT, the two telescopes were combined only for interferometric observations rather than to simply achieve larger light collecting area; furthermore, this mode has been discontinued 18) Very Large Telescope, 16.4 m effective (four 8.2 m individual telescopes), 1998, 1999, 2000, and 2000; total effective light collecting area would have been world's largest for any present-day optical telescope, but the instrumentation required to obtain a combined incoherent focus was not built 19) Giant Magellan Telescope, 22.0 m effective, planned 2029 20) Thirty Meter Telescope, 30 m effective, planned 2027 21) Extremely Large Telescope, 39.3 m effective, planned 2025 22) Overwhelmingly Large Telescope, 100 m, cancelled Space telescopes: 23) Gaia, 1.45 m × 0.5 m (area equivalent to a 0.96‑m round mirror), 2013 24) Kepler, 1.4 m, 2009 25) Hubble Space Telescope, 2.4 m, 1990 (largest space optical telescope to date) 26) James Webb Space Telescope, 6.5 m effective, planned 2021 Radio telescopes for comparison: 27) Arecibo Observatory's 307‑m dish; largest fully-filled single-aperture telescope from 1963 to 2016 (the largest-aperture telescope of any kind is the very-sparsely-filled RATAN-600 radio telescope) 28) Five-hundred-meter Aperture Spherical [radio] Telescope, 500‑m dish (effective aperture of ≈300 m), 2016; world's largest fully-filled single-aperture telescope from 2016 Other objects for comparison: 29) Human height, 1.77 m on average 30) Tennis court, 78 × 36 ft (23.77 × 10.97 m) 31) Basketball court, 94 × 50 ft (28.7 × 15.2 m)
Title: Comparison optical telescope primary mirrors
Credit: Own work
Author: Cmglee; data on holes in mirrors provided by an anonymous user from IP 71.41.210.146
Usage Terms: Creative Commons Attribution-Share Alike 3.0
License: CC BY-SA 3.0
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