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), 20 each individual telescope has the largest monolithic (i.e. 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, 19 12) Subaru Telescope, 8.2 m, 1999 largest monolithic (i.e. See also List of largest optical reflecting telescopes.ġ) 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)ģ) 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 (when it was 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, 20 10) Vera C. The 'present-day' status is given as of July 2020. 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. Dotted lines show mirrors with equivalent light-gathering ability. English: Comparison of nominal sizes of primary mirrors of notable optical reflecting telescopes, and a few other objects.

Optical telescope