monolithic mirror

A monolithic mirror is a mirror created from a single piece of glass, i.e., typical for small reflector telescopes and the alternative to a segmented mirror for modern large research telescopes. Monolithic mirrors were universal until the latter 20th century, when practical, large segmented mirrors were developed for use in new, larger telescopes. The latter can be made larger, the largest current monolithic mirror being a little more than 8 meters, and monolithic mirrors remain common for telescopes up to that size. Telescopes with sizable monolithic mirrors:

• Anglo-Australian Telescope (AAT).
• Víctor M. Blanco Telescope.
• Large Altazimuth Telescope (BTA-6).
• Canada-France-Hawaii Telescope (CFHT).
• Lowell Discovery Telescope (LDT).
• DKIST.
• ESO 3.6m Telescope.
• European Southern Observatory Very Large Telescope (ESO VLT) (four telescopes).
• Gemini Observatory (two telescopes).
• Hale Telescope.
• Hubble Space Telescope (HST).
• IRTF.
• Large Binocular Telescope (LBT) (can operate as two telescopes, each with a monolithic mirror).
• Rubin Observatory (VRO) (under construction).
• Magellan Telescopes (two telescopes).
• Mayall 4m Telescope.
• MMT (since its 1998 rebuild).
• New Technology Telescope (NTT).
• Shane Telescope.
• SOAR Telescope (SOAR).
• Space Surveillance Telescope (SST).
• Subaru Telescope.
• Telescopio Nazionale Galileo (TNG).
• United Kingdom Infrared Telescope (UKIRT).
• VISTA.
• William Herschel Telescope (WHT).
• WIYN 3.5m Telescope

Example telescopes with segmented mirrors:

• Keck Observatory.
• James Webb Space Telescope (JWST).
• European Extremely Large Telescope (E-ELT) (under construction).