General Information

• How Telescopes Work at howstuffworks.com.
• Space.com: Reference pages and page on uses of telescopes.

History and Future Plans

• List of the world's largest optical telescopes.
• Galileo Project pages on Hans Lipperhey and Early telescopes.
• Year 2000 report on plans and priorities.
• Virtual Observatories: AVO (Astrophysical Virtual Observatory) site; IVOA (International Virtual Observatory Alliance) site; Research article.

Special Techniques

• Imperial College Applied Optics Research page.
• Active Optics: Gemini North page; L. Noethe article.
• Adaptive Optics: Mt Wilson page; Gemini North page; Center for Adaptive Optics site.
• CCD Photography: Thierry Legault's page.

Present Ground-Based Telescopes

• CHARA (Center for High Angular Resolution Astronomy): Optical Interferometer array on Mt Wilson.
• Gemini North: On Mauna Kea, Hawaii; Started operations in 2001; Uses adaptive optics.
• Gemini South: Atop Cerro Pachon, Chile, identical to Gemini North.
• Keck I and II: Twin telescopes, atop Mauna Kea in Hawaii; each a 10-m diameter array of individual hexagonal mirrors, using adaptive optics (see also the Keck Interferometer).
• Magellan: Twin 6.5-meter telescopes of the Carnegie Observatories in Cerro Las Campanas, Chile, in partnership with various US universities. Designing and construction started in 1993; the first telescope saw first light in 2000.
• MMTO (Multiple Mirror Telescope): Initially 6 1.8-m mirrors, now a single 6.5-m mirror (the largest, as of 05.00), atop Mount Hopkins in Arizona, uses adaptive optics and optical-fiber-fed spectrographs; started operation in 2000.
• Mt Palomar 200": The largest telescope for about 40 years after its inauguration in 1948.
• Mt Wilson 100": The largest telescope until the Mt Palomar 200" Hale telescope was inaugurated.
• PTI (Palomar Testbed Interferometer): Designed to test the feasibility of using optical interferometry in theground-based search for extrasolar planets, and to initiate a small search for them.
• USNO (US Naval Observatory).

Future Ground-Based Telescopes

• CELT (California Extremely Large Telescope): In the early planning stages by the University of California and Caltech; a 30-m diameter array of hexagonal mirrors, using adaptive optics-similar to the Keck telescopes.
• KAIT (Katzman Automatic Imaging Telescope): An entirely automated 76-cm diameter reflecting telescope equipped with a CCD camera and automatic guider, located at Lick Observatory atop Mount Hamilton just East of San Jose, California, and dedicated for the search for supernovae and the monitoring of celestial objects.
• LBT (Large Binocular Telescope): Two 8.4 m mirrors on a single mount, located atop Mount Graham in Arizona, to be completed in 2004; updates from May 2000, Dec 2002, Oct 2004.
• NPOI (Navy prototype Optical Interferometer).
• OWL (Overwhelmingly Large telescope): In the early planning stages by the ESO; a 100-m diameter array.
• NPOI (Navy Prototype Optical Interferometer): Not yet fully operational, will be able to see features on stars.
• SALT (Southern African Large Telescope): With a segmented mirror 11 meters wide, it will be the most powerful optical-infrared telescope in the Southern Hemisphere; expected to be completed in 2004.
• SOAR (SOuthern Astrophysical Research Telescope): A 4.2-m optical/infrared telescope to be built in Chile; main mirror is now being polished.
• VLT (Very Large Telescope): A quartet of 8.2-m telescopes (Antu, Kueyen, Melipal, and Yepun) and 3 smaller ones atop Cerro Paranal in Chile; the quartet saw first light in May 1998, March 1999, January 2000, and September 2000, respectively. The combined mirror surface of the foursome totals more than 210 square meters.

Space-Based Telescopes

• Hipparchos: ESA space astrometry mission; Launched in 1989, operated until 1993.
• Hubble Space Telescope: Launched in 1990 aboard the space shuttle Discovery, improved and mirror repaired in orbit in 1993 and 1997, observes visible light and, to a lesser degree, ultraviolet and infrared radiation (How Stuff Works page).
• SIM (NASA's Space Interferometry Mission): Scheduled for launch in 2009.
• JWST (James Webb Space Telescope, formerly known as Next Generation Space Telescope): NASA/ESA orbiting telescope scheduled for launch in 2010; 100 to 600 times as sensitive as the Hubble Space Telescope, and two to three times as large; For very high redshift studies.
• TPF (Terrestrial Planet Finder): Using space interferometry, launch planned for 2011.
• GAIA: ESA space-based mission which will analyse the composition, formation and evolution of our Galaxy by mapping with unprecedented precision one billion stars (as well as asteroids, near Earth objects, extrasolar planets, and other objects); to be launched no later than 2012.