I am telescope. My purpose is to collect as much light as possible from some distant source and deliver it to a detector/observer for detailed study. Different Telescopes opaque opaque Space based telescopes almost opaque transparent Balloons & Rockets Earth based optical telescopes partially transparent Earth based optical and space based telescopes transparent Earth based radio telescopes 1
Reflecting Curved mirrors mirror Refracting Lenses convex lens Focal length focal point Focal length Supported from the back One surface -optics Small tube (small dome) Largest single mirror-10 m No chromatic aberration focal point from the edges two surface -optics long tube (large area) 1 m (40 inch)-yerk Obs chromatic aberration Chromatic aberration in refracting telescopes occur because the lens does not focus different wavelengths of light onto the exact same focal plane (in other words the focal length for different wavelengths is different). The amount of chromatic aberration depends on the dispersion of the glass. For blue light (short wavelengths) refraction or bending is larger than that of red light (long wavelengths). 2
W.M. Keck Observatory Two 10-meter telescopes on Mauna Kea (largest aperture of any single mirror telescope in the world.) Largest refracting telescope (Yerk observatory) Size -- 1 m (40 inch) 3
(Why Larger Size??) 1) Gather more radiation (light gathering power) 2) Get better resolution (resolving power) Collecting area - consider the main objective of a telescope d d = diameter - area increases as d 2 - amount of light increase as d 2 Ex) How much more light does a telescope with d= 200 in. (5 meter) collect compared to the d= ¼ in. eye? Diameter is 200/ ¼ = 800 times larger Telescope collects (800) 2 = 640,000 times more light Resolving power The ability of telescope to separate the objects lying very close together in the sky. Let = smallest angle a telescope can perceive (in theory) 3" Arc sec = 1" = 3" = 5" wavelength( µm) angular resolution = 0.25 diameter( m) larger telescope better resolution longer wavelength poor resolution But, atmospheric turbulence (SEEING) limits ~ 1 or sometimes temperature inside the dome may blur the image. 4
Solutions: 1) Get above atmosphere (Hubble Space Telescope has angular resolution = 0.1 ) 2) New telescope design Active optics corrects the errors in the telescope itself e.g. mechanical fluctuations or change in shape of mirror due to change in temperature. Adaptive optics adjusts mirrors in ground-based telescopes to compensate for atmospheric effects (blurring) NTT (New Technology Telescope) in 1989 at ESO. Focus of telescope is Carefully monitored and controlled by tilting the mirror as its temp or orientation changed. Angular resolution 0.5. Computers modify the mirror thousands of times per sec.gemini and Subaru telescopes have 0.09 and 0.07 angular resolution. NTT constructed in 1989 at the European Southern Observatory in Chile Active Optics on a 3.5-m Telescope 5
Photographic films Photo-multiplier tubes CCD camera (charged couple device) Advantage of CCD over photographic plates : 1) more efficient (90 %) 2) 10 to 20 times fainter 3) less exposure time 4) directly to computers Mountain tops Stable atmosphere relatively free of dust relatively less light pollution moisture free e.g Southwest deserts of United States. Hawii, Arizona 6
A Tour of Astronomical Observatories on the Ground and In Space Compiled by H.A. McAlister January 2001 Some Early Telescopes 4.5 ft One of Galileo s early telescopes c. 1610 (wood and paper with 1-inch aperture) Newton s first reflecting telescope c. 1670 (metal mirror with 2-inch aperture) 7
Early Telescopes Hevelius 140-ft Long Refractor c. 1670 Yerkes Observatory University of Chicago, Williams Bay, WI 40-inch (1-m) telescope is the world s largest refractor installed in 1897. 8
Mount Wilson Observatory Mt. Wilson, CA Mount Wilson Observatory 100-inch Telescope 9
Mount Wilson Observatory 100-inch Dome with Orion Mount Wilson Observatory 150-ft Solar Tower with Comet Hale-Bopp 1997 10
Mount Palomar Observatory Caltech, Mt. Palomar, CA 200-inch (5-m) Hale optical telescope Kitt Peak National Observatory National Science Foundation, Kitt Peak, AZ 11
Kitt Peak National Observatory 4-m Mayall Telescope Kitt Peak National Observatory 4-m Mayall Telescope & Control Room 12
Kitt Peak National Observatory McMath-Pierce Solar Telescopes Kitt Peak National Observatory WIYN Telescope The WIYN Observatory [University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories (NOAO)] has a 3.5 meter telescope with Altitude-Azimuth mount. 13
Cerro Tololo Inter-American Observatory 4-m Telescope at Night Mauna Kea Observatory On the Big Island of Hawaii 8.1-m Gemini North 3.6-m Canada- France-Hawaii NASA infrared Britain s 3.8-m infrared Twin 10-m keck Japanese 8.3- m Subaru MehbZÊ ^_]^[i ]hekdz#xwi[ exi[hlwjeho 14
W.M. Keck Observatory Two 10-meter telescopes on Mauna Kea 10-meters is the largest aperture of any single telescope in the world. W.M. Keck Observatory With NASA Sponsored Interferometer Outriggers 15
Gemini Telescopes Two 8-meter telescopes on Mauna Kea, Hawaii and Cerro Pachon, Chile European Very Large Telescope (VLT) Four 8.2-meter telescopes on Cerro Paranal, Chile (latitude 25 o S) World s largest reflecting telescope having effective area equivalent of a single 16-m mirror. 16
Radio Telescopes The Green Bank Telescope (GBT) at National Radio Astronomy Observatory in West Virginia, 105-m Dish is the World s Largest Fully Steerable Radio Telescope. 17
Arecibo Radio Telescope (300-m diameter) at the National Astronomy and Lonospheric Center is world s largest radio telescope. Constructed in 1963 and upgraded in 1997 to study shorter-wavelength radio radiation. can observe 24 hours a day (darkness is not needed and Sun is weak source) can observe in cloudy nights even in rain or snow storms too. shows whole new picture of the universe. e.g center of Milky Way Galaxy. Disadvantage: unlike optical telescopes, radio detectors register only a narrow band of wavelength at one time. poor resolution. extremely large sizes. (e.g Arecibo telescope cannot follow the object more than few degrees across the sky) 18
Interferometry Two or more radio telescopes are used in tandem to observe the same object at the same wavelength and at the same time. The combined instrument is called interferometer. The effective diameter is the distance between its outermost dishes. The Very Large Array (VLA) National Radio Astronomy Observatory, near Socorro, New Mexico 27 separate dishes spread along Y-shaped pattern about 30 km across on the Plain of San Augustin 19
The Very Long Baseline Array (VLBA) National Radio Astronomy Observatory Kitt Peak Site North America, Europe, Australia and Russia might use the to achieve angular resolution of the order of 0.002. Telescopes in Space Infrared, Ultraviolet, X-ray & Gamma ray astronomy 20
Hubble Space Telescope (Joint project of NASA & ESO) Launched in 1990 Hubble Space Telescope Dimensions: 13 m long; 12 m across; 11,000 kg (12.5 tons) weight, 2.4 m diameter mirror; instruments for optical, ultraviolet and infrared radiation. Orbits Earth about once every 95 min. 21
Far Ultraviolet Spectroscopic Explorer Launched in 1999; captures far ultraviolet radiation (wavelength around 100 nm) Chandra X-ray Observatory Launched in 1999. Boosted by onboard rockets to a much higher elliptical orbit; its farthest point from Earth is 140,000 km (one-third of the way to the moon). 22
A Brief about Space Telescopes Past: Infrared Astronomical Satellite (IRAS): in 1983 (10 month lifetime) Infrared Space Observatory (ISO): Nov 1995 - May 1998 Compton Gamma Ray Observatory (CGRO): 1991 June 2000 Present: Hubble Space Telescope (HST): 1990 --- Far Ultraviolet Spectroscopic Explorer (FUSE): 1999 --- Chandra X-ray Observatory: 1999 --- Future: Space Infrared Telescope Facility (SIRTF): expected to launch sometime in April 2003 (0.85-m mirror operating at 3 to 200 micro m wavelength) Next Generation Space Telescope (recently renamed James Webb Space Telescope) under development Georgia State University s Astronomical Observatories Student Observatory Roof of Urban Life Building on Campus Hard Labor Creek Observatory 50 miles east of Atlanta near Rutledge, Georgia The CHARA Array On Historic Mount Wilson, California 23
GSU s Hard Labor Creek Observatory Rutledge, GA Multiple-Telescope Telescope 16-in Cassegrain Telescope CHARA s Telescope Enclosures Concept & Engineering by Sea West Enterprises, Inc. 24
Installing CHARA s Telescope Enclosures February 1998 CHARA s 1-meter Telescopes 25
CHARA s Beam Synthesis Facility 308-ft long, 12,000 ft 2 area A Building within a Building Thermally & Vibrationally Stabilized Encloses OPLE s & BCL GSU s CHARA Array Mt. Wilson, CA S1 S2 Mark III BSF W2 W1 E2 E1 Aerial Photo by Norm Vargas 26