A Tour of Astronomical

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A Tour of Astronomical Observatories on the
Ground and In Space Compiled by H.A. McAlister
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But First, A Little Bit About Light
The light we see with our eyes is a form of
electromagnetic radiation which propagates
through space at the speed of light c where c
300,000 km/sec ( 186,000 mi/sec). This
radiation exists in the form of a wave that is
characterized by its wavelength l and
frequency n such that lxn c.
l
l
Propagation direction
c
l
n is the number of waves that pass a fixed point
in one second
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The Electromagnetic Spectrum Visible Light
Invisible Region (long ls)
Infrared
Red
Orange
Incident White Light
Yellow
n
Visible Region Roy G. Biv
Green
Blue
Glass Prism
Indigo
Violet
l
Ultraviolet
Energy
Invisible Region (short ls)
Screen
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The Electromagnetic Spectrum Complete Spectrum
Region g-rays X-rays Ultraviolet Visible Light
Infrared Microwave Radio
l (meters) lt10-12 10-11 10-8 0.4x10-6-
0.7x10-6 10-5 10-3 gt 10-3
n (Hertz) gt1020 1018 1016 1014 1013 1011 lt
1011
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Astronomical Telescopes Refracting Telescopes
fo
fe
Incoming Starlight
Eyepiece
Observer
Focus
Refracting Objective Lens (convex)
fo
Magnifying Power
fe
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Astronomical Telescopes Newtonian Reflecting
Telescopes
Secondary Mirror (flat)
Incoming Starlight
Reflecting Objective Mirror (concave)
Focus
Observer
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Astronomical Telescopes Light Gathering Power
The amount of light collected by a telescope is
proportional to the area of the telescopes
objective lens or mirror. The diameter of the
objective is known as the aperture (A) of the
telescope. Remember that the area of a circle
is given by pr2 or p(A/2)2 in the case of a
telescope whose aperture is A.
Objective 1
Objective 2
Thus, we can compare the light gathering power
(LGP) of two telescopes using
LGP1 p(A1/2)2


(A1/A2)2
(10/1)2 100 for the case of the 10-m
Keck telescope compared
with the 1-m Yerkes
telescope.

LGP2 p(A2/2)2
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Some Early Telescopes
4.5 ft
One of Galileos early telescopes c. 1610 (wood
and paper with 1-inch aperture)
Newtons first reflecting telescope c.
1670 (metal mirror with 2-inch aperture)
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Early Telescopes Hevelius 140-ft Long Refractor
c. 1670
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Early Telescopes Huygens Aerial Telescope c.
1680
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Early Telescopes Hevelius Rooftop Observatory c.
1670
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Yerkes ObservatoryUniversity of Chicago,
Williams Bay, WI
40-inch (1-m) telescope is the worlds largest
refractor
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Mount Wilson ObservatoryMt. Wilson, CA
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Mount Wilson Observatory100-inch Telescope
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Mount Wilson Observatory100-inch Dome with Orion
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Mount Wilson Observatory150-ft Solar Tower with
Comet Hale-Bopp 1997
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Mount Palomar ObservatoryCaltech, Mt. Palomar, CA
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Kitt Peak National ObservatoryNational Science
Foundation, Kitt Peak, AZ
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Kitt Peak National Observatory4-m Mayall
Telescope
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Kitt Peak National Observatory4-m Mayall
Telescope Control Room
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Kitt Peak National ObservatoryMcMath-Pierce
Solar Telescopes
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Kitt Peak National ObservatoryWIYN Telescope
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Cerro Tololo Inter-American Observatory4-m
Telescope at Night
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Mauna Kea ObservatoryOn the Big Island of Hawaii
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W.M. Keck ObservatoryTwo 10-meter telescopes on
Mauna Kea
10-meters is the largest aperture of any single
telescope in the world.
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W.M. Keck ObservatoryWith NASA Sponsored
Interferometer Outriggers
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Gemini TelescopesTwo 8-meter telescopes on Mauna
Kea, Hawaii and Cerro Pachon, Chile
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European Very Large Telescope (VLT)Four
8.2-meter telescopes on Cerro Paranal, Chile
(latitude 25oS)
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Radio Telescopes And Interferometric Arrays
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The Green Bank Telescope (GBT)100-m Dish is
the Worlds Largest Fully Steerable Radio
Telescope
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Arecibo Radio Telescope 1000-ft Radio/Radar
Telescope in Arecibo, PR
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The Very Large Array (VLA)National Radio
Astronomy Observatory, near Socorro, NM
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The Very Long Baseline Array (VLBA)National
Radio Astronomy Observatory
Kitt Peak Site
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Telescopes in Space
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NASAs Great Observatories
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Hubble Space Telescope
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James Webb Space Telescope To be launched in 2013
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James Webb Space Telescope On display in Orlando,
June 2006
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Georgia State Universitys 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
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GSUs Hard Labor Creek Observatory Rutledge, GA
Multiple-Telescope Telescope
16-in Cassegrain Telescope
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Optical Interferometry
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GSUs CHARA Array Mt. Wilson, CA
E1
E2
W1
OPLE
W2 (Keck)
100-in
BCL
Michelson Building
S2
60-in
Kapteyn Cottage
S1
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CHARAs Telescope Enclosures
Concept Engineering by Sea West Enterprises,
Inc.
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Installing CHARAs Telescope Enclosures February
1998
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CHARAs 1-meter Telescopes
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CHARAs Beam Synthesis Facility

• 308-ft long, 12,000 ft2 area
• A Building within a Building
• Thermally Vibrationally Stabilized
• Encloses OPLEs BCL

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Optical Delay Lines
South Cart Pair
JPL Integration
Setting Sleepers
Metrology Laser
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GSUs CHARA Array Mt. Wilson, CA