Download - Telescopes
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Telescopes
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Telescope History
Galileo Galilei built first refractive telescope in 1609
Isaac Newton built the first reflective telescope in 1668
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1st Reflecting Telescope by Isaac Newton
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Optical Telescopes
Telescopes that contain mirrors, lenses, or both
Three properties:• Light-gathering power• Resolving power• Magnifying power
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Optical Telescopes
Telescopes with larger mirrors/lenses:• Can“see”farther into space• Have greater resolution
Magnification can be changed by using different eyepieces
Usually placed on mountain tops to reduce city lights
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Refracting Telescopes
Telescope uses two lens to bend or refract light
Simplest of all telescopes First refracting telescope capable of
magnifying objects 30 times.
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Objective Lens
Most important lens is the objective lens• Bends the light from a distant object and
focuses the light at the focus to produce an image
• The objective lens produces a very small, bright image of an object
Focus= central point Focal length= distance between the focus
and the objective lens
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Eyepiece Lens
The second lens used in a refractive telescope
Eyepiece magnifies image produced by the objective lens
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Simple Refracting Telescope
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Disadvantages
Shorter wavelengths of light are bent more than the longer ones
Chromatic aberration: • Weakens image and creates a halo of
color around it• When red light is in focus, a bluish halo
appears. Very hard to produce a large piece of
high-quality, bubble-free glass
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Yerkes ObservatoryLargest Refracting Telescope
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Yerkes ObservatoryWilliams Bay, Wisconsin
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Refracting Telescope at Lick ObservatorySouthern California
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Lick Observatory
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Reflecting Telescopes
Uses a concave (curved) mirror that focuses the light in front of it
Mirror is coated in a highly reflective material, an aluminum compound
Two mirrors- one large & concave and one small & flat
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Reflecting Telescope
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Advantages
No Chromatic aberration because reflected light is not dispersed into its component colors.
Glass does not need to be high-quality because light does not pass through it.
Disadvantage–secondary mirror blocks some light entering the telescope.
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Mount Palomar ObservatoryCalifornia
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Mirror for Hale Telescope at Mount Palomar Observatory
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Hale Telescope
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Keck TelescopesWorld’s Largest Reflecting Telescopes
Hawaii
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Schematic of KeckMultiple Mirros Telescope (MMT)
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Kitt Peak ObservatoryArizona
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La Palma ObservatoryCanary Islands, Spain
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McDonald ObservatoryTexas
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Cerro Tololo ObservatoryChile
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Invisible Light
Stars produce light wavelengths that are not visible to our eyes• Gamma rays, X-rays, ultraviolet
radiation, infrared radiation, and radio waves
• Most of these can not get past our atmosphere… so we must get our cameras above it!
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Radio Telescopes
These big dishes are used to detect radio waves
Focuses incoming radio waves on an antenna and transmits these to an amplifier.
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Radio Signals
Radio signals are weak so it requires a very large dish
These telescopes have poor resolution• Radio Interferometer= Wire several
telescopes together
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Advantages
Less affected by turbulence in the atmosphere, clouds, and weather
No protective dome is required = cheaper
Can be used and “viewed” 24 hours a day
Radio signals can pass through intersteller dust clouds
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Disadvantages
Can be affected by human-made radio interference• Usually placed in valleys to block
interference
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Largest Radio Telescope in WorldArecibo, Puerto Rico
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VLA Radio TelescopeSocorro, New Mexico
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VLA
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Space Telescopes
Orbit above Earth’s atmosphere and produce clearer images
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Hubble Space Telescope
Built by NASA and sent in April 1990 10 billion times more light-gathering
power than the human eye Given us amazing images of space
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Other Space Telescopes
Chandra X-Ray Observatory• NASA uses to study X-rays• Launched in 1999• Gather data about black holes
Compton Gamma-Ray Observatory• Used to study visible light and gamma rays
In 2018, NASA will launch James Webb Space Telescope to study infrared radiation• Run into many obstacles and budget problems