Telescopes. Telescope History Galileo Galilei built first refractive telescope in 1609 Isaac...
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Transcript of Telescopes. Telescope History Galileo Galilei built first refractive telescope in 1609 Isaac...
Telescopes
Telescope History
Galileo Galilei built first refractive telescope in 1609
Isaac Newton built the first reflective telescope in 1668
1st Reflecting Telescope by Isaac Newton
Optical Telescopes
Telescopes that contain mirrors, lenses, or both
Three properties:• Light-gathering power• Resolving power• Magnifying power
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
Refracting Telescopes
Telescope uses two lens to bend or refract light
Simplest of all telescopes First refracting telescope capable of
magnifying objects 30 times.
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
Eyepiece Lens
The second lens used in a refractive telescope
Eyepiece magnifies image produced by the objective lens
Simple Refracting Telescope
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
Yerkes ObservatoryLargest Refracting Telescope
Yerkes ObservatoryWilliams Bay, Wisconsin
Refracting Telescope at Lick ObservatorySouthern California
Lick Observatory
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
Reflecting Telescope
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.
Mount Palomar ObservatoryCalifornia
Mirror for Hale Telescope at Mount Palomar Observatory
Hale Telescope
Keck TelescopesWorld’s Largest Reflecting Telescopes
Hawaii
Schematic of KeckMultiple Mirros Telescope (MMT)
Kitt Peak ObservatoryArizona
La Palma ObservatoryCanary Islands, Spain
McDonald ObservatoryTexas
Cerro Tololo ObservatoryChile
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!
Radio Telescopes
These big dishes are used to detect radio waves
Focuses incoming radio waves on an antenna and transmits these to an amplifier.
Radio Signals
Radio signals are weak so it requires a very large dish
These telescopes have poor resolution• Radio Interferometer= Wire several
telescopes together
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
Disadvantages
Can be affected by human-made radio interference• Usually placed in valleys to block
interference
Largest Radio Telescope in WorldArecibo, Puerto Rico
VLA Radio TelescopeSocorro, New Mexico
VLA
Space Telescopes
Orbit above Earth’s atmosphere and produce clearer images
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
www.hubblesite.org
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