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Telescopes

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Telescopes

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  1. Telescopes

  2. Telescope History • Galileo Galilei built first refractive telescope in 1609 • Isaac Newton built the first reflective telescope in 1668

  3. 1st Reflecting Telescope by Isaac Newton

  4. Optical Telescopes • Telescopes that contain mirrors, lenses, or both • Three properties: • Light-gathering power • Resolving power • Magnifying power

  5. 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

  6. Refracting Telescopes • Telescope uses two lens to bend or refract light • Simplest of all telescopes • First refracting telescope capable of magnifying objects 30 times.

  7. 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

  8. Eyepiece Lens • The second lens used in a refractive telescope • Eyepiece magnifies image produced by the objective lens

  9. Simple Refracting Telescope

  10. 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

  11. Yerkes ObservatoryLargest Refracting Telescope

  12. Yerkes ObservatoryWilliams Bay, Wisconsin

  13. Refracting Telescope at Lick ObservatorySouthern California

  14. Lick Observatory

  15. 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

  16. Reflecting Telescope

  17. 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.

  18. Mount Palomar ObservatoryCalifornia

  19. Mirror for Hale Telescope at Mount Palomar Observatory

  20. Hale Telescope

  21. Keck TelescopesWorld’s Largest Reflecting Telescopes Hawaii

  22. Schematic of KeckMultiple Mirros Telescope (MMT)

  23. Kitt Peak ObservatoryArizona

  24. La Palma ObservatoryCanary Islands, Spain

  25. McDonald ObservatoryTexas

  26. Cerro Tololo ObservatoryChile

  27. 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!

  28. Radio Telescopes • These big dishes are used to detect radio waves • Focuses incoming radio waves on an antenna and transmits these to an amplifier.

  29. Radio Signals • Radio signals are weak so it requires a very large dish • These telescopes have poor resolution • Radio Interferometer= Wire several telescopes together

  30. 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

  31. Disadvantages • Can be affected by human-made radio interference • Usually placed in valleys to block interference

  32. Largest Radio Telescope in WorldArecibo, Puerto Rico

  33. VLA Radio TelescopeSocorro, New Mexico

  34. VLA

  35. Space Telescopes • Orbit above Earth’s atmosphere and produce clearer images

  36. 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

  37. www.hubblesite.org

  38. 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