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No-Name Clickers

No-Name Clickers. 4D8AC7 641AFE8 A9EDE4A DE3856B DEAEB0C E019A95 E103D23 E1C0E1C EEB8560 161E040C 1E0AF2E6 2304FED9 23210E0C 246EB0FA 24A429A9 24DAC53B 24E06FAB 25A321A7. Chapter 3 Telescopes. Telescopes. Optical Telescopes.

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No-Name Clickers

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  1. No-Name Clickers 4D8AC7 641AFE8 A9EDE4A DE3856B DEAEB0C E019A95 E103D23 E1C0E1C EEB8560 161E040C 1E0AF2E6 2304FED9 23210E0C 246EB0FA 24A429A9 24DAC53B 24E06FAB 25A321A7

  2. Chapter 3 Telescopes

  3. Telescopes

  4. Optical Telescopes Images can be formed through reflection or refraction. Reflecting mirror Collect a large amount of light

  5. Optical Telescopes Refracting lens

  6. Optical Telescopes Reflecting and refracting telescopes

  7. Optical Telescopes • Modern telescopes are all reflectors: • Light traveling through lens is refracted differently depending on wavelength. • Some light traveling through lens is absorbed. • Large lens can be very heavy, and can only be supported at edge. • Lens needs two optically acceptable surfaces, mirror only needs one.

  8. Chromatic aberration

  9. Question 1 a)light passing through lenses can be absorbed or scattered. b)large lenses can be very heavy. c)large lenses are more difficult to make. d)mirrors can be computer controlled to improve resolution. e)reflecting telescopes aren’t affected by the atmosphere as much. Modern telescopes use mirrors rather than lenses for all of these reasons EXCEPT

  10. Question 1 a)light passing through lenses can be absorbed or scattered. b)large lenses can be very heavy. c)large lenses are more difficult to make. d)mirrors can be computer controlled to improve resolution. e)reflecting telescopes aren’t affected by the atmosphere as much. Modern telescopes use mirrors rather than lenses for all of these reasons EXCEPT Reflecting instruments like the KECK telescopes can be made larger, and more capable, than refractors.

  11. Optical Telescopes Image acquisition: Charge-coupled devices (CCDs) are electronic devices, can be quickly read out and reset.

  12. CCD Camera Sensor

  13. Question 2 a) they don’t require chemical development. b) digital data is easily stored & transmitted. c) CCDs are more light sensitive than film. d) CCD images can be developed faster. e) All of the above are true. An advantage of CCDs over photographic film is

  14. Question 2 a) they don’t require chemical development. b) digital data is easily stored & transmitted. c) CCDs are more light sensitive than film. d) CCD images can be developed faster. e) All of the above are true. An advantage of CCDs over photographic film is

  15. Optical Telescopes Image processing by computers can sharpen images.

  16. Ground Based Telescope

  17. Early HST

  18. Computer Enhanced HST

  19. Later HST

  20. The Hubble Space Telescope The Hubble Space Telescope has several instruments.

  21. The Hubble Space Telescope Resolution achievable by the Hubble Space Telescope limited by optics and not atmosphere Ground Based – M100

  22. Telescope Size Light-gathering power: Improves detail Brightness proportional to square of radius of mirror The figure, part (b) was taken with a telescope twice the size of (a) R=1 Area = p R2 R=2

  23. Telescope Size Multiple telescopes: Mauna Kea

  24. Telescope Size The VLT (Very Large Telescope), Atacama, Chile

  25. Question 3 a) bend around corners and edges. b) separate into its component colors. c) bend through a lens. d) disperse within a prism. e) reflect off a mirror. Diffraction is the tendency of light to

  26. Question 3 a) bend around corners and edges. b) separate into its component colors. c) bend through a lens. d) disperse within a prism. e) reflect off a mirror. Diffraction is the tendency of light to Diffraction affects all telescopes and limits the sharpness of all images.

  27. Telescope Size Resolving power: Ability to distinguish objects that are close together. Resolution is proportional to wavelength and inversely proportional to telescope size.

  28. Question 4 a) larger telescopes & longer wavelengths. b) infrared light. c)larger telescopes & shorter wavelengths. d)lower frequency light. e)visible light. Resolution is improved by using

  29. Question 4 a) larger telescopes & longer wavelengths. b) infrared light. c)larger telescopes & shorter wavelengths. d)lower frequency light. e)visible light. Resolution is improved by using 10’ 1” Diffraction limits resolution; larger telescopes and shorter-wave light produces sharper images.

  30. Telescope Size Effect of improving resolution: (a) 10′; (b) 1′; (c) 5″; (d) 1″

  31. Question 5 a) the quality of the telescope’s optics. b) the transparency of a telescope’s lens. c) the sharpness of vision of your eyes. d) the image quality due to air stability. e) the sky’s clarity & absence of clouds. Seeing in astronomy is a measurement of

  32. Smeared overall image of star Point images of a star Question 5 a) the quality of the telescope’s optics. b) the transparency of a telescope’s lens. c) the sharpness of vision of your eyes. d) the image quality due to air stability. e) the sky’s clarity & absence of clouds. Seeing in astronomy is a measurement of “Good Seeing” occurs when the atmosphere is clear and the air is still. Turbulent air produces “poor seeing,” and fuzzier images.

  33. Question 6 a) making telescopes larger or smaller. b) reducing atmospheric blurring using computer control. c) collecting different kinds of light with one type of telescope. d) using multiple linked telescopes. Adaptive optics refers to

  34. Question 6 a) making telescopes larger or smaller. b) reducing atmospheric blurring using computer control. c) collecting different kinds of light with one type of telescope. d) using multiple linked telescopes. Adaptive optics refers to Cluster R136 Shaping a mirror in “real time” can dramatically improve resolution.

  35. High-Resolution Astronomy Atmospheric blurring due to air movements

  36. High-Resolution Astronomy • Solutions: • Put telescopes on mountaintops, especially in deserts. • Put telescopes in space. • Active (adaptive) optics – control mirrors based on temperature and orientation.

  37. High-Resolution Astronomy • Solutions: • Without active (adaptive) optics a 1m telescope is limited to about 2’ • With active (adaptive) optics the same 1m telescope could approach 0.1”.

  38. Radio Astronomy • Radio telescopes: • Similar to optical reflecting telescopes • Prime focus • Less sensitive to imperfections (due to longer wavelength); can be made very large 105 m Green Bank, WV

  39. Question 7 radio photons don’t carry much energy. they are painted white. c) they are cheap to make. d) they are can operate during the day. Radio dishes are large because

  40. Question 7 radio photons don’t carry much energy. they are painted white. c) they are cheap to make. d) they are can operate during the day. Radio dishes are large in order to Resolution is worse with long-wave light, so radio telescopes must be large to compensate.

  41. Radio Astronomy Largest radio telescope: 300-m dish at Arecibo

  42. Question 8 a)observations can be made day & night. b)we can see objects that don’t emit visible light. c)radio waves are not blocked by interstellar dust. d)they can be linked to form interferometers. e)All of the above are true. Radio telescopes are useful because

  43. Question 8 a)observations can be made day & night. b)we can see objects that don’t emit visible light. c)radio waves are not blocked by interstellar dust. d)they can be linked to form interferometers. e)All of the above are true. Radio telescopes are useful because The Very Large Array links separate radio telescopes to create much better resolution.

  44. Radio Astronomy • Longer wavelength means poorer angular resolution. • Advantages of radio astronomy: • Can observe 24 hours a day. • Clouds, rain, and snow don’t interfere. • Observations at an entirely different frequency; get totally different information. Centaurus A

  45. Radio Astronomy • Interferometry: • Combines information from several widely spread radio telescopes as if it came from a single dish. • Resolution will be that of dish whose diameter = largest separation between dishes.

  46. Radio Astronomy Interferometry requires preserving the phase relationship between waves over the distance between individual telescopes.

  47. Radio Astronomy Can get radio images whose resolution is close to optical. M51 4 m Kitt Peak VLA

  48. Radio Astronomy Interferometry can also be done with visible light, but much harder due to shorter wavelengths. CHARA 1 m at Mount Wilson, CA

  49. Other Astronomies Infrared radiation can image where visible radiation is blocked; generally can use optical telescope mirrors and lenses. Orion Nebula

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