1. Telescopes

4. Doppler Effect
The frequency of electromagnet radiation depends on the relative motion of the observer and the source.

5. Water Waves

6. Discussion
If the leaf is moving toward the source of the water waves, will the frequency be greater or less than when the leaf was still?

9. Discussion
Which has higher frequency red light or blue light?

10. Doppler Shift with Light
If you are moving toward the source, light is shifted to higher frequencies, or toward the blue end of the spectrum. Astronomers
call is a blueshift.
Likewise if you are moving away from a source, the light is shifted toward the red end of the spectrum and is called a redshift.

11. Important points
A Doppler shift is not a change in color. You can have a red spectral line which is blueshifted, or a blue line which is redshifted.
The Doppler effect does not depend on distance, does depend on your relative velocity toward or away from an object.

12. Rest frame spectrum
Doppler shifted spectrum

13. Doppler shifted spectra

14. Important points
3. The Doppler effect can only measure the radial velocity, the velocity toward or away from a source. It does not depend on the velocity of the object across the plane of the sky.

16. Radar measurement of Mercury’s rotation

17. Discussion
If you had a Coke bottle and you wished to fill it with rainwater falling from the sky, how would you do it?

18. Telescopes Serve 3 Functions
To collect light
To resolve fine detail
To magnify the image

19. Discussion
Of the three telescope functions which do you think is the most important in astronomy and why?

20. Refractor

22. Refraction (Marching Band Analogy)
What happens to the marching band if it hits a muddy part which causes the individual band members to slow?

23. Refraction (Marching Band Analogy)

24. Refraction (Marching Band Analogy)

25. Refraction (Marching Band Analogy)

30. Speed of light in glass Light moves slower in glass than in a vacuum
Speed of light through glass is different for different frequencies and each frequency has a slightly different focus.

31. Chromatic aberration

32. Mirrors

33. Reflectors

35. Mt Palomar observing cage

36. Resolution
The ability to separate two closely spaced objects, such as a double star.
The bigger your telescope objective the better your resolution will be.

37. Resolution

38. Alcor and Mizar

39. Resolution and the atmosphere
Atmospheric turbulence limits the resolution of even the largest telescopes on Earth to about that of a 6 inch telescope.

40. Points of light
Stars are so far away that they appear as points of light no matter how big a telescope you observe them with.
Bigger stars in photographs are simply brighter.

42. “Seeing”
The apparent size of the stars as viewed through the telescope.
Good “seeing” is typically 1 arcsec.

43. Atmospheric distortion

44. Seeing

45. Atmospheric distortion

46. Discussion
What can astronomers do to try and improve resolution of their observations?

47. Hubble Space Telescope

48. Mauna Kea

49. Keck primary mirror

50. Adaptive optics
Actuators deform the primary mirror hundreds of times a second to try and remove atmospheric distortion.

54. Discussion
Adaptive optic telescopes work best in the infrared region of the spectrum and not in the visible. Why do you think that is?

57. Discussion
What do you think happens when very high energy gamma rays from space hit the Earth’s atmosphere?

59. Discussion
Why can’t the very long wavelength radio waves make it to Earth’s surface?

60. Atmospheric absorption