1. Charles Hakes Fort Lewis College1

2. Charles Hakes Fort Lewis College2 Chapter 3 Telescopes The Tools of Astronomy

3. Charles Hakes Fort Lewis College3 Charles Hakes Fort Lewis College3 Hotel Mauna Kea l http://www.youtube.com/watch?v=XPdTlHK1h_0 http://www.youtube.com/watch?v=XPdTlHK1h_0

4. Charles Hakes Fort Lewis College4 Outline Test Friday Don’t forget your green/red scantron sheets #2 pencil(s). Calculator (no phone calculators) Optical Telescopes Refractors Reflectors Others Other Wavelengths

5. Charles Hakes Fort Lewis College5 Drop-in Study Sessions Thursday 2:30-4:30 Use it or lose it. Don’t forget conversion practice page Review questions on-line also

6. Charles Hakes Fort Lewis College6 Review What was the most important thing you learned? the speed of light, x-ray, gamma rays... is all the same. (~= 3.00x10 8 m/s) wavelength x frequency = velocity frequency = 1/period Electromagnetic waves don’t need anything to move in. There are far more types of invisible “light” than there are visible

7. Charles Hakes Fort Lewis College7 Charles Hakes Fort Lewis College7 The Speed of Light 299,792.458 km/sec (~= 3.00x10 8 m/s) It’s not just a good idea. It’s the law!

8. Charles Hakes Fort Lewis College8 Charles Hakes Fort Lewis College8 History of The Speed of Light

9. Charles Hakes Fort Lewis College9 Charles Hakes Fort Lewis College9 Figure 2.4 Charged Particles

10. Charles Hakes Fort Lewis College10 Charles Hakes Fort Lewis College10 Figure 2.5 Magnetism

11. Charles Hakes Fort Lewis College11 Charles Hakes Fort Lewis College11 Figure 2.6 Electromagnetic Wave

12. Charles Hakes Fort Lewis College12 Charles Hakes Fort Lewis College12 Figure 2.7 Visible Spectrum

13. Charles Hakes Fort Lewis College13 Charles Hakes Fort Lewis College13 Figure 2.8 Electromagnetic Spectrum

14. Charles Hakes Fort Lewis College14 Which is correct A) period * frequency = wavelength B) velocity / period = wavelength C) velocity * frequency = wavelength D) velocity * period = wavelength

15. Charles Hakes Fort Lewis College15 Which is correct A) period * frequency = wavelength B) velocity / period = wavelength C) velocity * frequency = wavelength D) velocity * period = wavelength

16. Charles Hakes Fort Lewis College16 Which list is in the correct order of electromagnetic radiation frequency, going from lowest to highest? A) infrared, ultraviolet, gamma, radio B) gamma, x-ray, ultraviolet, visible C) radio, infrared, visible, ultraviolet D) radio, x-ray, ultraviolet, visible E) red, violet, blue, green

17. Charles Hakes Fort Lewis College17 Which list is in the correct order of electromagnetic radiation frequency, going from lowest to highest? A) infrared, ultraviolet, gamma, radio B) gamma, x-ray, ultraviolet, visible C) radio, infrared, visible, ultraviolet D) radio, x-ray, ultraviolet, visible E) red, violet, blue, green

18. Charles Hakes Fort Lewis College18 Discussion/Exercise What is the wavelength of a microwave oven at 2.45 GHz?

19. Charles Hakes Fort Lewis College19 What is the wavelength of a microwave oven at 2.45 GHz? A) 7.35x10 17 m B) 0.735 m C) 122 m D) 0.122 m

20. Charles Hakes Fort Lewis College20 Chapter 3 Hubble Space Telescope and VLT

21. Charles Hakes Fort Lewis College21 Figure 3.6bc Palomar Telescope

22. Charles Hakes Fort Lewis College22 Figure 3.8 Mauna Kea Observatory

23. Charles Hakes Fort Lewis College23 Figure 3.9 VLT Observatory

24. Charles Hakes Fort Lewis College24 Figure 3.X FLC Observatory

25. Charles Hakes Fort Lewis College25 Figure 3.X FLC Observatory

26. Charles Hakes Fort Lewis College26 Telescopes What is a telescope? What does it do for you?

27. Charles Hakes Fort Lewis College27 Telescopes A telescope is a “light bucket” - it gathers photons. A telescope is an imaging device - it focuses the photons. It also magnifies, but this is less important.

28. Charles Hakes Fort Lewis College28 Figure 3.1 Reflecting Mirror

29. Charles Hakes Fort Lewis College29 Figure 3.3 Image Formation

30. Charles Hakes Fort Lewis College30 Types of Telescopes Refractor Galilean Achromatic Apochromatic Reflector Newtonian Cassegrain Catadioptric Schmidt Cassegrain Maksutov Cassegrain

31. Charles Hakes Fort Lewis College31 Figure 3.4 Reflectors and Refractors

32. Charles Hakes Fort Lewis College32 Refractors

33. Charles Hakes Fort Lewis College33 Figure 3.2 Refracting Lens

34. Charles Hakes Fort Lewis College34 Figure 2.7 Visible Spectrum

35. Charles Hakes Fort Lewis College35 Refractors Galilean - Uses one positive and one negative lens. No longer made. (except for toys = “pirate” telescope) Very narrow field of view Achromatic Apochromatic

36. Charles Hakes Fort Lewis College36 Refractors Achromatic Most common type of small telescope today. The “objective” lens has two different types of glass. Red light and green light can focus in the same spot. Often have a “purple haze” on bright objects. Apochromatic Uses exotic glass or more than two lens elements. Gets three of more colors to focus together - no more purple haze Expensive.

37. Charles Hakes Fort Lewis College37 Demonstration Making a refractor telescope Objective Eyepiece Mount

38. Charles Hakes Fort Lewis College38 Reflectors Newtonian Parabolic mirror Several places possible to focus the light.

39. Charles Hakes Fort Lewis College39 Figure 3.5 Reflecting Telescopes

40. Charles Hakes Fort Lewis College40 Reflectors Assembly Demonstration Advantages can make mirrors bigger (can support them from the back) Reflection only on surface (colors focus together) Only need one optical surface (lenses require at least two)

41. Charles Hakes Fort Lewis College41 Telescopes Building your own telescope can be very fun and rewarding. You cannot build a telescope as cheaply as you can buy one. Be sure to get good eyepieces. Half the imaging device is the eyepiece. Some can be expensive, however.

42. Charles Hakes Fort Lewis College42 Telescopes No telescope is good at all things. Know what you want to observe. The best telescope is the one that gets used the most.

43. Charles Hakes Fort Lewis College43 Useful Parameters Focal ratio (focal length/diameter) Magnification (FL/fl) maximum 50x/inch rule of thumb or… 300x max (from the atmosphere) Exit pupil (diameter/magnification) 7mm max 0.5mm min

44. Charles Hakes Fort Lewis College44 Figure 3.7 Sensitivity Size does matter Bigger is better! (diameter, that is)

45. Charles Hakes Fort Lewis College45 Figure 3.6a Palomar Telescope

46. Charles Hakes Fort Lewis College46 Figure 3.6bc Palomar Telescope

47. Charles Hakes Fort Lewis College47 Figure 3.8 Mauna Kea Observatory

48. Charles Hakes Fort Lewis College48 Figure 3.9 VLT Observatory

49. Charles Hakes Fort Lewis College49 Telescope size Light gathering ability is proportional to the area of the objective. This means it is proportional to the diameter squared. 8” telescope gathers 4 times the light of a 4” telescope. ( 8”x8”=64 sq in, 4”x4”=16 sq in ) Photographic exposures would be 1/4 as long on the 8” as they would be on the 4” Similarly, an 8” telescope gathers 1/4 as much light as a 16” telescope.

50. Charles Hakes Fort Lewis College50 Size Example - Binoculars 10x50 binoculars “10” means - “50” means - How much more light can they gather than your naked eye? eyes ~7mm diameter

51. Charles Hakes Fort Lewis College51 Size Example - Binoculars 10x50 binoculars “10” means - magnification “50” means - How much more light can they gather than your naked eye? eyes ~7mm diameter

52. Charles Hakes Fort Lewis College52 Size Example - Binoculars 10x50 binoculars “10” means - magnification “50” means - diameter in mm How much more light can they gather than your naked eye? eyes ~7mm diameter

53. Charles Hakes Fort Lewis College53 Size Example - Binoculars 10x50 binoculars ~50x area of pupil. To get another 50x light gathering power, you would need ~14” diameter telescope!

54. Charles Hakes Fort Lewis College54 A 5 meter (diameter) telescope A) gathers 5 times as much light as a 1 m telescope B) gathers 1/2 as much light as a 10 m telescope C) gathers 4 times as much light as a 2.5 m telescope D) gathers 5/2 as much light as a 2 m telescope

55. Charles Hakes Fort Lewis College55 A 2 meter telescope takes a picture of a galaxy in 10 minutes. How long will it take to make the same exposure using a 1 meter telescope? A) 5 minutes B) 2.5 minutes C) 20 minutes D) 40 minutes

56. Charles Hakes Fort Lewis College56 Figure 3.10 Resolution

57. Charles Hakes Fort Lewis College57 Three Minute Paper Write 1-3 sentences. What was the most important thing you learned today? What questions do you still have about today’s topics?