1. ASTR-1010 Planetary Astronomy Day - 18

2. Announcements Smartworks Chapters 4: Due Monday, March 1. Smartworks Chapter 5 is also posted Exam 2 will cover chapters 3, 4, & 5 -Target Wednesday, March 3

3. ClassAction Stuff Splash page questions

4. Telescopes & Instruments

5. Telescopes Telescopes have three functions: 1.Gather light LGP ∝ Area = πR 2 2.Resolve objects Θ = 2.06 X 10 5 ( λ/D) 3.Magnify EXTENDED objects

6. The light gathering power is proportional to the area

7. Properties of light: Refraction The Speed of Light is less in glass than in vacuum

8. Refraction through a plane of glass only shifts the light, a lens with curved surfaces focuses the light

9. The refracting telescope uses two lenses

10. Refractors suffer from Chromatic Aberration

11. Chromatic Aberration distorts colors Rainbows appear around bright white objects

12. ClassAction Stuff Simple Telescope Snell’s Law Splash page questions

13. Correcting for Chromatic aberration can be expensive

14. Large refractors can be very long and bulky. The largest has a 40” diameter

15. The Yerkes 40” moves the floor to view at low angles

16. Cheaper Way Mirrors

17. Reflection is the bouncing of light off a surface

18. A concave mirror focuses light

19. There are several types of reflecting telescopes

20. Spherical mirrors suffer from Spherical Aberration

21. Spherical aberration can be eliminated by a parabolic shape or a corrector plate

22. The Largest Optical Telescopes Keck I and II

23. The 10 meter Keck Mirror

24. The Hobby-Eberly Telescope

25. Coming “soon” The 30m Telescope

26. The resolution of a telescope depends on its size and the wavelength of the light

27. The atmosphere limits the resolving power of a ground- based telescope

28. Differences in the temperature and density of small portions of Earth’s atmosphere cause passing starlight to quickly change direction, making stars appear to twinkle.

29. Earth’s atmosphere hinders astronomical research Image of stars taken with a telescope on the Earth’s surface Same picture taken with Hubble Space Telescope high above Earth’s blurring atmosphere