1. Sky Motions  Diurnal Motion Annual Motion

2. DIURNAL MOTION o Daily East / West motion of the sky Due to the Earth’s rotation (15°/hour) [360°/24 hours = 15°/hour] [1° in 4 minutes] o Stars fall into two groups Circumpolar - never rise or set Equatorial

3. Circumpolar Stars

4. Equatorial Stars

5. View from the North Pole

6. View from the Equator

7. Coordinate System Coordinate System

8. Celestial Meridian Circle going through north and south points on the horizon and the zenith Z

9. Celestial Meridian Objects on the Meridian are at their highest point in the sky (transit) Objects on the Meridian are at their highest point in the sky (transit) Astronomical noon is when Sun is on the Meridian. Astronomical noon is when Sun is on the Meridian.  Does not mean the Sun is directly overhead.  Midnight is when the Sun is on the Meridian below the horizon.

10. Zenith This is a measure of how high above the horizon the star or planet is located. A star on the horizon has an altitude of 0 o while a star directly overhead (this point is called the z http://astro.unl.edu/naap/motion2/s tarpaths.html enith) has an altitude of 90 o.

11. What is the altitude of a star that is exactly halfway between the horizon and the zenith?

12. Polaris and Altitude Polaris “north star” Polaris “north star”  1 degee from NCP Altitude of polaris is always equal to the latitude of the observer. Altitude of polaris is always equal to the latitude of the observer.  Equator 0º altitude = 0º  North pole 90º altitude= 90º aka  Grosse pointe 42º altitude = 42º Zenith

13. South pole Can you see polaris? Can you see polaris?  Nope!

14. Annual Motion

15. ANNUAL MOTION- Earth’s revolution o Constellations move westward during the year.  Due to Earth’s orbital motion around the Sun  Sun appears to moves eastward 1°/day Path of the Sun called the ECLIPTIC Path of the Sun called the ECLIPTIC o Ecliptic inclined 23.5° to Equator  Horizon calendar

16. Horizon Calendar

17. S N W E Polaris On the day of an equinox… On the day of an winter solstice… On the day of an summer solstice… The Sky DomeSunrises and Sunsets

18. S N W E Polaris Vernal or Autumnal Equinox Summer Solstice Winter Solstice Starting Points for the Sun

19. Sunrise in Athens

20. Stonehenge

21. Earth’s Annual Motion Leo

22. Celestial Sphere Celestial Equator SCP NCP Ecliptic Vernal Equinox Autumnal Equinox 23.5°

23. Sun’s Motion Tool

24. Inclined Pole causes Seasons 23.5° Northern Hemisphere Summer Northern Hemisphere Winter N S

25. Sun’s motion along the Ecliptic Sun’s Motion

26. Annual Motion Affects the Nighttime Sky Day 1 9:00 PM

27. Annual Motion Affects the Nighttime Sky Day 2 8:56 PM

28. Annual Motion Affects the Nighttime Sky Day 3 8:52 PM

29. Annual Motion Affects the Nighttime Sky One Year Later 9:00 PM

30. “Stars” o Fixed Stars  Modern concept of stars  Form the Constellations o Planets - traveling or wandering stars  Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn o Meteors - “shooting stars” o Comets - “long-haired stars”

31. Babylonian Astronomy

32. Star Charts

33. Babylonian Astronomy Fatalistic Pre-determinism Everything in nature pre-determined by the gods Doesn’t lend itself to model building Infinite time line

34. End of Section