1. Constellations

2. Celestial Sphere

3. Our Point of View

4. Angular Size and Distance

5. Relevant Geography

6. Earth’s Rotation 23 hours and 56 minutes relative to background stars (sidereal period) Spin axis of Earth defines points on the celestial sphere (using north and south poles) –North Celestial Pole –South Celestial Pole –Celestial Equator Sky appears to rotate east to west about the celestial poles because Earth rotates west to east.

7. Celestial Sphere

8. Motion on the Sky

9. Motion Depends on Declination

10. Circumpolar Constellations Circumpolar constellations never set. Circumpolar constellations change with latitude… sky changes with latitude

11. Tilt of Spin Axis

12. The Ecliptic

13. Ecliptic on the Celestial Sphere

14. The Equinoxes and Solstices Tilt of the spin axis is related to the seasons Effect of tilt on climate is not instantaneous

15. Precession of the Earth’s Axis

16. North Celestial Pole Changes