Date post: | 21-Dec-2015 |
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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.
Circumpolar Constellations
• Circumpolar constellations never set.
• Circumpolar constellations change with latitude… sky changes with latitude
The Equinoxes and Solstices
• Tilt of the spin axis is related to the seasons
• Effect of tilt on climate is not instantaneous