ASTRON C10 Lecture Notes - Lecture 7: Deferent And Epicycle, Celestial Pole

• School: Berkeley
• Department: Astronomy
• Course: ASTRON C10
• Professor: Alexei Filippenko

Document Summary

Polaris - coincides very closely with the north celestial pole. Some stars are fixed to the celestial sphere. How long the star streak is can let you know how long the exposure is. The stars just travel in circular paths. When not on a pole or horizon, stars rise at an angle and set at an angle. 3 months later in march, you see it at 6 p. m. (when the sun sets) Stars rise earlier by 4 minutes each day. Season: a consequence of the tilt of the earth. In spring/summer, the sun passes closer to zenith. If the earth were to be tilted 90 then at least one side of the earth would be lit 24 hours. Planets are not embedded in the celestial sphere. In the outer sphere, there"s a fixed backdrop of stars embedded in the celestial sphere. It"s a natural but incorrect assumption that earth as the center of the universe.