1. Observing Astronomy 315 Professor Lee Carkner Lecture 3

2. Our Point of View   Think about the motions of the heavens from different points of view  Remember that everything is moving at once

3. The Changing Sky  North Pole of the Earth is pointed at Polaris (the North or Pole star), which stays stationary as the other stars move around it   Caused by the rotation of the Earth on its axis   Caused by the motion of the Earth around the Sun

4. Diurnal Motion

5. Annual Motion

6. The Observer’s View

7. Observing  Can measure distance on the sky in degrees (360 degrees = complete circle)  Horizon --  Zenith --  Meridian --

8. Time and the Stars   Stars make one complete circuit around the sky in 24 hours   Example: if stars move 1/12 of the way around the sky, 2 hours have passed   Big Dipper is circumpolar (never sets)

9. The Solar Year

10. The Seasons   When the northern hemisphere is pointed at the Sun, it is summer here   Seasons are not caused by Earth being more or less distant from the Sun!!!

11. Direct and Indirect Sunlight

12. Solstice and Equinox  Solstice   When the Sun is highest or lowest in the sky  Equinox   When the Sun is overhead at the equator

13. Times of year  Vernal Equinox -- March  First day of spring   Summer Solstice -- June  First day of summer   Autumnal Equinox - -September   Day and night equal in length  Winter Solstice - December   Shortest day of the year

14. Changing Day Length

15. Lines on a Globe  Equator -- Sun is overhead at equinox  Tropic of Capricorn --  Tropic of Cancer --  Arctic and Antarctic Circles -- 23 1/2 degrees south or north of the pole, Sun never sets or rises at solstice time

16. Navigation  Latitude (degrees North of the Equator)    Longitude (degrees East or West of the Prime Meridian running through Greenwich England) 

17. The Celestial Sphere  Project the lines on a globe into space to form a coordinate system  North Celestial Pole --  Celestial Equator --

18. Celestial Coordinates  Right Ascension --  Declination --  The coordinates do not move or vary with location on the Earth, they are fixed to the stars

19. The Ecliptic   For observers the ecliptic is a line on the sky where the Sun, Moon and planets can be found 

20. Constellations of the Zodiac

21. Precession  The Earth “wobbles” as it spins, causing the Earth’s axis to point at different parts of the sky   This changes where the equinoxes are in the sky

22. Astrology  The belief that the positions of heavenly bodies at the time of your birth foretells your future    For example: March 8th = Pisces, but Sun is in Aquarius. All star signs are about 1 month off

23. Science and Pseudoscience   Astrology is a pseudoscience, it uses some of the terminology of science, but its basic tenets are not subject to proof 

24. Next Time  Meet back in Science 102  Read Chapter 3.1-3.4