Today! From Earth’s Perspective: A. Celestial Coordinates B. Precession of the equinoxes C. Astrology? The Celestial Sphere (Pythagoras) FROM NOTES Celestial sphere--imaginary sphere on which the 'fixed stars' are located --gives angular position of objects in the sky, has arbitrary size, and earth turns underneath it. Zenith--point directly overhead on sphere. Local Coordinates—altitude and azimuth. Celestial poles--points just above N. and S. pole. Meridian--circle passing through poles and zenith. A great circle--divides sphere in half. A Great Circle (the meridian is an example) on the sphere has 360 degrees. 1 degree = 60 (arc)minutes = 60' 1 (arc)minute= 60 (arc)seconds = 60" Celestial equator--great circle on the sphere formed by cutting through earth's equator. The ecliptic--great circle which is sun's path --tilted 23 ½E from the celestial equator. Angular separation (distance)--no. of deg., min., sec. between objects or points on sphere. Angular size or diameter--angle an object subtends at observer's distance. Local Coordinates: altitude and azimuth Dobsonian telescope: moves in local coordinates On the celestial sphere, stars are like cities on the sky. Just like cities on the earth, it takes two coordinates To give us their location. The two ‘Celestial Coordinates’ on the Celestial Sphere are analogous to longitude and latitude. Right Ascension—0-24 hours (like time zones, but on the sky). Starts at star Psi Piscium, present position of the Vernal Equinox, point where the Sun crosses the celestial equator. Declination—0 to + or – 90 degrees (Latitude is N. and S.) Precession of the Equinoxes--earth's axis traces out a circle on the sky every 25,800 years, and the point of the vernal equinox shifts through all the signs of the zodiac. Polaris will Not always be The North Celestial Pole. Earth’s axis points toward 12 signs in succession. Also the sun, seen from earth, moves around in 1 year. Zodiac--the circular band of 12 constellations the sun passes in front of, one cycle in a year. Called the 'circle of animals'--the 12 astrological signs. Claudius Ptolemy wrote a book called Tetrabiblios around 150 AD. This codified Western Astrology. However, the Precession of the Equinoxes has changed the position of the sun in the zodiac by about two thirds of a sign since Ptolemy. Those born between about the 22nd of each month Through the 10th of the next Actually had the previous sign at birth. In the 1970’s, Michel Guaquelin, a psychologist With an open mind, studied 60,000 birth charts With an open mind and scientific statistics. He found no evidence for: Sun signs Houses Aspects But he did find evidence that: Mars and other planets being at power points (just above the horizon, or just below —and at right angles–at birth) relate to success in sports and other occupations. It does also seem that planets in these positions impart the planetary influences indicated by astrologers.