Key Concepts:

1. How did Astronomy begin?
2. What is the celestial sphere?
3. How does it relate to your location and time?
4. What are the coordinate systems astronomers use?
5. What are constellations?

Prehistoric Astronomy

• curiosity
• time keepers: seasons, climates (e.g., Chomsungdae)
• navigation (The History of the Sextant)
• The sky is not constant, however, because of proper motion and precession of the Earth rotation axis

Celestial Sphere

• An imaginary sphere of the sky where all celestial bodies are projected against


• A geocentric concept


• It is not physical -- rather a model of the heavens


• Celestial Coordinates:
• Declination and Latitude (where is north or the North Star?)
• Right Ascension and Longitude
• Ecliptic: the Sun's apparent annual path among the constellations (the zodiac)

Horizontal Coordinate System Quiz 2a: What's my latitude? Quiz 2b: Length of a day

Constellations

• patterns stars form on the celestial sphere


• human desire:
• to seek order (or to identify patterns);
• to create and to imagine;


• practical uses:
• a mnemonic tool - e.g. navigation
• identification of regions on the celestial sphere
• historic constellations and star groupings


• Seasonal constellations


• 88 Constellations


• Google Sky (also check out Hubble Site gSky)


• Remember: proper motion and precession of the Earth rotation axis!!!

NEXT READING ASSIGNMENT: Units 6 & 7 (Schneider & Arny)