Lecture 2 – The Celestial Sphere and the local sky; Changes over Time
Summary / Checklist of the Main Concepts to Understand and Remember

Motions of the Earth  
• How do we know the Earth spins? How long does it take to spin once?  
red bullet How do we know the Earth moves around the Sun?  
red bullet What is the reason for the changing seasons on Earth? Why is it not a changing distance to the Sun?  
red bullet What are equinoxes and solstices, and when do they happen?  
Locating Astronomical Objects  
red bullet What is the Celestial Sphere? What are the Celestial North and South Poles, the Ecliptic and the Celestial Equator?  
• What are right ascension and declination? [In what units are they measured?]  
red bullet Locating objects in the local sky; The zenith, altitude and azimuth (or direction).  
red bullet Angular sizes of objects in the sky: Units and examples of the angular sizes of the Sun and Moon.  
Changes in the Sky over Time  
red bullet How does the position of celestial objects change through the night?  
red bullet How does the position of stars in the sky change from one day to the next?  
red bullet How long does it take stars to come back to the same position in the sky?  
red bullet How do the position of stars and of planets on the celestial sphere change over time?  
The Sky in August  
red bullet Some of the stars and constellations we talked about: Polaris, Sagittarius.  

Topics from the lecture page and textbook not listed above [or between square brackets] were not covered in class;
Underlined words indicate that I will expect students to remember a number or a name related to that topic.

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