1. Daily Motion

2. Local Sky
Depending on your location on earth you see completely different stars!
Some stars are always visible, they are circumpolar.

3. Local Sky (cont’d)
The local sky at 40 degrees latitude

4. Daily Rising and Setting
Due to the rotation of the Earth around its axis
Period of rotation: siderial day= 23h56m4.1s
1 solar day (Noon to Noon) =24h
Stars rotate around the North Star – Polaris
Why are these different?
Circumpolar – never rise or set 4

5. What time is it? Depends on where you are on the Earth!
Time zones ensure that the noon is really noon, i.e. sun is at highest point
To avoid confusion, use universal time (UT), the time at the meridian in Greenwich
UT = EST + 5 hrs
Daylight savings adds one hour in spring, so UT = EDT+ 4 hrs

6. The Time Zones
Established to insure that sun is at highest point approximately at noon in the middle of the time zone