1. IAU – International Astronomical Union • Determined the 88 constellations • Remember the Celestial Sphere, spherical “shells”? • When viewing stars using the Horizon System, the coordinates reference where sky meets land. • You can coordinate stars Using Altitude and Azimuth Constellations ~ part dos

2. Azimuth begins on the horizon due North at Spring Equinox = 0ºand goes CLOCKWISE; 90º, 180º, 270º Azimuth

3. The angle of an object above the horizon. • Measured in degrees along a line perpendicular to the horizon. • An object on the horizon has an altitude of 0º • Zenith is the point directly overhead (90º up) • Nadir is directly below you on the other side of the world • The Meridian is an imaginary line which starts at Northern Azimuth 0º on the horizon up to Zenith 90º and over to the South 180º Altitude

4. Altitude and Azimuth

6. I know it is called Alt-azimuth Coordinates but when using altitude and azimuth to point out a celestial object you first specify the azimuth then the altitude! • You may use zenith instead of 90º • Of course every observer is different so alt-azimuth will vary. Since Earth rotates the alt-azimuth can ID celestial objects as a given time but is not sufficient for their permanent direction in space Alt-azimuth Coordinates

7. Stretching your thumb and pinkie out (shaka) when looking at the sky is about 25º • Closed fist is about 10º • 3 fingers is about 5º • pinkie is about 1º • Within 1º is 60 arc minutes • In 60 arc minutes is 60 arc seconds Describing angular distance