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 = 0 º and goes CLOCKWISE; 90 º, 180º, 270º 90 º, 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 0 º  Zenith is the point directly overhead (90 º up)  Nadir is directly below you on the other side of the world  The Meridian is an imaginary line which starts at Northern Azimuth 0 º on the horizon up to Zenith 90 º and over to the South 180 º 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 90 º  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 25 º  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 Describing angular distance