Altitude and Azimuth (Alt/Az) coordinates tell you where to look for an object in the sky.  These coordinates are taken from an observer's Latitude and Longitude position.  

     The point in the sky that's straight up over your head is called zenith.  This point has an Altitude of +90 degrees.  The point straight down is called nadir.  It has an Altitude of -90 degrees.  The horizon has an Altitude of 0 degrees.  If you look at an object that's half way from the horizon to zenith, it would have an Altitude of 45 degrees.  Any Altitude coordinate that begins with a minus is below the horizon and is not able to be seen.  Now you know that Altitude means how far up from the horizon to look.

     Azimuth tells you which direction to look.  An Azimuth of 0 degrees tells you to look north.  An Azimuth of 90 degrees tells you to look east.  An Azimuth of 180 degrees tells you to look south.  An Azimuth of 270 degrees tells you to look west.

     Now you can read Alt/Az coordinates.

     Example: If an object's coordinates are at Altitude 30 degrees and Azimuth 190 degrees, you would look a little west of due south, a third of the way from the horizon to zenith.