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Solar Hour Angle

Solar Hour Angle for a particular location on the earth is zero when the sun is straight overhead, negative before local noon and positive in the afternoon.  In one 24 hour period, the Solar Hour Angle changes by 360 degrees (i.e. one revolution).

Solar Hour Angle in Degrees True Solar Time
... ...
-90 6 hours before Solar Noon
-75 5 hours before Solar Noon
-60 4 hours before Solar Noon
-45 3 hours before Solar Noon
-30 2 hours before Solar Noon
-15 1 hour before Solar Noon
0 Sun overhead i.e. Solar Noon
15 1 hour after Solar Noon
30 2 hours after Solar Noon
45 3 hours after Solar Noon
60 4 hours after Solar Noon
75 5 hours after Solar Noon
90 6 hours after Solar Noon
... ...

 

Coordinate System

The Hour Angle is a measure in an equatorial coordinate system.  The Equatorial Coordinate system uses the world itself as it's axes.  The centre of the earth is the origin.  The other coordinate in this system is Declination

Calculate it!

The Sun API provides the sdxH function to calculate the Solar Hour Angle.