For proper operation, the collectors must be oriented as close as possible to true
south. In most areas, this varies from the magnetic south given by a compass. A
simple correction must be made.
First, find the magnetic variation from an isogonic map. This is given in degrees
east or west from magnetic south. Use the map below if the site is in the continental
United States. Otherwise, a local map will show the magnetic variation.
lsogonic Map of the
For example, a site in Montana has a magnetic variation of 20 degrees east. This
means that true south is 20 degrees east of magnetic south. On a compass
oriented so the north needle is at 360 degrees, true south is in the direction
indicated by 160 degrees.
Magnetic Variation on