Difference between Magnetic South & Solar South?

BilljustBill Solar Expert Posts: 219 ✭✭✭
As a beginner, do I understand that Magnetic South and Solar South are not the same thing?

Finding the Magnetic South using a military compass, it appears the South roof site I have is facing about 7 or 8 degrees East of the compass needle.

Using one of the online Angle calculators, I get this:
Latitude: 32.761992
Longitude: -97.688549

In the whole scheme of things, 8 degrees may not mean much for an Off Grid 1kw fixed roof array. Although, not knowing Solar South might mean that it's actually 14-16 degrees Longitude off on the 22-1/2* roof pitch. Then, as I plan for installation of the fixed array, I would have to angle the panels as well as tilt them for the best Winter production....

If you know the Magnetic South, how do you know where the Solar South is?




  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    Re: Difference between Magnetic South & Solar South?

    This might help http://www.builditsolar.com/SiteSurvey/FindingSouth.htm Hope this helps???
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Difference between Magnetic South & Solar South?

    Local topo maps, or google earth will reveal true North (or south). You can also look at the sun! The highest point of the sun durning the day will reveal true south. (Remember, not at clock noon, but solar noon. Just watch your sun for a few days around noon and you will see where it is. Or for a more esoteric way, find the sun rise/sun set locations on the solstice. Everywhere on the planet, the sun will rise due east and set due west on the solstice, revealing that south is 90 degrees off those angles. Or, get up early, mark the sunrise location (assuming flat ground), then mark the sunset location, due south is directly in between. (Simple GPS will tell you as well)

    Lots of ways to skin the cat.

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Difference between Magnetic South & Solar South?

    I've always liked the Shadowless Stick method, or the Stick, Shadow, Duck method:

    Use a stick, stuck in the ground , put a stack of pebbles (a duck) where the shadow is. Every 30 minutes, mark the shadow again, you will have a true E-W line, and can obtain N-S from that.
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    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Difference between Magnetic South & Solar South?

    or use a stick and do this at solar noon and the resulting shadow line is a north/south line. remember solar noon is in the exact center between sunrise and sunset times and these are often given by weather forecasters.