True south is best solar panels orientation for maximum exposure of the solar panels to the sun.
Facing your solar panels true south ensure your solar perform optimally from sunrise to sunset.
Note: true south is different from magnetic south. The calibration on the compass indicate magnetic South.
To get the true south best for solar panels orientation at Northern hemisphere. The Angle of declination of that particular area must be knw.
Then aling your compass to angle of declination, this will shows the true south of that area