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Compasses and compass phone apps are not ideal for finding accurate True South , they are prone to calibration errors based on the surrounding magnetic fields in your location ) mainly from the type and composition of Iron in the regolith in your region.
A friend who use to hike a lot , gave me an expensive Silva compass ( with magnetic declination) which I used to try and find True South at both my observing and imaging locations.
After using the Solar Noon Shadow method at both locations , the Silva Compass was anywhere between 5 to 8 degrees out. Project that error up to the night sky and your a long long way from the Pole.
In fact, the Compass slightly gave variable results each time I used it. ( So did my iPhone )
Gave the Compass back to my friend.
My experience with compass’s and iPhones ………
Martin
PS: My Solar Noon Shadow lines are permanent marks and are accurate for at least the next 10 years.
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