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You can also use the astrocompass as a way to use the zenith to determine direction due to polarization of sunlight. This was developed during the early days of trans-polar flights often called a "zenith compass." I set mine up to see how accurately this can be done.

I balanced the polarizing camera filter on top of the sighting vanes one
the astrocompass. I cut out a piece of cellophane and put it on top of
the filter. I put a small mirror on the base of the astrocompass to
allow me to look up though the filter at the zenith. I had to try
different alignments of the cellophane to maximize the zenith light
shift affect. See attched images.

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