This question is simply to satisfy my curiosity.  To create the factory installed PEC curve I assume each mount must be tested and track a star like source moving at sidereal rate for several worm gear cycles.  Doing this on a real star under the night sky would seem out of the question as it would require many clear nights and much time/effort to do for each mount produced.  That would seem to leave an artificial star that moves at a simulated sidereal rate on a test bench?  Or is there another method I haven't thought of, perhaps using encoders?

Thanks,
Scott