I've seen so many people moaning that doing this sort of set up and testing has wasted hours of precious imaging time...

The mount property that defines pier side is actually the declination axis position. For one pier side the axis position is in the range -90 to 0 to +90 and in the other +90 to 180 to 270/-90.
If you are at a dec of -30 and do a pier flip the hour angle axis moves through 180 degrees and the dec axis from -30 to +90 to 210 for the Northern hemisphere or -30 to -90/270 to 210 in the south. The mount alignment model sorts all this out to give you Ra and Dec.

You can't use Ha because if you track through the zenith the Ha goes from -ve to 0 to +ve (or just under +12h to +12/-12h to just over -12h) The pier side does not change. Really pier side is a poor name, pointing state would be better.

Some mounts also change "pier side" around + or - 6h hour angle, this makes things OK to the N or S but very worng if you move between the two. There's one driver that uses Ha for the -4h to -9h and +4h to +9h range, the mount reported pier side close to 0 and +-12h except for declinations close to 90 where it reports unknown.

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