PHD2 has the ability to take a rotator's PA and compensate for it's guide calibrations so you don't have to re-calibrate after every slew/rotation. However, PHD2 only talks to ASCOM rotators. So, question is: does the Ekos internal guider consider a rotator PA in it's calibration? If not, does it know to recalibrate after a slew/rotation?

I haven't been following all the rotator changes closely, but from a quick look, it seems like Ekos does not take the rotator into account with respect to reusing calibration.
Therefore, you'd need to disable re-using calibration if you were rotating the guider's camera position.

FWIW, it's doable, but not quite as simple as that, as the rotator might not have an effect on re-using calibration
(e.g. if the rotator didn't rotate the guide camera, but only the imaging camera, then it would not impact re-using calibration).

Yeah, re-calibrating after every slew/rotate is a pain and takes time, but where it really takes a toll is if you're imaging near the pole where calibrating is not very accurate and error prone. I've made the request for PHD2 to talk to an INDI rotator - that would be best I think.

There's a pull-request out to add INDI rotators to PHD2. I've pulled the PR, merged into latest 2.6.12 master and built it. Now have connection to my Falcon rotator in PHD2. Now just need some good weather to see if it works!

Forgive me, if I do not understand the problem. But I think all this "solutions" are obsolete: Just use the up-to-date pulse guiding via mount and you're done! Right?

I guess I failed to mention I have an off-axis guider setup behind the rotator. If the guiding system talks to the rotator to get it's position angle, it can compensate it's calibration for changes in position angle when the mount slews and aligns to a new target. Otherwise I have to recalibrate guiding every time. This becomes a significant issue with the greedy scheduler because it can jump out of a lower priority job and slew to a new job.

I have the version of PHD2 that talks to the rotator compiled and built here. Just waiting for good weather to test.

OK! I think I got the "picture". I will analyze the calibration code and make a stab at it.