Trying to reduce drift in RA using internal guider. I find guiding is much better when I turn GPG off? I am confused because GPG predicts the main worm period correctly within a few tenths of a second of the theoretical period of 198.07 seconds for my EQ8-R Pro. This tells me its seeing the PE but isn't correcting it correctly. What setting should I look at?
I am taking narrow band images with exposure times of 300 - 600 seconds. With GPG off stars are slightly egg shaped in RA direction need to be zoomed in close in viewer to spot this. (almost acceptable) With GPG on drift is bigger with stars extended into a short pattern with a couple of bright spots. Any suggestions out there please?

Some questions.
When re-using calibration is the PEC pattern measured by internal guider stored on disc? ie is PEC re-used?
How long does it take to synchronise GPG with the worm cycle. Not sure how the EQ8-R Pro works but with a Meade there was a magnet on the worm shaft that went past a sensor. With a 198 second period (3.3 minutes ish), can it take up to 3.3 minutes to synchronise with the worm? I would like to understand how indexing works and how EQ-mount driver finds this out?
After a slew I think guiding is turned off then back on again. Does this mean I should wait at least 3.3 minutes for GPG to kick in before starting the next image (assuming I can get GPG working)
Is there an optimal arrangement for aligning the guider sensor? By eye I try to line the sensor parallel to RA/Dec but does this matter. Maybe its best to rotate it so it's at 45 degrees and RA drift is diagonal across pixels?

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