I have a one year old CGX mount carrying an Orion 190mm Mak-Newt (only 20 lbs) with a ZWO ASI-294MC-P, and PHD2 guiding (ASCOM connection to base of HC = hand controller). Normally I do stacks of short frames using Sharp Cap, which gives excellent results. Recently I started trying long single exposures of up to 30 mins, and discovered that my stars are badly smeared in RA. PHD2's GA confirms that I have large RA peak-to peak motion, of like 50 arcsecs, in these images.
I have read that this is likely due to worm gear error (478 sec period on a CGX), and periodic error corrections (PEC) can be stored in mount memory using PEC. (In the HC, PEC is under Menu > Utilities > PEC.) However I can't find any instructions for actually doing (and checking) PEC on a CGX. My downloaded manuals tell me to look elsewhere, e.g. under Astrophotography, but they don't say where.
Can anyone suggest instructions for running PEC on a CGX (presumably using the HC), or even better discuss their personal experiences?
I tried just running it on the HC but there is no visible improvement in star images.
A recent image (single exposure, 16 mins) that shows the problem is attached.