Some advice regarding pier flip

I asked this over on the Gemini 2 group, but thought I’d ask here as well.

I’ve been having some issues with pier flips lately and wanted to solicit the collective wisdom of the group. I don’t believe this is a “problem” or “bug” with Gemini or other software. I’m using a G11 G2, pier mounted, TEC140 and STF-8300M.

For a long time pier flips worked flawlessly. After the pier flip the plate solved image would usually be within 100-150px of centered. And after 1-2 iterations of plate solving the mount would be precisely pointed within 10px of the target. Lately however after the pier flip the mount is more like 600px off from the target position. Last night for example after the flip it was 654px off. After 3 iterations of plate solving and centering the mount got to within 150px of the target. But on the next plate solve iteration it went back to 500px off from the target position.

Could this error in target position be caused by an insufficient pointing model in the west? Plate solves work quickly and flawlessly in the east. There have been times where SGP failed to center the target at all after the pier flip.

I’ve been scratching my head over this problem for a while now, and am at a loss for what is happening. Any advice is much appreciated.


I use eqmod, and do not use a pointing model, just good polar alignment …
I found that pointing model made plate solve and subsequent slews behaving erratically.