Re: PA Error what is acceptable for 530mm FL & 2.1arc sec/pix
Shailesh,toggle quoted messageShow quoted text
I was trying to make the point that even permanent piers can shift, especially if placed in soil with any amount of clay. For example, it's common here in California, where clay soil is abundant, that as the clay gains or loses water the clay expands or contracts. This can happen very quickly. Because of this, cracks can form in sidewalks and exterior (and interior) walls in homes. Clay soil can even unlevel homes, so a pier can be easily affected. So despite your pier being solid, the ground around it might shift and move the pier. I hope that makes sense?
That said, it could be that the mount's polar alignment has shifted for another reason (e.g. alignment changed when the mount bolts were tightened).
BTW, did you perform the Plate Solve and Recal in APPM? If so, did it help? If not, something physical in your setup may have changed. If so, you could do another APPM run and compare pointing terms to see what has changed.