Jimmy,

I concur with Don. I do not believe your approach in assessing the center mark location is adequate.

There is a much simpler approach. You do have the Catseye tools; therefore, it is fair to assume you still have the transparency template that comes with the tools. Use that template to assess the placement of your center mark.

By the way, all ghost reflections can still be stacked precisely even if the center mark is slightly off.

I still strongly believe your problem is simply a rotate/tilt issue. Based on your drawing, the discrepancy between the primary and secondary mirror edges it too large to be contributed to a “slightly” off-center mark. The center mark will have to be an inch or so off to create the scenario you have described which I doubt to be the case.

Jason