Bill, is there a significant image shift when focusing? If there is, then when your wiggling the focus knob back and forth one part of the primary can be further forward/back than another.
There *shouldn't* be that sort of curvature of field in a C11. Unless it's a property of the eyepiece.
There *shouldn't* be that sort of curvature of field in a C11. Unless it's a property of the eyepiece.
