Well, I just purchased a Skywatcher 14 inch go to Dob. After hours of cool down time, I did a star test. Attached is a drawing of what I see. Just inside "focus" (I use the term loosely, there does not seem to be a sharp focus), the secondary shadow is enormous. Just outside of focus, I can't even see a secondary shadow. You can see the significant difference in the secondary shadow far inside and outside of focus. I believe this indicates significant undercorrection. My mirror is too much like a sphere. Can anyone with perhaps more knowledge than me tell me how bad (or not so bad) my mirror is?
Attached--drawing of out of focus star