Newts of same focal ratio will have the same field curvature, i.e., the FC of the parabolic mirror. So I find it puzzling that in one brand of Dob (Discovery) the EP displays no FC while in another brand (GSO) it shows a severe case of it.
I would still like to see one of these EPs for myself...
Edit: Above I wrote: "Newts of same focal ratio will have the same field curvature". INCORRECT! Newts of equal
focal length have the same FC. Focal ratio has no bearing on FC for a given focal length.