Hi all,
Finally managed to get a night of good seeing after months of clouds, what strange summer weather aye?
Anyway, I've determined that the aberration I'm seeing in the eyepiece is not due to field curvature, however when I defocus a starfield in the eyepiece I see the following distortion of the telescope aperture and secondary shadow.
Am I correct in interpreting this as being astigmatism within the eyepiece and not coma?