(Brian Tung) wrote in message ...
Stephen Paul wrote:
There are yet two other affects called pin cushion and distortion. On these

Distortion is variation in magnification with off-axis angle. If object

Sorry folks, my mistake. I'll check terminology in future! Where I
said "field curvature", I should have said "pincushion distortion"
(the first phrase just seems more appropriate in normal "english"
usage). With the 31mm Nagler, the 80ED is focussed across the entire
FOV, but lines get distorted towards the edges. Not a problem if
you're just enjoying a wide field view "eyes only".

Cheers
Beats