I’m not really seeing much if any FC with either one. Maybe some with the ES (I suppose inherent FC from the scope will be more obvious with wider AFOV). I see some RD, especially with the ES as expected. The ES has wider AFOV so it will have more RD. Plus the XWs are designed with spotting scope use in mind, so they don’t have as much RD. Better for terrestrial observing that way.
It is interesting, because everyone knows a F5 refractor has field curvature, and everyone knows the 20XW has field curvature. But that is a really sharp looking field stop to me. I almost wonder if the FC in the XW might be opposite and be canceling out the FC in the refractor? The XWs were made with spotting scopes in mind so it might not be a huge leap to think they might have designed in some FC in order to cancel out the FC in a typical F6 spotting scope.
Oops...maybe, perhaps I’m confusing FC to pin cushion distortion..
Edit: I deleted the photos as didn’t want to confuse anyone.
Edited by Gastrol, 23 February 2021 - 01:28 PM.