Unexpected shape of focus area (1 Viewer)

[Jviana]

This was to be a simple test to the autofocus of my CP990 with a Swaro AT-80 HD.
But the shape of the area in focus call my atention and I can't find an explanation for this.
Can you help me to understand why this area has the format of an half moon?
Lack of paralellism between the camera objective and the sope ocular?

 

[Andy Bright]

Probably down to the curvature of the eyepiece.... they are made for the human eye which is curved and not for cameras. It's most notable when you zoom out to a wide angle on the camera, so that it is looking at a greater area of the eyepiece.
I'm currently testing a specialised digiscoping eyepiece, which is flat... everthing is in-focus from edge to edge.
Regards,
Andy