mike60 said:I believe that i get more definite 'black out' on bright sunlit days with lots of reflected light than in dimmer conditions using my Zeiss 10x40. Does this stack up technically?
Me too. This is from the astrosurf-link above (the bottom of the page):
"...when the exit pupil is very large and close to the size of eye pupil, looking at the edge of the field your eye pupil will cut off a part of the light cone in the medium field region of the eyepiece. That medium field become dimmer while the center of the field of view is unaffected. You see blackout areas in the field. When the exit pupil is small, the effect is less apparent as your eye pupil can more easily move inside the light cone, this last having more place to browse your eye pupil. The "blackout" effect mainly arises with eyepieces of large eye relief and exit pupil or barlowing a low focal eyepiece as a 35mm."
Ilkka