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Sorry to be a fuss pot, but I'm curious about your 40mm eyepiece. Being a plossl, it should work well with your Newt. Despite the large exit pupil, even from urban skies the most you should have noticed is the shadow of the secondary mirror. Maybe a chance then of an on axis diffraction pattern, but I have my doubts. I'm happy to here other people's thoughtson this as i just don't recall ever having seen such an aberration in my Newts while even using a 55mm plossl. Being an optical match, plossl with Newts (slower ratios more so), I am surprised at the aberration you've seen.
Mike, are you positive that the 40mm IS a plossl? Just that I am most surprised and intrigued by this aberration you've seen .
Not discouting the possibility of dew, external or intrenal condensation, but even that seems like a curious artifact to see, an on axis de-focusing with a plossl, even at f/5.
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