To accommodate a 2" filter wheel, which has an M48 aperture, I need to find the shortest 2" eyepiece holder, and I found the one in the link below, with external length 40mm, internal depth 35mm, and withT2/M42 constriction:
My Explore Scientific 82 degree 30mm has a field stop diameter of 43mm, according to official specifications:
I measured the, ES82 30mm barrel length is 38mm. I will use a parfocal ring to insert it 28mm inwards. This will make my ES82 30mm parfocal with my 1.25" eyepieces.
I suspect the light cone should have a diameter of 43mm, but the diameter may be even larger at the point of 42mm constriction. My question is how much larger, and how bad the effects of vignetting should I expect?