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Coma and magnification
That's the issue. Seeing artifacts will impact the evaluation of coma at higher powers.
I can tell you my experience:
My 5 and 7mm Naglers display coma in their outer fields, so I use a Paracorr for every eyepiece. But they exhibited only annoying, and somewhat minor comatic images at the edge.
My 35 Panoptic, on the other hand, exhibited a starfield that looked like I was standing on the deck of the Millenium Falcon going to lightspeed. The star images looked like radial streaks.
After the Paracorr, the star images are perfect to the edge in the 5mm and 7mm, yet still a tiny bit comatic at the edge in the 35mm. [I have 43 years experience looking at star images through hundreds of scopes, so I am compensating for the tiny amount of positive field curvature in the 35mm]
If simple magnification explained the visibility of coma, coma should have been MORE visible in the 5 and 7mm (82 degree fields) than in the 35mm (68 degree field), yet it patently was not even in the same league.
Here's what I think: Star images are not magnified. They appear the same size in all eyepieces until the Airy Disc is visible, and then start appearing larger. The 5mm eyepiece is a 1mm exit pupil in my scope, yet represents my highest magnification (I'm not a planets or double stars observer, so powers above 400X aren't too useful to me, on an undriven scope), but that magnification *just* makes the Airy disc visible.
Accordingly, the only factor having an influence on what coma I see is field stop size in millimeters--a wider field stop will display more coma and magnification has nothing to do with it. Doubling the power doesn't increase the size of the star image because the scope sees it like a point source. It is only the reflection that is comatic. The eyepiece is just a simple magnifier of the focal plane of the telescope. So, doubling the power with an eyepiece of identical apparent field doesn't show the same amount of coma; it shows less because the field stop is smaller.
In other words, you'd have to keep the field stop the same size to see equal amounts of coma at all magnifications.
What do you think? I think that may just be the explanation I was looking for.
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