Quote:
Originally Posted by Don Pensack
Obviously, some people are much less sensitive to a reduction in illumination than others. I could see vignetting in the 8" SCT with any eyepiece having a 38mm field stop of larger. It didn't bother me that much, but I could always see it.
The C8 was designed to fully illuminate a 1° field, according to the white paper, and anything larger would result in more vignetting than the 50% illumination at the edge that was designed into the scope. I found I could tolerate vignetting up to about 1.2°, but not larger. A 46mm field stop yields 1.3°, and vignetting was definitely noticeable 100% of the time.
I could also see it in my 127 Maksutov when the field stop was larger than about 25mm. I never used 2" eyepieces with that scope because vignetting would have been severe.
Some use no coma corrector at f/4. I found coma horrible at f/5 and bought a coma corrector the next day after getting the scope.
We all have different sensitivities.
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Interesting you should say this. As I said, i have gone out of my way to look for vignetting, observing under as many conditions as possible to make sure I wasn't missing anything. I have never seen it in these scopes. You are the first person I have encountered who has said they have while no one else has who has also made a point of looking for it. Not questioning your observing skill which for me is never in doubt.
Different sensitivities is also very nuanced. There can also be many reasons for why different people see things differently from others, such as eye health, gender, age, genetics and others. I have noticed changes in my own eyes over the years and I wonder just how many people are honest enough with themselves let alone with others. As for what different people are able to tolerate or not in what they see, that's different again.