Posted this on Cloudy Nights, but no one seems to know the answer, so here goes:

I want to use my dslr for prime focus photography with my Nexstar 8SE using a 1.25" adapter and t-ring. I found this site:

www.telescopeadapters.com

I talked to a guy there and he said that their 1.25" and 2" adapters are both threaded for filters. Since I have 1.25" filters, I want to get the 1.25" adapter so I can use my filters.

Now, my question is will I see any vignetting if I go with the 1.25" set up? The camera I will be using is an olympus e520, which has a smaller sensor than APS format cameras, so Im hoping I wont see any vignetting.

Here are the specs on the ccd in mm:

22.500 (diagonal)
18.000 (width)
13.500 (height)