Another post here got a little off-topic as we considered the moon's impact on Oiii, and I figured I'd do a test tonight since the moon was out/bright and I'd pulled the gear inside last week because of severe weather (ie .. almost a full 1/10th of an inch of rain over the last week! ) and I needed to break things back in.
So, after getting everything setup and running, I slewed off to the east, ran autofocus on my Oiii filter (3nm Astrodon), and then took a series of 10 minute guided subs. The first was 45 degrees from the moon, the second was 30 degrees from the moon, the third was 20 degrees, and the 4th was 10 degrees- but it experienced 'technical difficulties' and wasn't used. I tried to keep the aimpoint for all the tests close to 45 degrees of altitude to keep things consistent.
I was mainly testing for gradient; looking at how close to the full moon I could image with my particular setup. Of note, my scope has a tiny lens shield - normally I add some foam to extend it but I ran into problems with it so I went with just the lens shield with the AT65EDQ. I normally will shoot no closer than 40 degrees to the moon - but that's just a number I used without any real basis behind it. So tonight I tested.
So, using the three 10 minute subs (45, 30 and 20 degrees from the moon), I ran ABE to look at the gradient, and ran image stats and then stretched the image and ran AberationInspector. Here's the results:
Degrees from the Moon
20 30 40
Mean 1827 1213 899.7
Median 1841 1217 901.3
avgDev 101.5 37.59 12.76
MAD 116.6 42.15 12.74
minimum 1644 1128 868.4
maximum 1970 1266 918.7
and here's the AberationInspector views:
20 degrees off:
30 degrees off:
45 degrees off ...
Based on this testing, I'd probably be willing to shoot a lot closer to the moon. Although the gradient is noticeable at 30 degrees, it is smooth and easily corrected in PI. 20 degrees started showing problems, but I feel a better lens hood/shield would cut down on the glare enough to make it workable. Any closer than 20 is pushing it with my system.
I had planned on some more tests, but the gremlins came out in force and I decided to shut down for the night - maybe more tomorrow. Hope this helps.