My First Half-Decent Jupiter

[Superdavo]

Hello Everyone!

On the 30th of December, I spent some of my Christmas money on an infrared filter, and (remarkably!) it was clear enough for me to have a chance to try it out that night! Unfortunately, I didn't have enough time to take some exposures of the moons, but I was lucky enough to capture a transit of Io. 

After a long time processing, here is what I got:

Taken with DMK21, gamma approx 100, gain approx 600-700, exposure about 1/30s, Focal Length 3000mm (F/20), 3 minutes (about 4,000 frames I think), of which 2,000 stacked, with a strong wavelet applied, before a lot of post-processing in Photoshop.

It's probably the best I've had yet (by a good way), but I have a few questions:

1. The image seems to suffer some vignetting, whereas many photos I've seen are relatively 'flat'. The vignetting was introduces by my photoshop editing (Mainly when I altered the levels or increased contrast) . Anyone know a way to avoid that?

2. To increase the brightness, I had to decrease the framerate quite a bit, but I've seen people using much higher focal lengths get a fairly high amount of frames, and not have too much noise, so how do they do it?

Thanks for the help

David