Thanks Jeff and Brett, I had to adjust the colour a bit because straight out of Registax into Photoshop it looked a bit bland with less colour variation between the disk and rings. When I shoot Saturn with my DSLR the rings always look too blue so I think the bayer matrix filters on the Canon 550d sensor must be different to my Meade RGB filter set. I just tried to match the Hubble Saturn shot for colour correction. The colour's still not right to me but it's the best I could get from the data I had. It also depends on the exposure you give each filter. I think I overexposed my Blue filter shot a bit too much. I've also found out my parfocal filters aren't parfocal, with the blue filter requiring an adjustment to the focus.
