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Paul,
while I agree with Eric, forget the "imperfections" right now, and get the hang of crawling, before being expected to walk.
Focus is difficult to ascertain in an image, well I find it difficult anyway, unless there is sometime to benchmark it on. Lets say you have it pretty good here.
Now go shoot something like a galaxy, try the 4945, or something you can see. Do all the focusing bits again, and see what the star sizes look like with the galaxy in the shot.
If 5 minutes is all you can get, then do 5 minute subs, just do lots of them. Try some with and some without the light pollution filter too, but be aware that the filter may alter the focus.
Stack them and come back to us. A dozen 5 minute subs should be a good start. If you get a cloudy night, tinker with a library of darks and bias frames. Just settle in your head a temperature set point, I use -20º C, but it could be anything up or down from this. Settle on this and shoot some darks, at the same temp, and at the same exposure duration you figure you will be using. In your case shoot a dozen perhaps at 5 minutes, and another at say 3 minutes. Bias are simple, they are as short as the camera will allow. Store them in a folder, Bias in a sub-folder, darks in another. Then the only variable is the flats, and unless you have a semi-permanent setup (focuser/camera/focus point/scope) you need to do these at the time you image. Try one next time you image though, as this should alleviate the snags Eric is talking about.
Lots to do, but look on the bright side, if you didn't have a one shot colour camera you would need all this at least three times, LOL.
Gary
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