[raymo]

There should be minimal processing necessary at this basic level. Start from
basics. Take one 15 second exposure, enlarge your playback image on your
LCD screen and make sure your individual exposure is well focused.
If focus is good take a couple more, and stack them[in DSS if that is what you are using]. DSS contains all you need to produce a good image at this
basic level. Align the three colour cones, and move them left or right to produce a nice not too dark sky background; reduce the highlight if the core is
over exposed, and saturate the colours to the desired level. All done.
I assume your Bahtinov mask is the correct size for your scope.
As an alternative you can enlarge the stars in LiveView and focus that way.
Its possible your focus is o.k. the pic is so enlarged its hard to be sure, even when downsized on my laptop.