Nice images Marc. I had a play with star reduction with ImagesPlus in the blue and red channels of your LMC image. Must have been a reasonable dark sky site.
Large image here 6MB
http://d1355990.i49.quadrahosting.co..._12_SRrb_L.jpg
You would get better than this without the far UV.
A UHC-S filter would cut the UV and increase contrast. Try mounting your 48mm UHC-S infront of the lens. This would also act as an aperture of about 43mm and would give you about f/4.6. A Hutech 58mm LPR filter with an open aperure of 53.4mm would get you f/3.75. Most of the CA comes from the outer part of any lens. Even my 300mm Canon lens has slight red and blue at perfect focus from IR and UV as photo lenses are not designed for IR and far UV only visible.
A good LPR filter would also cut the UV.
A longer lens hood would also increase contrast due to to light outside the image area scattering inside the lens that adds to apparent sky fog. A front aperture also stops light from even hitting the inside 'walls' of the lens.
I have been imaging with the one lens (Canon 300mm F2.8L) for years at a light polluted site and have managed to improve by all these little methods that by themselves seem negligible but when added together make all the difference.
Hope this gives you some ideas to try.
Bert