Hmm pretty good
Try with external aperture (f/4 of more... you can cut it out from black paper with help of
compass ).
I was playing a lot with canon FD lenses (
see 200mm for example), and the results with external aperture were generally the way to go to get rid of CA and coma.
Also, try to focus with Bahtinov mask, use F or G-type stars for that.