M45 Blue Filter Haloes

[gnomus]

I've been trying to gather some RGB M45 data in between rain, wind, fog and so forth.  The other night I managed just shy of a couple of hours of blue (23 x 5 minutes).  I use the Baader LRGB CCD filters.  Overall, I was reasonably happy with the nebulosity I got but many of the stars had quite significant haloes around them.  I don't have reasonable R or G data yet, but the odd 'test' image taken with R & G do not show any significant haloes (at least that I can see).  I am using a WO Star 71 with an Atik 383L.

I have seen a number of M45 photos.  Many do have haloes, but a fair few seem able to have avoided this.  Any suggestions as to what I can do to reduce my halo-ing?  (Incidentally, I have had a go at the PI halo reduction script, but don't seem able to get anywhere with that - even though I can reduce the halo, I seem to leave tell-tale signs which to me look worse than the haloes themselves.  I am sure that this is down to me and not the tool itself.)

[Edit:  I should maybe add that the blue data was captured around the meridian - the flip came just before the last 3-4 captures.]