Thanks Dave and Alex. Yep, this one is not straightforward and I'm collecting more data (last night and tonight) - Ha, Oiii and LRGB data. Luckily the moon isn't in close proximity and the subs are looking ok with the usual gradients to control. I did a quick preview with Ha added and it brings out the reddish active star forming regions quite nicely ... apparently they're not SNRs Dave, but very active stellar nurseries within curiously round-ish gas clouds (
source).