Beautiful results Leo, I love the colours, I get lambasted by a few for saturating my colours sometimes
but I think it looks great
I like the way you have kept the dynamic range of M51 a little more believable than most who process this galaxy. To look
real to me the core should really be noticeably or at least slightly brighter than the arms, most however process the core of M51 to look darker in order to reveal the inner details and this makes the galaxy look hollow and somewhat unnatural. By maintaining the brightness across M51 you have at least stopped short of this and still showed some core detail - nice work
Mike