Hi bwa, Lex, MIkeM and ruitripa!
Thank you for the friendly comments to the image.
> MikeM: I didnt use an Ha filter, because 'red' is strong enough in this field and its not so easy
to mix Ha with RGB frames to get fine colors (at least for me). Extra Ha frames are an advantage for faint nebulas and fragile Ha regions in galaxies only. For example, at the moment I'm trying to get out the Ha tails in the center of M 106 - on a 40min singleframe there is almost 'nothing'.
I will report my result.
Best regards.
Herbert, Austria