What do you mean with the sentence: Maybe you need to catch only a suitable cut circle between each HOLZ and the Ewald sphere?

Thanks Volker, I will think about it. At the moment (I am somewhere in a hotel) I still don't see the formation of rings, especially the formation of rings of several pixels width (e.g. typically visible in schreibersite patterns). I will post next week some pattens which show these efects. Greetings, Gert