Ah, of course it's HaRGB. Really cool. I'm curious, you de-star the color layers or leave them as is when combining channels? When I've tried HaRGB, the Ha layer has the best/smallest stars which means that the RGB color layers end up leaving rings of color on the background around each star.
I don't remember exactly what I did, but I do remember running into that kind of problem. I probably used starnet2 to remove stars before doing much processing, and recombining stars towards the end.
