Last month I had collected data from M42 with to different setups. One is a mirrorless Fuji OSC with a 72ED scope, the other an ASI1600 mono on an 130mm F5 newt, with H-alpha filter. I liked both images. One because of the color, the other because of the detail.
That's when I thought: why not try to combine both images? And it actually worked! However it took some fiddling in Photoshop with rotating and scaling. Once I got them close, I could use PixInsight for star alignment and dynamic crop.
My question: is there a way to automate or calculate the amount of scaling that is required to be able to fit them? I noticed star aligment did not work before the rescaling. I figured image scale can be a key figure, but I cannot get my head around the 'how'.
Here are the separate images and the result of the merger. I also like how the Ha-layer makes the stars smaller. Unfortunately the Fuji creates some strange color artifacts around the stars, maybe in combination with limited color correction from the ED-scope.