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So I combined my narrow band images with the RGB combine tool, and I seem to have some weird gradient in the corners and edges of my image. I tried to use the light pollution removal, but that just made the image worse, then I got to thinking that narrow band shouldn't have a lot of light pollution especially at 3.5. I believe that I'm missing something, just not sure. below is a screen shot of my image, any thoughts and ideas would be appreciated. I know that I have some vignetting too.... I've sensed adjusted the back focus to reduce that and to get rounder stars all the way to the edges.
Thanks
Zach
I guess you are using flats per filter?
No, that is correct, but I would've assumed that (given they are working ok), the vignetting would be taken out. So I'm suspecting an issue with the flats possibly.
@vincent-mod I think your right about the flats, I went back and looked at the master flats, and not sure what they should look like, but mine don’t look awesome. I’ll have to work on getting better flats. Since taking this image, I’ve adjusted the back focus ( actually increased it to reduce the vignetting and get round stars further out to the edges). I’ll have to try and take some practice flats and work on that.
Good ideas, you need to look out for proper illumination of the sensor with the exact setup used when taking the lights. This means that you can go down a bit with the gain (to increase dynamic range) and to illuminate so that it doesn't clip on either side of the spectrum. Preferably get it more to the right than the left (the 50% which is used a lot is just a guideline, with 60-70% you can get better illumination possibly). Make sure to illuminate for 1-2 seconds per flat sub and of course use darkflats (darks with the same exposure and gain as the flats) to calibrate them.
@vincent-mod I do use dark flats, I’m using NINA’s flat wizard with a Pegasus flat panel. I know that I set the 50% mark, and the exposure’s were all fairly long 10-30 secs if I remember. I will work on this, in the meantime, I’ll have to figure out a way to kinnda salvage my image 😀. Thanks
