Integrated Image Cluttered and Messy

Oeh that is a bit of an issue indeed. This is definitely a problem with optics or calibration data. Normally you shouldn't need that many light pollution rectangles to fix gradients, a gradient is usually more gradual (hence the name 🙂 ). So this is a different issue that needs to be solved before processing I think.

Can you show a few screenshots of how the flat, bias, dark and single sub of the subject looks like?

@vincent-mod Yes, I'll put them up later today after work.

@vincent-mod I've attached the requested frames. In order left to right are Bias_ISO1600, Dark_ISO1600, Flat_ISO1000, Flat_ISO1600, and Light_ISO1600_180s.  My bias and darks are all taken the exact same way just with different ISO setting so if there's an issue it should be common to all of them.  But I think I already see the issue and, unless I'm off my mark it's my flats.  From the camera preview they looked ok and around the middle of the histogram but in APP they're really underexposed.  I honestly never checked them in APP before now so that may be my problem unless you can see some other issues.

It's a bit difficult to see with DDP off. 🙂 If you could switch that on just to see a bit more how the noise looks like etc, that would be great. For the flats it's best to judge them by leaving DDP on, but selecting "no stretch" under that button. The most important thing is that a flat is not clipping on the left (the histogram should show a nice continuous profile). But I think the main issue with that first image is light pollution and vignetting or some combination of that. Is it a mosaic?

@vincent-mod No I wasn't going for a mosaic, I shot more or less the same point both nights trying to get the nebulae and wanted to just focus on those.  I live in a Bortle Class 5 so there is some light pollution but usually as long as I don't point near the horizon towards the city it's usually pretty clear overhead.  I've gotten some fairly decent results of Andromeda and Orion with this same setup but I used a different part of my yard, so I wonder if I wasn't getting some light from a light on my neighbor's back patio in these frames. I've attached the same frames with the requested settings if that helps to deduce where I went wrong.

Frames go Light_1000, Light_1600, Dark_1000, Dark_1600, Flat_1000, Flat_1600, Bias_1000, Bias_1600.

Thanks. I suspect light pollution indeed as it seems your darks don't have a lot of amp glow going on. A light nearby will definitely also cause issues if it can't be blocked from the view of your lens. Do you have any data in which you're sure there was no light on?