[Todo43 (Lachlan)]

Hi all,

I have had this issue for a little while now and wondering how I can fix it in post-processing. The attached image is a starless image of the Christmas tree cluster. Taken from a Bortle 1 sky, I had 3 hours and 5 mins of 5mins subs.

Gear is Skywatcher NEQ6, Sharpstar AL90-R scope, ZWO ASI533MC Pro

In the top right and bottom left corners, the image is very splotchy with a sort of mottled colour. Other than possibly having data there that I just don't have enough exposure time to pull out, what could be happening? Is there an issue with my workflow that I might have?

My workflow is as follows. I almost always use Pixinsight for the entirety.

- Stack in WBPP using bias, darks and flats

- Extract Channels from master and linear fit

- Recombine images using Channel Combination

- Dynamic Background Extractor placing reference points on areas with very little nebulosity. In this case, it was the splotchy mottled area. About 10 points per quadrant

- Background Neutralisation

- Spectrophotometric Colour Calibration

- SCNR

- NoiseXterminator

- BlurXterminator

- Stretching using Arcsinh then onto histogram transformation

- Curves transformation for contrast correction and small adjustments

- Star Reduction using EZ Processing Suite EZ Star Reduction

- Saturation Increases using Curves Transformation and sometimes a hue change

- Finishing touches using Curves transformation

Just wondering as it has happened in other images as well. This was taken in B1 so thinking its not caused by light pollution.

Happy to provide examples of other cases that I have had.

Your help is much appreciated!