Easier Light Pollut...

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Easier Light Pollution Correction  


White Dwarf Customer
Joined: 3 years ago
Posts: 11
August 7, 2018 15:04  

By far the most time-consuming and tedious step in my workflow is the light pollution correction - often I just need to fill the image with squares, except for the bit in the middle which contains the main subject (galaxy, planetary nebula...)

While I understand that full automation would be hard, there should be some kind of way to select large non-square portions of the image and 'auto-fill' them with reasonably sized squares - that way I can concentrate on correctly marking the more difficult parts (for example gradients near the edge of the image or the single hotspot that is often present in my images.)

Even the ability to re-use the boxes drawn for one channel on the other registered channels would reduce my work by *a lot* - in many images, the "sky background bits" are the same across channels even if the gradients themselves are not identical, so I'm finding myself performing the exact same tedious task 3-4 times in a row for LRGB.

Alternatively, a bit like using Photoshop with Gradient Xterminator - there I can draw a freehand selection around the bit(s) I want to ignore and it'll base its reprocessing on the bits outside that selection, no need to draw squares at all.

I absolutely love lpc's ability to remove the effects of light-pollution gradients, but I loathe the amount of clicking I need to do to make the magic happen.

Quasar Admin
Joined: 3 years ago
Posts: 2241
August 7, 2018 23:08  

Hi Bart @bdeclerc,

Scientifically, automating Light Pollution / gradient correction indeed is very hard...

I my own experience,  in most images just a couple of big boxes will do the trick, unless you simply have very severe gradients or experience different gradients between imaging sessions for example. In a lot of cases, I only needed to place 10-20 boxes to get a good result.

I have been thinking about how I can make the tool easier. I know for sure that I can make the calculations a lot faster, so I will work on that soon.

Then I want to provide the option that APP will make a suggestion of boxes to place using a new algorithm. That should then help as a starting point I think, but for some images this will simply not work I am afraid.

In complicated cases, the only way to get a very good correction is by placing the area select boxes step by step and clicking calculate in between to verify if the result is good or not. It's mathematically very hard and the lokation and size of an area select box determine both the outcome. Sometimes, you need to replace the box or resize it to have it work better. This has to do with the mathematical model involved which are regularized Thin Plate Splines.

I will think about your suggestion of adding the option to remember the placed area select boxes between different channels and how to implement this.

Thank you for sharing your experience in this regard, and I will make sure that the tool will be improved in the upcoming versions.

Kind regards,


Main developer of Astro Pixel Processor and owner of Aries Productions