Advice please - de-noise on a mask

[DavidS (David)]

Hi there

I would appreciate some help on how to prepare a mask because I am currently editing a mask by hand and this seems stupid because there must be a better way. Attached is a range mask with a lot of noise. I have tried PixInsight TGVDenoise but it doesn't appear to help. I would appreciate some pointers !!!

I use PixInsight.

Hope you are all doing well.

[vlazg (George)]

Hi David, have a look at this.
https://jonrista.com/the-astrophotog...e/pixinsights/
George

[sil (Steve)]

I find it best to make a range mask from a range mask from a range mask. Not a single range mask in one go from the image, usually takes a few iterations to separate out the things I want from what I dont. Play with smoothness to get rid of most "noise" I can't think why you want such a binary mask.

[DavidS (David)]

Hi George - thanks for the link to the tutorials. I'll go through these as they are not ones I have seen before.

Hey sil, the reason for this mask is I am following a tutorial in Warren Keller's book, Inside PixInsight, and in the example workflow he builds a range mask around a nebula, Binarizes it, applies convolution to soften the edges around the nebula and then subtracts a star mask. When it is inverted you can then bring out the colour etc in the nebula and protect the stars in front of the nebula. But the star mask I had was way too noisy and hence affecting the background.

Thanks for the idea of a recursive range mask. I'll also give that a go.
David

[sil (Steve)]

Have you reached as far as you can with the ranges to remove the noise? Or stopped because you were losing nebulosity? You can export your range mask as a tiff and edit it elsewhere (eg photoshop) if no choice by thats ugly too. Another approach could be take your source image and give it a 2 to 3 pixel gaussian blur to kill most of the noise, and use that to create your range mask from. Of course you use that rangemask on your original image for processing but the mask is never critical to be pixel perfect directly from the original. Likewise your star mask can be generated from a blurred original too, detail doesn't matter and the star mask can be tricky to get the stars right too. Getting the two masks to match together tends to be difficult, I prefer removing the stars completely leaving background/nebulosity to boost and adding the stars back later. Good luck with the book.