Processing very dense starfields - any tips?

[MartinFransson]

Hi all!

I am trying to process a very dense starfield with very small stars and all my usual techniques fail! (starmasks with MultiscaleMedianTransform, Morpholigical Transformation)

The reason for the very dense starfield is that it´s shot with a Canon 50mm lens. So very wide field!

Is there a way to reduce or remove the stars to be able to process the darker parts separately? The methods I have tried so far work for larger stars and with longer focal lengths but fall short here...

[MartinFransson]

Gave it my best shot... but not fully satisfied. I want more separation of the dust clouds without the star overpowering the image.

[happy-kat]

What processing software are you using

[MartinFransson]

Pixinsight and Photoshop. 

[wimvb]

The target is right in the middle of the milky way. Stars are a natural phenomenon, which you wouldn't want to get rid of.

But if you want to reduce stars, it's all in a good starmask.

In the linear state:

Extract luminance and apply STF as a permanent stretch

Use this to create a star mask: Scale to 4, noise level to just below the value of the stars you want to include (use the pixel/screen reader tool).

Large scale to 0 to exclude larger stars. If you also want to affect larger stars, increase the large scale parameter, and also increase the Scale parameter

use Contours in mask generation and set Smoothness to 1. Try Compensation = 0 or 1

 

(values in the image are not for this recipe)

Tweak these values until you have a mask that fits the objective. The most important parameters to adjust are Noise threshold and Scale

You can use histogramtransformation to strengthen the mask. Then Convolution to blur it.

Apply the mask to the original image (invert to evaluate the mask, but apply normal for processing)

Morphological Transformation with Morphological Selection

Selection to 0.2

Amount to 0.5

Iterations to 4 - 5

Structuring Element, Size to 7 or 9, circular pattern

A contour mask with this MT usually makes stars considerably smaller and dimmer. But the largest brightest stars are preserved.

Hope this helps

 

[jezhughes]

Have you tried dust & scratches?

bit of a harsher way of doing it but it sure gets rid of stars.