StarXterminator/Photoshop 2022

[Fay]

Can anyone explain  after removing stars, with StarXterminator and Photoshop 2022,  and  processing nebula how do I put the stars back. It is not clear on the website and cant find any referance on how to recombine.

 

Thanks a lot, Fay

[ollypenrice]

This is my workflow. Do create a Photoshop Action as suggested below.

StarXterminator workflow in Photoshop.

1 Stretch standard image as usual to about 50% of final stretch. Simple stretch, nothing detailed. Save as Proc 1.

2 Run star Xterminator and save the starless image as Starless.

3 Continue to process Starless. Cosmetic repair of artifacts, harder stretch, contrast enhancement, noise reduction, sharpening, colour etc. Save. Select and copy.

4 Use Open Recent to re-open Proc 1 and paste Starless as a top layer.

5 Invert both layers.

6 Top layer active, change blend mode to divide.

7 Stamp down. (Alt Ctrl E)

8 Top layer active, Invert.

9 Flatten Image. (I seem to have to do this from the toolbar Layers dropdown because CtrlE doesn’t work.)

10 Save as Stars.

11 Select Copy

12 Paste onto Starless.

13 Blend mode to Screen.

 

Actions 5 to 9 inclusive can be recorded as a single action.

The stars can be reduced simply by lowering the mid point in Levels. Small stars can look too hard and can benefit from the simple contrast tool to reduce contrast. Large stars with halo or bloat benefit from an increase in contrast. Other possibilities include Gaussian blur or a reduction in top layer opacity by a tiny amount. Stars which look ‘stuck on’ over nebulosity can be made to settle into the image by means of a dab with the burn tool on the bottom layer, just underneath them.

 

Olly

Edit: I posted the above without realising it was you! How goes it?

Edited August 30, 2023 by ollypenrice

[ONIKKINEN]

Here is how i do it:

First i have stretched the image in Siril to a point where i think the stars are close to where i want them to be, but you could do it in any software of course (i do it in Siril because i do preprocessing there anyway).

1. Open the image in Photoshop and duplicate it twice to create 2 extra layers
2. Run StarXterminator on the top layer
3. Duplicate the starless layer once the process has completed and then hide the top starless layer.
4. Put the other, unhidden, starless layer into blend mode "subtract" and merge down.

Now i have a starless layer, a stars only layer, and the original image as background for comparison purposes mostly.

Once i have processed both layers the way i like i combine the starless and stars only layer using the blend mode "linear dodge(add)" and merge them. In my opinion simply adding the star layer back instead of screening the starless layer in front of it yields a more natural looking end result. With the blend mode set to screen you can end up with transparent looking stars, or stars that are hidden behind nebulosity. Entirely a matter of taste of course, and i think i may have the minority opinion here with preferring linear dodge over screening.

I have created a GIF of the difference between screening nebulosity in front of stars, and simply adding them:

The difference is barely noticeable outside nebulosity, but very easy to see for stars that are in front of nebulosity and appear to be muted with the blend mode set to screen.

[ollypenrice]

9 hours ago, ONIKKINEN said:

Here is how i do it:

First i have stretched the image in Siril to a point where i think the stars are close to where i want them to be, but you could do it in any software of course (i do it in Siril because i do preprocessing there anyway).

1. Open the image in Photoshop and duplicate it twice to create 2 extra layers
2. Run StarXterminator on the top layer
3. Duplicate the starless layer once the process has completed and then hide the top starless layer.
4. Put the other, unhidden, starless layer into blend mode "subtract" and merge down.

Now i have a starless layer, a stars only layer, and the original image as background for comparison purposes mostly.

Once i have processed both layers the way i like i combine the starless and stars only layer using the blend mode "linear dodge(add)" and merge them. In my opinion simply adding the star layer back instead of screening the starless layer in front of it yields a more natural looking end result. With the blend mode set to screen you can end up with transparent looking stars, or stars that are hidden behind nebulosity. Entirely a matter of taste of course, and i think i may have the minority opinion here with preferring linear dodge over screening.

I have created a GIF of the difference between screening nebulosity in front of stars, and simply adding them:

The difference is barely noticeable outside nebulosity, but very easy to see for stars that are in front of nebulosity and appear to be muted with the blend mode set to screen.

Interesting. I've encountered the problem of stars not showing well against nebulosity and tackled it by using Colour Select to select the nebulosity and giving that selection a slightly boosted stretch on the star layer. I'll try your method.

Olly

[gorann]

You can also just follow the instruction made by the Russ Croman, the creator of Star XTerminatror:

https://www.rc-astro.com/starxterminator-usage-notes/

I use the Photoshop action he gives out (click one "here" at the end of his instruction). In one step it creates three layers: Background, Starless and Stars. I use that action rather than doing it "manually".

 

[Fay]

Thanks for all your help. I saw that I could make an Action but it said it will not work with my version of PS. 2023

 

Fay

[gorann]

21 hours ago, Fay said:

Thanks for all your help. I saw that I could make an Action but it said it will not work with my version of PS. 2023

 

Fay

I see. Mine is PS 2021. Hopefully Russ will update the action.