I made a Photoshop Action for Bill Blanshan's new Star Reduction Method based on Pixel Math

[Xiga]

Hi guys

After seeing Bill's amazing new method for doing star reduction using Pixel Math in PixInsight, i immediately knew i wanted to make a Photoshop Action that effectively did the same thing, because not everyone owns (or enjoys using!) Pixinsight. I've attached the PS action below. Please feel free to experiment with it and post your results so i can see how it works out for other data sets. Essentially, it is by far the best method of doing star reduction i've come across so far, as it uses a lesser-stretched version of the original image to reduce the stars, which means you won't end up with any artefacts at all. 

First things first, a big shout out to lukomatico on Youtube, which is where i first saw this. Regardless of whether or not you're a PI or PS user, I definitely recommend checking out the video below, where Bill explains the process very well. 

https://www.youtube.com/watch?v=rM3-yAcAbZc&t=178s&ab_channel=lukomatico

 

Ok so to make this work, there are a few caveats. Namely:

1. You will need a starless image. No big deal these days hopefully, now that we have StarnetV2 and StarXTerminator available. 

2. Make sure the original image (with stars) you are working from is a standalone file that's been flattened. In other words, don't just copy and paste a layer from another image into a new image and flatten. This seems to break the action. I will try and fix this if i can! 

3. Don't process the original image or starless image in any way before trying this. They must be the same image, apart from the stars being removed, for this to work best.

4. The original image with stars must be sitting on the bottom as the Background Layer, and the Starless layer must be sitting on top as 'Layer 1'. Don't rename the layer, and make sure both layers are visible (using the little Eye icon on each one). Basically, if you just open the original flattened image and paste on top the starless image, you should be good to go. Sorry, i don't really have any advanced Photoshop skills in terms of making actions that are impossible to break! But i can confirm if you follow these instructions to the letter, then they will definitely work! 🙂 

So you're workflow should look exactly as such:

Then just run the action, and it will do it's thing up until the point where we need to apply a Curves adjustment to set the amount of star reduction needed. The action will pause at this point, and you should now see a Curves Adjustment Layer on the right hand side panel with a suggested curve (just my own idea as a starting point, feel free to try different ones!). Once you're happy with the level of stretch, press Play again on the action to finish it. Note, a too aggressive curve may result in the stars having too harsh an edge to them, or even some halos around them. I strongly recommend a one-point curve to keep the stars as natural looking as possible. Also, in extreme cases you may get better results by running the whole thing more than once, with a less aggressive stretch. In which case, you will need a new starless image each time. So far, i've only tested this on a single Lum data set of my own, and one pass was enough for my own needs (see example below). Of course, depending on your own equipment YMMV. 

Here is the PS action:

Star Reduction Bill Blanshan Method.atn

And here is a quick before and after animation of a WIP Lum stack of the Cocoon Nebula i took last week with my 80ed, using the default settings above. Note, this is with a cheap SVBony Lum filter, which i really need to replace due to excessive bloating. No fancy processing here, just a DDP stretch straight out of APP, then a pass of Noise-XTerminator, before doing the star reduction. This is a 100% crop of a portion of the image. Another benefit of this method that i've found, is that it doesn't affect the background at all, so any faint dust that is residing in the background doesn't get reduced at all:

Really interested to see how it holds up with other data sets, and also with other curve adjustments, as the amount of star reduction one likes is often down to personal taste. 

ps - Not sure if this is actually the best place to post this, so Mods feel free to move if needs be. 

🙂 

Edited October 26, 2022 by Xiga

[Laurieast]

It keeps telling me this?

[Shibby]

Just tried this and it's worked quite nicely for me, I think! I've only given it a very quick test with an existing, fully processed, fairly poor image. My results are below.

Thanks very much for the action!

 

[Xiga]

1 hour ago, Laurieast said:

It keeps telling me this?

Hi Laurence

I don't recognise the layers in your image above. It looks like you have selected a different Action above, called 'Star Mask'. Are you sure you didn't accidentally run this action instead? 

[Xiga]

30 minutes ago, Shibby said:

Just tried this and it's worked quite nicely for me, I think! I've only given it a very quick test with an existing, fully processed, fairly poor image. My results are below.

Thanks very much for the action!

 

Very good Lewis! I also think using it near the end of a workflow is the way to go. 

Nice Cocoon btw! 👌

[Laurieast]

30 minutes ago, Xiga said:

I don't recognise the layers in your image above. It looks like you have selected a different Action above, called 'Star Mask'. Are you sure you didn't accidentally run this action instead? 

Yes, I have run the wrong action, sorry! 🤦‍♂️

But I  am not seeing your action in the actions window, I put it in the plugins folder. I expect I'm doing something completely wrong. Where should it go? 

Thanks!

[Xiga]

11 minutes ago, Laurieast said:

Yes, I have run the wrong action, sorry! 🤦‍♂️

But I  am not seeing your action in the actions window, I put it in the plugins folder. I expect I'm doing something completely wrong. Where should it go? 

Thanks!

Did you restart Photoshop after copying the action into the plugins folder? I'm pretty sure you need to close it down and reopen.

Also, if you're not sure which exact folder to put it in, just find the folder where your existing actions are saved and put it in there (sorry, I'm at work so I can't check the exact folder on my own version until later). 

Edited August 23, 2022 by Xiga

[Laurieast]

1 hour ago, Xiga said:

Did you restart Photoshop after copying the action into the plugins folder? I'm pretty sure you need to close it down and reopen.

A Re-boot fixed it, or because I did a search within CS6 for atn, found yours clicked it and it appeared in PS, who knows!

Now to try it 😀

Edit: Works a treat, used your image above. Great!!

Thanks for the action!

Edited August 23, 2022 by Laurieast

[Xiga]

9 hours ago, Laurieast said:

A Re-boot fixed it, or because I did a search within CS6 for atn, found yours clicked it and it appeared in PS, who knows!

Now to try it 😀

Edit: Works a treat, used your image above. Great!!

Thanks for the action!

Excellent. Glad you got it working! 🙂 

[Felias]

Thank you! This could be very useful for us PS users.... but I couldn't make it work. It keeps telling me "The command 'duplicate' is not currently available" , "The command 'invert' is not currently available", and "The command 'select' is not currently available". Any idea what's going on? I'm using the last version, PS 2022,and I'm quite sure that I set the layers as instructed. 🤔

 

Edited August 23, 2022 by Felias

[Xiga]

7 minutes ago, Felias said:

Thank you! This could be very useful for us PS users.... but I couldn't make it work. It keeps telling me "The command 'duplicate' is not currently available" , "The command 'invert' is not currently available", and "The command 'select' is not currently available". Any idea what's going on? I'm using the last version, PS 2022,and I'm quite sure that I set the layers as instructed. 🤔

 

Hmm, that is odd. Why is the Crop tool visible in the picture above? 

Did you have anything copied to the clipboard before you ran the action? 

[Chris-h]

Yeah, I got the same thing. I am using CS6

[Felias]

5 minutes ago, Xiga said:

Hmm, that is odd. Why is the Crop tool visible in the picture above? 

Did you have anything copied to the clipboard before you ran the action? 

Well, the crop tool is selected because I was cropping a photo before, and never changed it. I have tried selecting another tool, and I still get the same message. I did copy the starless image and pasted it as a new layer, yes -will that make a difference?

Oddly enough, I have performed manually the steps that the action refuses to do, and once I get past them, it works until it stops at the 'curves' action. Is there a curves window meant to pop up at this step? If I keep running the action, I get a final photo with too much reduction, it needs tweaking. But I tried to run curves myself, and it did not seem to affect the mask on screen, so I was blind to what I was doing.

[Xiga]

Hmm, i'll have a play around with it myself later and see if i can get a similar error message. Although i'm struggling to think of what would prevent PS from duplicating a layer. 

Yes, the action stops at the 'Curves' stage and a message box is supposed to pop-up with some notes. Also, the Curve is a Curves Adjustment Layer, so the settings should be on the right hand side panel somewhere, where you can adjust it yourself. If you find it's a bit high then just bring down the curve a bit and then press Play one more tie on the Action to finish it. 

Thanks for the feedback so far guys! 

[Felias]

6 minutes ago, Xiga said:

Hmm, i'll have a play around with it myself later and see if i can get a similar error message. Although i'm struggling to think of what would prevent PS from duplicating a layer. 

Yes, the action stops at the 'Curves' stage and a message box is supposed to pop-up with some notes. Also, the Curve is a Curves Adjustment Layer, so the settings should be on the right hand side panel somewhere, where you can adjust it yourself. If you find it's a bit high then just bring down the curve a bit and then press Play one more tie on the Action to finish it. 

Thanks for the feedback so far guys! 

I have made it work! The problem seems to be that I was copying the background from a layer of my previous processing, into a new file. PS does not seem to recognise it as the background even if you put it at the bottom and lock it. If you open it from a saved file and just add the starless image as a layer, it works! And yes, the curves were there to the right, as usual, I don't know why I didn't see them before. 

Very useful tool indeed, thank you!

[Xiga]

14 minutes ago, Felias said:

I have made it work! The problem seems to be that I was copying the background from a layer of my previous processing, into a new file. PS does not seem to recognise it as the background even if you put it at the bottom and lock it. If you open it from a saved file and just add the starless image as a layer, it works! And yes, the curves were there to the right, as usual, I don't know why I didn't see them before. 

Very useful tool indeed, thank you!

Brilliant, glad it's working now! And thanks for the feedback too. I'd like to fix that, although i'm not quite sure how tbh. If i find a way to make it a bit more robust i'll post up an updated version. 

ps - Care to share a before and after pic of the star reduction? 

Edited August 23, 2022 by Xiga

[Felias]

I have tried it with a photo I took back in July, which I have been reprocessing today, and it works really well. It's a WO Z61, so about 400 mm focal length. The reduction seems fine for both small and large stars, even considering that they are not perfectly round because there's always some trailing with my Star Adventurer.