A New Way of Reducing Stars in Photoshop

[Xiga 1,682]

Hey guys

I know we all have our own favourite way of doing star reduction (i have used Noel Carboni's action, and i also like using the Minimum filter in PS too) but i think i may have stumbled across another new way, and i actually quite like it! The NC action tends to darken the image a bit, and it also doesn't seem to work well on extremely large stars, and the minimum filter does tend to soften the stars a bit (which can look quite nice, depending on the image) but this technique, if anything, actually seems to tighten up the stars, and you also get an Opacity slider to play with as well, so you can set as little or as much of it as you like. Also, the minimum filter tends to obliterate really small stars, whereas this method doesn't seem to at all, so depending on what you are trying to achieve this hopefully might prove useful to some. 

So here goes:

1. Create a 'Starless' version of your image. For this i use one of Annie's Actions and finish it off by using the Spot Healing Brush on any remaining star remnants. 

2. Put this Starless layer at the bottom and set the blend mode to Colour (the blend mode isn't critical here, especially if you've done the starless image carefully, but using Colour will always ensure you don’t lose any hard-earned detail).

3. Add your Master Luminance (or what you had as your pre-star-reduction image before) on top of the Starless layer. Then duplicate it so that you have 2 of them on top of the Starless layer. So 3 layers in total. 

4. Now change the Blend Mode of the Top layer to ‘Pin Light’.

5. Finally, bring down the Opacity of the Middle layer. 70% - 80% seems to work well, and can have quite a big impact, especially so on really big stars, but i wouldn't go any lower than this. 

 

I've shown a Before and After example below so you can see the effect. (apologies for the lack of resolution, it's from a very severe crop!) But i'd be really interested to see what others think of this, and whether or not the technique can be improved , or even if it's just to find out if it's actually no good at all! (i have no way of analysing images statistically, i simply rely on my own 2 eyes! lol). 

I know my way around PS pretty well these days (all thanks to AP) but it's basically all down to trial and error, so i don't consider myself an expert by any means. Just wanted to let people know that in advance! 

 

Edited December 9, 2017 by Xiga

[Xiga 1,682]

And here's a quick before and after M42 crop at 300%

Think this technique might be most useful on the really biggest brightest stars. 

ps - you really need to flick back and forth on the images, and not just view them side by side at the same time, to see the full effect

Edited December 9, 2017 by Xiga

[MarsG76 4,785]

Nice, thanks

 

[StargeezerTim 3,420]

Thanks...

I don't have Annies Actions, do you know of a good way of getting a starless layer? (Preferably idiot proof ) The only way I know is with the dust and scratches filter, but thats quite destructive to the image (unless it doesnt matter for this..).

Cheers  Tim.

Edited December 12, 2017 by StargeezerTim

[StargeezerTim 3,420]

I had a try on a galaxy image and it works well using dust and scratches to get a starless layer provided the galaxy is masked off. I actually went up to 60% without problems and you can also lower the fill slider a little. Works well, thanks.

 

If I could work out how to get a starless layer without affecting the DSO, it would be even better. More to learn!

[Xiga 1,682]

On 12/12/2017 at 18:37, StargeezerTim said:

Thanks...

I don't have Annies Actions, do you know of a good way of getting a starless layer? (Preferably idiot proof ) The only way I know is with the dust and scratches filter, but thats quite destructive to the image (unless it doesnt matter for this..).

Cheers  Tim.

Hi Tim

After playing around some more, it would appear that the starless layer at the bottom is not of paramount importance. But of course, you still want it to be as good as you can get it. I recommend Annie's Actions, they're not expensive, but i also have another source for a PS action to remove stars. I came across this one a while back, it's just a small action set made by a guy who offers it for free, and it includes actions to separate stars from sky background, i've attached the link below. I compared it to Annie's Action, and it doesn't do quite as good a job, as it doesn't really remove the big stars very well, but it still works quite well and it's certainly much better than having to do it from scratch.

http://troypiggo.blogspot.co.uk/2010/11/troys-astro-actions.html

I've also discovered that the blending mode of the starless layer makes no difference, so you can just leave it on Normal. The blend mode of the middle layer does matter, and needs to be kept on Normal (for info though, Luminosity, Lighten and Lighter Colour all work exactly the same too). But the top layer absolutely must be set to Pin Light. 

I'd be interested to see any before and after images that you try it on. 

[StargeezerTim 3,420]

10 hours ago, Xiga said:

Hi Tim

After playing around some more, it would appear that the starless layer at the bottom is not of paramount importance. But of course, you still want it to be as good as you can get it. I recommend Annie's Actions, they're not expensive, but i also have another source for a PS action to remove stars. I came across this one a while back, it's just a small action set made by a guy who offers it for free, and it includes actions to separate stars from sky background, i've attached the link below. I compared it to Annie's Action, and it doesn't do quite as good a job, as it doesn't really remove the big stars very well, but it still works quite well and it's certainly much better than having to do it from scratch.

http://troypiggo.blogspot.co.uk/2010/11/troys-astro-actions.html

I've also discovered that the blending mode of the starless layer makes no difference, so you can just leave it on Normal. The blend mode of the middle layer does matter, and needs to be kept on Normal (for info though, Luminosity, Lighten and Lighter Colour all work exactly the same too). But the top layer absolutely must be set to Pin Light. 

I'd be interested to see any before and after images that you try it on. 

Here is one with the layer at 75%. The galaxy is a little reduced in saturation, but nothing too great. The first is the original and the second the smaller stars version.

 

[Stub Mandrel 12,943]

Thanks for this, your results look good.

I looked at Annie's Actions but the website doesn't give a price it just tries to log you into paypal. I think this may be an error caused by an update so I've got in touch to suggest the price is put on the website!

[Filroden 1,412]

4 minutes ago, Stub Mandrel said:

Thanks for this, your results look good.

I looked at Annie's Actions but the website doesn't give a price it just tries to log you into paypal. I think this may be an error caused by an update so I've got in touch to suggest the price is put on the website!

It showed as $15 on the PayPal page.

[Xiga 1,682]

Did a little more playing around with this, and noticed something that i didn't before. The technique also seems to darken any extremely bright areas of nebulosity. I've shown a tight crop from an image below which shows what can happen, so care does need to be taken when using this method. FWIW, the image i'm working on at the moment didn't have too many areas that were affected, but i did have to use an extra layer and the eraser tool to clean up the affected areas.

ps - i don't know if it's just me, but i could swear that this method does also improve the sky background slightly too. I have been using it on DSLR Narrowband images, which are obviously noisier than most, so perhaps it's proving more helpful for that reason, but i do think that it darkens some low-level noisy pixels that are just a tad lighter than their neighbouring ones. I can't say for sure though! 

Edited December 16, 2017 by Xiga

[MartinB 2,578]

I'm a bit confused.  If the starless layer is at the bottom i.e. the background image you can't set a blend mode. Is the starless image on top of the background image?

 

[Xiga 1,682]

2 hours ago, MartinB said:

I'm a bit confused.  If the starless layer is at the bottom i.e. the background image you can't set a blend mode. Is the starless image on top of the background image?

 

The starless layer is definitely at the very bottom. But you're right that the blend mode for it doesn't matter, so you can just leave it on Normal.  Sorry if that wasn't clear! 

[MartinB 2,578]

Thank Clarin.  I think I must be doing something wrong here (not at unusual).  So a star obliterated colour image at the bottom.  A luminance on top of this - What are you using as the blend mode for this layer?

[StargeezerTim 3,420]

8 minutes ago, MartinB said:

Thank Clarin.  I think I must be doing something wrong here (not at unusual).  So a star obliterated colour image at the bottom.  A luminance on top of this - What are you using as the blend mode for this layer?

 I just used pin light for the top layer, no blend mode for the middle. Seemed to work for me...

[MartinB 2,578]

18 minutes ago, StargeezerTim said:

 I just used pin light for the top layer, no blend mode for the middle. Seemed to work for me...

I must be on the wrong wavelength here completely.  You can't have "no blend mode" except for the background layer.  The default is "normal" which would effectively block the background.  I suspect I'm missing something very obvious here!!

[StargeezerTim 3,420]

1 minute ago, MartinB said:

I must be on the wrong wavelength here completely.  You can't have "no blend mode" except for the background layer.  The default is "normal" which would effectively block the background.  I suspect I'm missing something very obvious here!!

Thats it. Normal for the middle layer. Adjusting its opacity applies the change.

[MartinB 2,578]

4 minutes ago, StargeezerTim said:

Thats it. Normal for the middle layer. Adjusting its opacity applies the change.

Is your middle picture an LRGB then, it can't be a luminance image?  I can make it work with an LRGB image although it does blur my galaxy a little

[StargeezerTim 3,420]

Martin, I've just done this on dslr one shot rgb images. I found it does lower the saturation of the galaxy a bit but if you mask the galaxy and apply it to the space it works well. I think the key is getting a good starless image. I tried deleting the stars with the 'colour range' 'highlights' so didn't need blur the background.

[carastro 8,761]

Quote

do you know of a good way of getting a starless layer? 

Straton will remove stars from Mono images, so you have to remove the stars of each channel.

I can see how the above would work with a narrowband image, but surely you are going to remove all the colour data from the stars of an LRGB image. 

Carole 

Edited December 17, 2017 by carastro

[Xiga 1,682]

Just to be clear, i have only been using this on OSC data, so the images have all been set to RGB mode in PS. 

There is no separate background layer. So when you create the starless image, it becomes the bottom layer. Then put on top 2 identical layers of the regular non-starless image. All 3 layers blend mode should be on Normal at this stage. The you just need to change the blend mode of the top layer to Pin Light. Finally, as Tim pointed out, you then need to adjust the opacity of the MIDDLE layer down a tad (e.g 60-80%). 

In addition, i don't think it does remove the colour data from stars. I don't have any especially high-quality RGB data to showcase this on, but i've shown a crop below from an old M33 image i did a year or so ago, which had some very large stars, and as far as i can tell it doesn't reduce the colour.

[SlimPaling 243]

On ‎09‎/‎12‎/‎2017 at 02:31, Xiga said:

So here goes:

1. Create a 'Starless' version of your image. For this i use one of Annie's Actions and finish it off by using the Spot Healing Brush on any remaining star remnants. 

Hi Xiga ...

Which one of "Annie's Actions" did you use?

I have had a look at her list on the web site and can't seem to spot the action that will remove the stars from the image.

If I can sort this out it will be a big help to me on occasions :-)

Mike

[Xiga 1,682]

29 minutes ago, SlimPaling said:

Hi Xiga ...

Which one of "Annie's Actions" did you use?

I have had a look at her list on the web site and can't seem to spot the action that will remove the stars from the image.

If I can sort this out it will be a big help to me on occasions :-)

Mike

Hi Mike 

The one I've been using is called Remove Stars (Large Image). 

Good luck! ?

[SlimPaling 243]

I must be blind !!!!

Thanks for pointing the way :-)

Mike

[Petergoodhew 1,738]

I've been really struggling with star reduction techniques messing up the stars. Have just tried this and it works a treat!  Many thanks.

[Rudy Pohl 162]

HI Xiga,

This is absolutely BRILLIANT! It worked first time for me and looks great! Thanks for sharing.

Cheers,
Rudy