Star size reduction in PS

[gonzostar]

Hi, i'm currently trying to work on NGC 6960 however the star 52-Cyg wants to be center of attention. Was wondering if there was away of reducing star size in photoshop

I've inserted a quick image. This is only 4hours of data using a ZWO 385MC camera each pic was 120s with a gain of135

Thanks

Dean

[ollypenrice]

First make a copy layer of the starting point image.

Next create a feathered eraser to remove the top layer around the big star. In this screen grab the bottom layer has been made invisible so you can see the range of the eraser. However, the bottom layer is still the same as the top layer if rendered visible.

Next, make both layers visible and make the bottom layer active. Open Curves. Alt click on the background sky just outside the star bloat. This will produce the middle point you see on the curve below. Place a fixing point on the curve below that. Now grab the curve above the two fixing points and pull it down to reduce the bloat. Flatten the image and repeat if necessary. Do not aim for a perfect large star in one iteration. Be patient. Few things in life are as perfect as Photoshop.

Olly

[symmetal]

There are some star reduction actions for PS like 'Astronomy Tools 1.6', 'Steve's Astro Actions', and 'Star Reduction Bill Blanshan Method', but they work on smaller 'defined' stars rather than coloured halos. 

In this case I think it's best just to neutralise the halo colour using either method below.

1) Make a copy of your image layer (Ctrl-J) and Use Hue/Saturation to make the copy monochrome. Add an empty (black) layer mask by holding down the 'Alt' key while adding layer mask. Mono layer disappears. Select white as your main paint colour and select a very soft edge small brush with about 25% opacity. Select the black layer mask and keep dabbing the brush over the star halo until the mono star appears as much as you want it to neutralise the colour.

2) A more versatile way depending on what you want to do with halos is the defringe section of Camera raw Filter. Very useful for bloated blue halos where you likely won't need to mask the image or Channel Mix it as I've done below.

In your case to use the 'Defringe' section of the 'Camera Raw Filter' in the 'Filters menu'. However it only works on mainly Blue/Purple or Greenish fringes. So swap the red and blue channels over in your image.

A quick way of doing this is using the Image/Adjustments/Channel Mixer and make the red channel only 100% blue and the blue channel only 100% red.

Draw a circular mask around the outer edge of the offending star and then use Select/Modify/Feather to smooth the edge of the mask. 5 pixels of more should be OK.

Select the Filters/Camera raw filter, scroll down to defringe, click on the eyedropper tool and click over the darkest blue fringe on the offending star This will neutralise the star blue fringe making it less obtrusive. You can play with the sliders under the eyedropper to modify how much you affect the fringe colour.

Exit camera raw, remove the mask, and use Channel Mixer to reverse the Red and Blue channel swap you did above. Here's the result

 

A bit overkill in your case but just an example of defringing. 🙂 Not reduced in size but less jarring than the original.

Alan

[carastro]

Oh wow Olly that's a great tip, I just tried that on Rigel (witch Head), amazing.

Tip saved (as usual).

Carole 

[AstroMuni]

Do these techniques mentioned above work even with images taken with Newts?

I would love to reduce the flare around the same star in my version taken on Sunday. Please ignore the other defects in this image. Its only 1hrs worth of data captured with just a UV/IR filter and I know I have coma issues too.

 

 

Edited July 16 by AstroMuni

[gonzostar]

23 hours ago, ollypenrice said:

First make a copy layer of the starting point image.

Next create a feathered eraser to remove the top layer around the big star. In this screen grab the bottom layer has been made invisible so you can see the range of the eraser. However, the bottom layer is still the same as the top layer if rendered visible.

Next, make both layers visible and make the bottom layer active. Open Curves. Alt click on the background sky just outside the star bloat. This will produce the middle point you see on the curve below. Place a fixing point on the curve below that. Now grab the curve above the two fixing points and pull it down to reduce the bloat. Flatten the image and repeat if necessary. Do not aim for a perfect large star in one iteration. Be patient. Few things in life are as perfect as Photoshop.

Olly

Thankyou Olly, for taking your time and effort to show me this. I see what you mean by repeating procedure. Will add more integration time to this  image. Now I'm armed and a bit more practice I could attempt to take on Alnitak in a few months time 

Cheers

Dean

[gonzostar]

23 hours ago, symmetal said:

There are some star reduction actions for PS like 'Astronomy Tools 1.6', 'Steve's Astro Actions', and 'Star Reduction Bill Blanshan Method', but they work on smaller 'defined' stars rather than coloured halos. 

In this case I think it's best just to neutralise the halo colour using either method below.

1) Make a copy of your image layer (Ctrl-J) and Use Hue/Saturation to make the copy monochrome. Add an empty (black) layer mask by holding down the 'Alt' key while adding layer mask. Mono layer disappears. Select white as your main paint colour and select a very soft edge small brush with about 25% opacity. Select the black layer mask and keep dabbing the brush over the star halo until the mono star appears as much as you want it to neutralise the colour.

2) A more versatile way depending on what you want to do with halos is the defringe section of Camera raw Filter. Very useful for bloated blue halos where you likely won't need to mask the image or Channel Mix it as I've done below.

In your case to use the 'Defringe' section of the 'Camera Raw Filter' in the 'Filters menu'. However it only works on mainly Blue/Purple or Greenish fringes. So swap the red and blue channels over in your image.

A quick way of doing this is using the Image/Adjustments/Channel Mixer and make the red channel only 100% blue and the blue channel only 100% red.

Draw a circular mask around the outer edge of the offending star and then use Select/Modify/Feather to smooth the edge of the mask. 5 pixels of more should be OK.

Select the Filters/Camera raw filter, scroll down to defringe, click on the eyedropper tool and click over the darkest blue fringe on the offending star This will neutralise the star blue fringe making it less obtrusive. You can play with the sliders under the eyedropper to modify how much you affect the fringe colour.

Exit camera raw, remove the mask, and use Channel Mixer to reverse the Red and Blue channel swap you did above. Here's the result

 

A bit overkill in your case but just an example of defringing. 🙂 Not reduced in size but less jarring than the original.

Alan

Thankyou Alan for taking your time and effort to show this. Liking how the halo has gone. This is the aims. Struggling to find  the defringe section in filters rawfilters section  though. 

Cheers

Dean

[symmetal]

Hi Dean,

Glad to help.  🙂 What version of PS are you using. The camera raw filter has had many additional features with later versions and defringe wasn't available in earlier versions I believe. I'm using the latest PS CC version. Here's the defringe section in the latest Camera Raw Filter

Alan

[gonzostar]

Unfortunately I'm using the CS6 version. May have to get astronomy tools for PS

[symmetal]

3 hours ago, AstroMuni said:

I would love to reduce the flare around the same star in my version taken on Sunday. Please ignore the other defects in this image. Its only 1hrs worth of data captured with just a UV/IR filter and I know I have coma issues too.

Here's the Camera Raw Filter defringe applied to your image. Instead of swapping the red and blue channels I just inverted the image (colour wise) with Ctr-I, to make the yellow flares blue and applied defringe twice selecting the dark and the light (now blue) flares, applied to the whole image rather than masking the stars. The yellow tinges in the nebula and background have also been reduced as a result without affecting the red and blue in the nebula very much. Repeated defringing selecting the (now blue) tinges on the background may help too though there comes a point where the defringe can't find enough colour difference to work.

Alan

[symmetal]

55 minutes ago, gonzostar said:

Unfortunately I'm using the CS6 version. May have to get astronomy tools for PS

I don't think Astronomy Tools has an action that does what you want here, but is worth getting anyway as it doesn't cost a lot for what it can do.

Have you tried selecting Updates in your Photoshop version. Camera Raw seems to be treated as a separate item, distinct from Photoshop, so there may be a later version available that works with CS6.

Alan

[Xiga]

Don't overlook the Liquify filter in PS either. When you open the filter, you just need to select the Pucker tool from the left hand panel, then change the tool size (using the square brackets keys) so it extends beyond the outer halo, then carefully click the centre of the star a few times until you are happy with the amount of reduction. 

I just did a quick go myself (i'm using PS CC 2019) using a combination of some of the methods above and the Liquify filter. I made a copy of the layer, then used the Hue/Saturation filter to remove most of the colour from the layer (although you could also use the Defringe tool in Camera Raw just as well). Then I applied a black layer mask, and used a soft white brush to punch a soft hole through the mask around the star. Then i used the Liquify filter on the star, and finally used a curve similar to what Olly used above, just to darken the outer halo and bring the glow around the star down to something closer to the rest of the image.