Star Xterminator workflow.

[ollypenrice]

I wrote this Photoshop workflow down for guests and thought I'd post it here as well. This is my current StarXterminator workflow, though it's not set in stone and owes much to Ciaran here on SGL.

Star Xterminator

1 Log stretch the image to about 80% of full stretch and set the black point not too dark. Save as Stretch1.

2 Run StarX. Save as Starless. Process Starless as you see fit. I use Noise Xterminator as a bottom layer and erase the bright, sharp bits which don’t need it. I also fix the background and stretch a little more above that, using Curves. Do all contrast enhancement and sharpening to the starless image. Save.

3 Paste Starless over Stretch I. From here on I have made an Action:

4 Ctrl I to invert both layers.

5 Top layer active, set blend mode to Divide.

6 Stamp down. (Alt Ctrl E) This gives a new top layer.

7 Ctrl I to invert that layer.

8 Flatten image. (Do this under the layers palette from the top toolbar. Ctrl E does not work for me.)

9 Save as Stars. End action.

10 Paste Stars onto the processed Starless, blend mode screen.

11 Use Levels mid-point slider to reduce stars. 

12 Small stars benefit from contrast reduction. (Just the basic Image-Adjustments-Brightness and contrast from the toolbar.) Large soft stars benefit from contrast increase. Usually there are only a few large soft stars so I lasso them, increase contrast, then invert the selection and reduce contrast to soften small, hard pointy stars. Another way to soften them is to give a touch of Gaussian blur or to reduce the opacity of the star layer by a tiny amount.  Stars which still stand out un-naturally against nebulosity can be settled into the image by giving the starless layer a dab with the burn tool right under the star to restore a bit of stellar 'glow.'

Olly

[tooth_dr]

2 hours ago, ollypenrice said:

Log stretch the image to about 80% of full stretch

Thanks for sharing this workflow Olly.

I'm not 100% what this means though, done using curves? and how do you know what 80% is?  Thanks

[ollypenrice]

1 hour ago, tooth_dr said:

Thanks for sharing this workflow Olly.

I'm not 100% what this means though, done using curves? and how do you know what 80% is?  Thanks

80% is just a rough guess as to how much more stretching an image is likely to take. Basically I give it the StarX treatment when I think I'm nearly but not quite fully stretched. It's flexible. It's easier to judge the fully full stretch with the stars out of the way.

Then, rather than stretch the background beyond its final ideal brightness, I prefer to go from Levels into Curves, pin the background where it is (Alt click on a bit of background) put a fixing point below that and stretch above it.

This example has made an unholy mess of the image but I'm just explaining the method.  In many stretching tutorials the imager stays in Levels and continues to stretch, taking the background too high and bringing it back down by moving in the black point. I can see no reason to do this because you are just lifting the background above the noise floor.

You do need to be careful, when stretching only above the background, not to create an artificial step in the transition from background to faint stuff. To avoid this I'm very careful when choosing my background sample and I do a lot of small lifts rather than one big one.

Olly

 

 

[tooth_dr]

12 minutes ago, ollypenrice said:

80% is just a rough guess as to how much more stretching an image is likely to take. Basically I give it the StarX treatment when I think I'm nearly but not quite fully stretched. It's flexible. It's easier to judge the fully full stretch with the stars out of the way.

Then, rather than stretch the background beyond its final ideal brightness, I prefer to go from Levels into Curves, pin the background where it is (Alt click on a bit of background) put a fixing point below that and stretch above it.

This example has made an unholy mess of the image but I'm just explaining the method.  In many stretching tutorials the imager stays in Levels and continues to stretch, taking the background too high and bringing it back down by moving in the black point. I can see no reason to do this because you are just lifting the background above the noise floor.

You do need to be careful, when stretching only above the background, not to create an artificial step in the transition from background to faint stuff. To avoid this I'm very careful when choosing my background sample and I do a lot of small lifts rather than one big one.

Olly

 

 

Thanks Olly.  Very useful thanks  

[carastro]

Thanks Olly once again for your useful workflow tips.  I don;t have Star Exterminator (PC not up to is), but I am sure the workflow can be applied to whatever other method I use.

Your "Exploiting the Equalise Function" tutorial gets a fair bit of use with fainter tagets.

Carole 

[windjammer]

 >> "Exploiting the Equalise Function" tutorial 

Do you have a link for that BTW ?

Simon