Using Heal to process stars and background independently

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Using Heal to process stars and background independently

Postby admin » Thu Dec 06, 2012 10:17 pm

Let's say we have this image here;
Miquel_Heart_PreLife_Post2_crop.jpg
Miquel_Heart_PreLife_Post2_crop.jpg (58.82 KiB) Viewed 5952 times


Let's create a star mask that Heal can use to heal out the stars; (Mask, Auto, Stars, set 'Exclude Color' to 'Red' so that it won't select much of the nebula);

img_129.png
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Now run the Heal module, but make sure you set 'New darker than old' to 'Yes'. What this does is guarantee that replacement pixels for the stars are always darker than the stars themselves;

img_130.png
img_130.png (331.95 KiB) Viewed 5952 times


'Keep' the result and save the healed image for future reference. Now reset the mask (Clear, Invert) and launch the Layer module.
In the Layer module, click Undo->Bg. This will set the background to what's in the undo buffer (which is the original image).
Now set Layer Mode to 'Subtract' and voilà! We have perfectly extracted the stars;

img_131.png
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Save the star field - we'll need it later to layer it back in.
Click 'Undo' to restore the background-only image.
Now let's have some fun with the background!
For example, let's do some wavelet sharpening of the larger scale details;

img_132.png
img_132.png (350.42 KiB) Viewed 5952 times


There's plenty more we could do (Life, Wavlet Denoise, HDR, etc.) but for the purpose of this demo this is enough.
Once we're happy with our new background, all we need to do now is layer the stars back in.
Launch the Layer module, click Open, locate and load the stars-only image.
All we need to do now is simply 'Add' the stars back to the background. And Bob's our (proverbial) uncle!

img_133.png
img_133.png (706.96 KiB) Viewed 5952 times


Note that stars may be slightly blow out in places where nebula+starlight exceeds unity (= pure white). This should be fairly minimal, but if that is a concern to you, set 'Cap Mode' to 'Normalize'.

Miquel_Heart_PreLife_Post2_crop_bg_new.jpg
Miquel_Heart_PreLife_Post2_crop_bg_new.jpg (60.56 KiB) Viewed 5952 times
Ivo Jager
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Re: Using Heal to process stars and background independently

Postby mcbbcn » Fri Dec 07, 2012 12:08 am

Very awesome! Now, we have a great chance to accentuate those stars without over saturating the whole image. Thanks for putting together this guide! :bow-yellow:
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Re: Using Heal to process stars and background independently

Postby torsinadoc » Thu Dec 05, 2013 7:04 pm

very nice. Just tried it. I really like the ability to separate the stars on wide field views
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Re: Using Heal to process stars and background independently

Postby mcbbcn » Thu Dec 05, 2013 8:38 pm

torsinadoc wrote:very nice. Just tried it. I really like the ability to separate the stars on wide field views
Yes, it's a fantastic tool! :obscene-drinkingcheers:
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Re: Using Heal to process stars and background independently

Postby Cheman » Thu Dec 05, 2013 8:58 pm

Awesome. I will print this out and add it to my Startools how to binder. I really like these step by step instructions. Easier to follow for me than the vids. Keep 'em comming.
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Re: Using Heal to process stars and background independently

Postby akeru » Sun Mar 02, 2014 8:01 pm

Hi all. Heal is a very powerfull function but I have a question. Why heal is unavailable with the tracking enabled?
And if I work with heal due to separate stars and nebula and later I add the different layers in a only image again ¿Must I activate tracking again? It had impact in the noise reduction process?

Thanks a lot.

Roberto.
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Re: Using Heal to process stars and background independently

Postby admin » Sun Mar 02, 2014 8:21 pm

akeru wrote:Hi all. Heal is a very powerfull function but I have a question. Why heal is unavailable with the tracking enabled?
And if I work with heal due to separate stars and nebula and later I add the different layers in a only image again ¿Must I activate tracking again? It had impact in the noise reduction process?

Thanks a lot.

Roberto.


Yes, you're right. Heal (along with a couple of other modules) is unavailable while Tracking is enabled as it will (presently) greatly interfere with the continuous data analysis that Tracking performs. The reason for that is that Heal obviously 'makes up' data, for which no prior analysis exists (there is no record of its evolution). I have a fix for this, but it will require a fair bit of work (it's something for the next major release).

For the exact same reason, the Layer module will warn you to be very careful if Tracking is still on - it can make Tracking 'lose track' of signal evolution in your data.

Once Tracking is switched off, analysis is no longer possible, so, unfortunately, using Heal after switching Tracking back on will not help.
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