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Using Heal to process stars and background independently

Posted: Thu Dec 06, 2012 10:17 pm
by admin
Let's say we have this image here;
Miquel_Heart_PreLife_Post2_crop.jpg
Miquel_Heart_PreLife_Post2_crop.jpg (58.82 KiB) Viewed 34680 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
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'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
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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
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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 34680 times

Re: Using Heal to process stars and background independently

Posted: Fri Dec 07, 2012 12:08 am
by mcbbcn
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:

Re: Using Heal to process stars and background independently

Posted: Thu Dec 05, 2013 7:04 pm
by torsinadoc
very nice. Just tried it. I really like the ability to separate the stars on wide field views

Re: Using Heal to process stars and background independently

Posted: Thu Dec 05, 2013 8:38 pm
by mcbbcn
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:

Re: Using Heal to process stars and background independently

Posted: Thu Dec 05, 2013 8:58 pm
by Cheman
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.
Che

Re: Using Heal to process stars and background independently

Posted: Sun Mar 02, 2014 8:01 pm
by akeru
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.

Re: Using Heal to process stars and background independently

Posted: Sun Mar 02, 2014 8:21 pm
by admin
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.

Re: Using Heal to process stars and background independently

Posted: Sun Oct 28, 2018 4:53 pm
by Burly
lost me here ivo save to where how?- Save the star field - we'll need it later to layer it back in.

Re: Using Heal to process stars and background independently

Posted: Mon Oct 29, 2018 2:56 am
by Rkonrad
Hi Dave,

I've made a quick video. Does this make more sense to you? https://youtu.be/x2tBFwt-SeM

Cheers Richard

Re: Using Heal to process stars and background independently

Posted: Mon Nov 05, 2018 1:14 pm
by Burly
Rkonrad wrote:Hi Dave,

I've made a quick video. Does this make more sense to you? https://youtu.be/x2tBFwt-SeM

Cheers Richard
Thanks Richard I will take a look of that this evening