dead pixel (?) columns wipe doesn't do anything?

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dead pixel (?) columns wipe doesn't do anything?

Postby jeffpadell » Mon Nov 25, 2019 10:33 pm

The camera on the 17" scope at Slooh has a white line in every capture (FITS). It appears a a bright white line, not sure what exactly it is, dead pixels or what

BUT the question is, I can get rid of it in Photoshop with the healing brush or the stamp tool, but I thought that Star Tools Wipe tool could get rid of it, but I created a mask and used every part of the Wipe tool to try to get rid of but nothing worked. I was told that Pixinsight handles this fine BUT I am on Social Security as my sole income and the $250 cost for it is currently out of my reach, although a friend of mine said that there is nothing wrong with seeing the cord below the treads on my tires and that if I only eat one meal a day I can save money for it and he said I can stand to miss a few meals (ROFL)

Does anyone have an idea how to do this in Star Tools?

I am just learning how to use Star Tools, I have been using Nebulosity 4 and fixing it in Photoshop

The picture below is just to show the problem it is only 1 L,R,G,B and a 2 1/2 minute exposure only stretched with no other processing

Image
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Re: dead pixel (?) columns wipe doesn't do anything?

Postby admin » Tue Nov 26, 2019 1:06 am

Hi,

This is indeed a defective pixel column showing hot pixels.
However, Wipe does not deal with such cosmetic defects; it only deals with gradients, light pollution bias, etc.
Masking in Wipe is only meant to make Wipe "blind" to certain artefacts (dark anomalies, as opposed to a bright anomaly like this) that may cause it locally back off.
In short, Wipe is not the tool for the job (and I would urge you to read up what is Wipe's job).

The tool you're looking for is the Heal module (NOTE: not available while Tracking is on).

Its job is simple; heal out all pixels set in the mask in a neutral manner.

So first order of business is to create a mask. The Auto mask generator can actually detect artefacts like these quite well.
StarTools_104.png
StarTools_104.png (574.46 KiB) Viewed 213 times


After that, i grew (Grow button) the mask a little, purely because of the JPEG artifacts that surrounded the defective column. I also deselected any stars in the mask.
Final mask here (you can import this mask as well if you want);
qSPUaSdl_mask.jpg
qSPUaSdl_mask.jpg (16.86 KiB) Viewed 213 times

The, launch (or return to) the Heal module, which will now Heal precisely the pixels selected in the mask;
qSPUaSdl_healed.jpg
qSPUaSdl_healed.jpg (80.55 KiB) Viewed 213 times


Incidentally, your friend is incorrect about PixInsight; it does not allow for precise mask editing and healing in this way, as it is considered "doctoring" by the authors. We make no such judgements, but would like to point out that the "proper" way for dealing with such defectc is to dither between frames (e.g. during acquisition), then stack those frames, rather than fixing this in post-processing. The rejection algorithm used during stacking will reject the outliers and the artifact will disappear entirely from the dataset.

Hope this helps!
Ivo Jager
StarTools creator and astronomy enthusiast
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Re: dead pixel (?) columns wipe doesn't do anything?

Postby jeffpadell » Tue Nov 26, 2019 3:31 pm

Ivo
Thank you very much for the help. I have been using the remote scopes with Slooh and find it complicated and a pain to set up additional sessions to dither. I usually use the heal brush in Photoshop but am starting to learn Star Tools as it is a very good program
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