Author Topic: How to remove hot pixels  (Read 5402 times)

Offline strivedi

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How to remove hot pixels
« on: 2013 November 30 13:03:52 »
I am still a newbie and learning PI. Recently I processed the Horsehead Nebula, but I do not know how to get rid of hot pixels.

The image can be viewed/downloaded at the link below:

https://www.dropbox.com/s/bb5dnbuv2544f75/HaLRGB_Final_Final.fit

Any tips or pointers are appreciated.

Shailesh Trivedi

Offline dgbarar

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Re: How to remove hot pixels
« Reply #1 on: 2013 November 30 14:47:58 »
Hi Shailesh,

Have you tried the bright pixel removal in cosmetic correction.

Cheers,

Don
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Offline Andres.Pozo

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Re: How to remove hot pixels
« Reply #2 on: 2013 December 01 02:34:58 »
Don is right and usually the CosmeticCorrection is the best way for removing hot pixels.

However the CosmeticCorrection tool is broken in the latest version of PI (v1.8.0.1054). If you have installed the previous version (1.8RC7), you shouldn't have problems since CC is ok in it.
http://pixinsight.com/forum/index.php?topic=6362.0

Offline strivedi

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Re: How to remove hot pixels
« Reply #3 on: 2013 December 01 14:47:30 »
I have the RC7 build, but for the life of me, I am unable to remove hot pixels using the Cosmetic Correction tool.

At what stage in the flow do you remove hot pixels? I have a fully processed FITs file. Using a master dark is the only way it will let me remove hot pixels, I am ok with that. When I click real time preview, I have to click twice to see the hot pixels removed - this is a bit strange.

Next when I clicks on the circle icon (to apply in global context), and save the _cc file, that file does not have hot pixels removed.

What am I missing? My build number is 1.08.00.1023 (x64) RC7

Shailesh

Offline StefanG

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Re: How to remove hot pixels
« Reply #4 on: 2013 December 02 13:05:00 »
The Cosmetic Correction Tools works nicely for me when I apply it on the individual subframes directly after image calibration. I think what is important is, that the master dark is reasonably current. Any hot pixel in the light that is not reflected in the master dark will not be removed. I have no experience with the real time preview in this tool. Does not seem to work for me...
But the Blink tools does the job very nicely.

I used this tool a lot with build RC7 so principally it should work. There are little problems with 1054.

Stefan
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Offline strivedi

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Re: How to remove hot pixels
« Reply #5 on: 2013 December 02 14:00:01 »
Thanks Stefan. What I was attempting to do is apply it to a fully processed HaRGB image and it did not quite work.

I will try individual subframes after calibration as you suggest.

Shailesh

Offline bitli

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Re: How to remove hot pixels
« Reply #6 on: 2013 December 03 03:46:42 »
Quote
I have no experience with the real time preview in this tool. Does not seem to work for me...
The RTP works fine and I find it useful. It is not intuitive how to use it. You may proceed as follow:
  • Load one of the files you want to correct in your workspace, you should probably apply STF
  • Preferably create a preview so that the RTP windows shows an image at zoom 1x or 2x  (in general hot pixels are distributed around the whole image, so any reasonably large preview with enough background will do)
  • Open the CosmeticCorrection tool when your image is selected
  • Start RTP, select the preview
Now you can enable/disable various hot pixel removal algorithms and see the effect on the preview (with a suitable STF).
May be there is a simpler way to persuade CC to show one of the image in RTP ?
-- bitli

Offline strivedi

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Re: How to remove hot pixels
« Reply #7 on: 2013 December 03 13:00:00 »
Bitli,

This is exactly what I am doing. My confusion is that the first time I click RTP, I am expecting the options to show up in the RTP preview, but I need to click the RTP circle one more time to see the effect.

Secondly when I apply it globally, I don't see it in the main image.

I will keep experimenting.

For now I used Gaussian Blur in MaximDL - not my preference.

Shailesh

Offline StefanG

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Re: How to remove hot pixels
« Reply #8 on: 2013 December 03 13:08:29 »
Hi Bitli,

I just followed your recipe with an image in linear state and the STF activated. When I open the CosmeticCorrection tool and start the RTP it stays black and stays that way whatever I do with the tool. Do you find the same behaviour in build 1054?
Thanks for your help,

Stefan
GSO RC10
QSI583wsg, SX Lodestar Guider
AP Mach 1 Mount, Eagle Pier
PixInsight, MaximDL, CCD Commander

Offline stevek

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Re: How to remove hot pixels
« Reply #9 on: 2013 December 04 00:15:33 »
Hi, at what stage is hot pixel removal done please?  Just after integration?  On the individual light subs?  After LRGB combination?  I see that it coudl be doen with a cosmetic map with the BPP script?
Thanks, Steve

Offline Andres.Pozo

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Re: How to remove hot pixels
« Reply #10 on: 2013 December 04 00:19:37 »
Hi, at what stage is hot pixel removal done please?  Just after integration?  On the individual light subs?  After LRGB combination?  I see that it coudl be doen with a cosmetic map with the BPP script?
Thanks, Steve
After calibration and before registration of the light subframes. For bayered color images (i.e. DSLR), CC should be applied just before debayering.

Offline stevek

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Re: How to remove hot pixels
« Reply #11 on: 2013 December 04 05:09:11 »
Hi, at what stage is hot pixel removal done please?  Just after integration?  On the individual light subs?  After LRGB combination?  I see that it coudl be doen with a cosmetic map with the BPP script?
Thanks, Steve
After calibration and before registration of the light subframes. For bayered color images (i.e. DSLR), CC should be applied just before debayering.
So how wouldl you do that please?  By running a cosmetic map in the BPP tool?  What if you were doing calibration manually?

Offline Andres.Pozo

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Re: How to remove hot pixels
« Reply #12 on: 2013 December 04 06:07:32 »
So how wouldl you do that please?  By running a cosmetic map in the BPP tool?  What if you were doing calibration manually?
If you use the preprocessing script you have to prepare a CosmeticCorrection icon before launching the script and then select it in the configuration window of the script.

If you are calibrating manually, you only have to execute CosmeticCorrection after the calibration.