1. ImagesPlus
  2. Topics

IP not removing hot pixels

Ade51
 

Hi Everyone
I have had a QHY268C for a couple of years now and have always used IP for processing. Recently I have noticed that IP is not removing hot pixels even with the option selected in the automatic processing and if I separately try to remove them.

I suspect that this is because they are not discrete single pixels, but several together e.g. three green in a row or a 3x3 grid of blue with the centre pixel brightest - even in a single frame. I have looked at the darks and I do not see this clumping of pixels.

I have briefly tried Astro Pixel Processor and Deep sky Stacker and they do not produce the same effect, although the image results are not as pleasing as IP. Does anyone know what might be causing this? Any help would be gratefully received.

I will add an image, which is a cropped section to show the effect.

Tony

Ade51
 

Here is a sample image showing the problem pixels

Ade51
 

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Geof Lewis
 

Hi Tony,
If the Auto Image Set Processing doesn't catch all of them, you could try the Reduce High, Low, Bloom Pixels tool found under the Smooth Sharpen drop down list as per below screenshot. Experiment with the slider, but probably push it well towards the right (1.0 end) Also experiment with the window and effect size.



I recall that Blair covered using this tool in one of his RASC sessions, which are available on YouTube, but I can't quickly locate it, so Blair is probably the right person to help with that.
Good luck.

Geof

From: ImagesPlus@groups.io <ImagesPlus@groups.io> on behalf of Ade51 via groups.io <tedwards@...>
Sent: 02 February 2023 14:04
To: ImagesPlus@groups.io <ImagesPlus@groups.io>
Subject: Re: [ImagesPlus] IP not removing hot pixels
 
Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Geof Lewis
 

Hi Tony,
I found Blair's tutorial on YT. It's the one where he deals with Noise Reduction here...
 https://www.youtube.com/watch?v=Lbqj2boQTIc&list=PLebMPxNPb_h1R9-Zci-sXjmV9cTpFcFlb&index=7&t=1575s
If you check out from the 24min point for about 2-3 minutes he covers hot pixel reduction using the Reduce High, Low, Bloom Pixels tool.
Hope this helps.

Geof

From: ImagesPlus@groups.io <ImagesPlus@groups.io> on behalf of Geof Lewis <geoflewis@...>
Sent: 02 February 2023 14:42
To: ImagesPlus@groups.io <ImagesPlus@groups.io>
Subject: Re: [ImagesPlus] IP not removing hot pixels
 
Hi Tony,
If the Auto Image Set Processing doesn't catch all of them, you could try the Reduce High, Low, Bloom Pixels tool found under the Smooth Sharpen drop down list as per below screenshot. Experiment with the slider, but probably push it well towards the right (1.0 end) Also experiment with the window and effect size.



I recall that Blair covered using this tool in one of his RASC sessions, which are available on YouTube, but I can't quickly locate it, so Blair is probably the right person to help with that.
Good luck.

Geof
From: ImagesPlus@groups.io <ImagesPlus@groups.io> on behalf of Ade51 via groups.io <tedwards@...>
Sent: 02 February 2023 14:04
To: ImagesPlus@groups.io <ImagesPlus@groups.io>
Subject: Re: [ImagesPlus] IP not removing hot pixels
 
Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Blair MacDonald
 

Tony:

What are you using as the combine method, average or min max excluded average?



Blair (www.nightanddayastrophotography.com)


-------- Original message --------
From: "Ade51 via groups.io" <tedwards@...>
Date: 2023-02-02 10:04 a.m. (GMT-04:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Ade51
 

Hello Blair

 

I use average. Is that a bad idea?

 

Regards

 

Tony

 

From: ImagesPlus@groups.io <ImagesPlus@groups.io> On Behalf Of Blair MacDonald
Sent: 2 February, 2023 5:55 PM
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Tony:

 

What are you using as the combine method, average or min max excluded average?

 

 

 

 

 

-------- Original message --------

From: "Ade51 via groups.io" <tedwards@...>

Date: 2023-02-02 10:04 a.m. (GMT-04:00)

Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Blair MacDonald
 

Yep. In order to have the dither help to get rid of hot and cold pixels you need to use some form of exclusion combine. I generally use min max excluded average as it produces the best final SNR while removing hot pixels. Simple averaging will not remove the hot pixels.



Blair (www.nightanddayastrophotography.com)


-------- Original message --------
From: "Ade51 via groups.io" <tedwards@...>
Date: 2023-02-02 1:57 p.m. (GMT-04:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Hello Blair

 

I use average. Is that a bad idea?

 

Regards

 

Tony

 

From: ImagesPlus@groups.io <ImagesPlus@groups.io> On Behalf Of Blair MacDonald
Sent: 2 February, 2023 5:55 PM
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Tony:

 

What are you using as the combine method, average or min max excluded average?

 

 

 

 

 

-------- Original message --------

From: "Ade51 via groups.io" <tedwards@...>

Date: 2023-02-02 10:04 a.m. (GMT-04:00)

Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Ade51
 

Blair

Thank you, problem solved.

I had obviously become greedy in terms of total imaging time. I watched the YouTube video on noise and that was very helpful too.

Thanks Geoff as well.

Regards

Tony



Sent from Samsung tablet.

-------- Original message --------
From: Blair MacDonald <b.macdonald@...>
Date: 02/02/2023 19:28 (GMT+00:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Yep. In order to have the dither help to get rid of hot and cold pixels you need to use some form of exclusion combine. I generally use min max excluded average as it produces the best final SNR while removing hot pixels. Simple averaging will not remove the hot pixels.



Blair (www.nightanddayastrophotography.com)


-------- Original message --------
From: "Ade51 via groups.io" <tedwards@...>
Date: 2023-02-02 1:57 p.m. (GMT-04:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Hello Blair

 

I use average. Is that a bad idea?

 

Regards

 

Tony

 

From: ImagesPlus@groups.io <ImagesPlus@groups.io> On Behalf Of Blair MacDonald
Sent: 2 February, 2023 5:55 PM
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Tony:

 

What are you using as the combine method, average or min max excluded average?

 

 

 

 

 

-------- Original message --------

From: "Ade51 via groups.io" <tedwards@...>

Date: 2023-02-02 10:04 a.m. (GMT-04:00)

Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

Blair MacDonald
 

Glad it helped.



Blair (www.nightanddayastrophotography.com)


-------- Original message --------
From: "Ade51 via groups.io" <tedwards@...>
Date: 2023-02-02 5:27 p.m. (GMT-04:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Blair

Thank you, problem solved.

I had obviously become greedy in terms of total imaging time. I watched the YouTube video on noise and that was very helpful too.

Thanks Geoff as well.

Regards

Tony



Sent from Samsung tablet.

-------- Original message --------
From: Blair MacDonald <b.macdonald@...>
Date: 02/02/2023 19:28 (GMT+00:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Yep. In order to have the dither help to get rid of hot and cold pixels you need to use some form of exclusion combine. I generally use min max excluded average as it produces the best final SNR while removing hot pixels. Simple averaging will not remove the hot pixels.



Blair (www.nightanddayastrophotography.com)


-------- Original message --------
From: "Ade51 via groups.io" <tedwards@...>
Date: 2023-02-02 1:57 p.m. (GMT-04:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Hello Blair

 

I use average. Is that a bad idea?

 

Regards

 

Tony

 

From: ImagesPlus@groups.io <ImagesPlus@groups.io> On Behalf Of Blair MacDonald
Sent: 2 February, 2023 5:55 PM
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Tony:

 

What are you using as the combine method, average or min max excluded average?

 

 

 

 

 

-------- Original message --------

From: "Ade51 via groups.io" <tedwards@...>

Date: 2023-02-02 10:04 a.m. (GMT-04:00)

Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony

phils67
 

Removing the high and low pixel value effectively discards two images from the stack. The discards are actually spread out over all of the images on a pixel by pixel basis. Once I know how many images I want in the stack, I just add two to the count and I'll end up with the number I want. Of course, while capturing the images, I also have to account for images that will be dropped because their quality is too low to be included in the stack.

On Thu, 2023-02-02 at 21:27 +0000, Ade51 via groups.io wrote:
Blair

Thank you, problem solved.

I had obviously become greedy in terms of total imaging time. I watched the YouTube video on noise and that was very helpful too.

Thanks Geoff as well.

Regards

Tony



Sent from Samsung tablet.

-------- Original message --------
From: Blair MacDonald <b.macdonald@...>
Date: 02/02/2023 19:28 (GMT+00:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Yep. In order to have the dither help to get rid of hot and cold pixels you need to use some form of exclusion combine. I generally use min max excluded average as it produces the best final SNR while removing hot pixels. Simple averaging will not remove the hot pixels.



Blair (www.nightanddayastrophotography.com)


-------- Original message --------
From: "Ade51 via groups.io" <tedwards@...>
Date: 2023-02-02 1:57 p.m. (GMT-04:00)
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

Hello Blair

 

I use average. Is that a bad idea?

 

Regards

 

Tony

 

From: ImagesPlus@groups.io <ImagesPlus@groups.io> On Behalf Of Blair MacDonald
Sent: 2 February, 2023 5:55 PM
To: ImagesPlus@groups.io
Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Tony:

 

What are you using as the combine method, average or min max excluded average?

 

 

 

 

 

-------- Original message --------

From: "Ade51 via groups.io" <tedwards@...>

Date: 2023-02-02 10:04 a.m. (GMT-04:00)

Subject: Re: [ImagesPlus] IP not removing hot pixels

 

Sorry everyone, I sent the wrong image as I had resampled that one. I have sent another that shows the issue better. The real problem is that when I stack frames dithering leads to very noticeable clusters of these bright pixels that are not easy to remove. So far I do it manually.

Tony


1 - 11 of 11