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Black/color pixels at the center of the stars (Drizzle, Integration, CFA)

Euripides
in PixInsight
Hello,

I am trying to find out for hours the cause for this issue and I think I've found it, but I am also a little bit confused.

First of all the issue: Black/color pixels at the center of some stars, look at the Drizzle.png. In addition to that my straight of of camera lights are free of that issue.

You think that this would be an issue with the drizzle. So I went back to the integration (Integrartion.png). Issue was there too.

Then I thought this would be an integration issue with the Pixel Rejection algorithm and the rejections (example, clip high pixels etc). Nop, tried everything and the issues was still there.

So I went back to a single frame "Calibrated, Cosmetic Corrected, Debayered" (LCCCD.png). Guess what, still there.

Ok, I said I've found it, that has to be the Cosmetic Correction. (Followed Adam's footsteps with the WBPP and the Auto hot 3px).

But....no... Even without the Cosmetic Correction, the issue was still there! (LCD.png)


So let's go the the WBPP:


I've found that the cause of this issues is the CFA = ON at the Cosmetic Correction panel. (CFAon.png)
When the CFA = OFF, issue is gone! (CFAoff.png)


And here is where I am confused...
The tooltip says about the CFA checkbox:

"Enable this option if the image has been mosaiced with a Color Filter Array (CFA) or Bayer matrix (OSC, CCD, DSLR camera)."
This is true in my case scenario cause I have a Color Camera, so I turned this ON.

"Disable if the image comes from a monochrome imager or has already been deBayered".
No I don't have a mono camera, and the image has not yet been deBayered, cause the deBayer is the final stage of the WBPP, is that correct?

Calibrate --> Cosmetic Correction --> Debayer , correct?









Comments

  • Euripides
    In addition to that, I've already re run from scratch with a CC and CFA off. Nothing changed.

    Now I took a single light frame and just make a preview with Cosmetic Correction. With the CFA = OFF the auto function shows about 700 pixels and with CFA = ON about 4000.

    So I really do not know if I have to bother with CC on those images.
    MapCFAon.png
    2878 x 1774 - 416K
    MapCFAoff.png
    2870 x 1772 - 378K
  • BlockHeadBlockHead
    Ok...first with respect to Drizzle... this is a WBPP issue that I pushed to finally have an answer to. 
    Did you see Juan answer this finally! (I posted this on the FB forum as well). 
    (you will need to scroll down on the first page to see Juan answer as to what happens and how it will be fixed in the future)

    And yes, you are correct about the CFA. You check it when you are giving WBPP grayscale images that have a CFA. If you give WBPP a grayscale image OR you give it already debayered images you do not check. The reason for the second part is that WBPP can be used to weight/align/combine already debayered images. (you would not calibrated debayered images). So..I am not certain if you are really confused..you seem to understand!

    -the Blockhead
  • Euripides
    No I haven't seen it before, thanks!


    But if I get it straight, Juan says that the issue appears when the WBPP produces the intergraded image, correct?


  • Euripides
    Beside that, I think that finally my issue is different, or at least is the cause of the problem if we combine it with the WBPP.




    Here is a straight of camera light frame. After the debayer, I tried the CC with Auto Hot Pixel 3.0.

    If I have the CFA on I can see those pixels. In fact I have to raise the Hot Pixel over 15 to eliminate them.
    If I have the CFA off there is no issue.


    CC_CFAon.png
    2923 x 1761 - 1M
    CC_CFAon.png
    2923 x 1761 - 1M
  • BlockHeadBlockHead
    Hi,

    I am afraid I am lost.
    The image you attach above is a grayscale image that has not been debayered. 

    Can you make your data (or a fraction of it) available?

    -the Blockhead

  • Euripides
    Thats correct!

    I've made available the straight out of camera image, for everyone who wants to take a closer look, without any edit from my side.

    Then I took this image and used the Debayer process (RGGB). 
    On that output image I've run the Cosmetic Correction as per the images attached.

    Sure I can upload my data but I don't think will help more, cause I can see the "issue" from the start, just running the CC on a debayered image, without touching anything else. 
  • BlockHeadBlockHead
    You have turned off your camera's automatic dark frame subtraction correct?
    -the Blockhead
  • Euripides
    Hmm if I recall correctly this is a feature on a DSLR right? If there is something similar on the 533C I'm not aware of :-(
  • BlockHeadBlockHead
    Sorry..I thought you had a DSLR.
    So... you say the issue is in the raw untouched data... that would be strange...but if the data is signed it could be possible. can you make some raw data available that show the issue?
    -the Blockhead
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