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Amp Glow

Malcolm Park
in PixInsight
Hello,
I seem to get good results removing amp glow in calibration, with the exception of my Ha data. 
I am using L R G B and Ha data. 
The Ha shows black flecks where the bright amp glow once was. 
The other data do not. 
I tried processing the Ha data on its own by setting a pedestal value of 500 in WBPP but that just seemed to make it worse. 
Any suggestions? 

thanks,
Malcolm 

Comments

  • BlockHeadBlockHead
    Hi Malcom,

    Those "black flecks" are a red flag for a symptom I cover. 
    Did you see this video in the WBPP series (and others)?:


    I am suggesting you likely need to have a pedestal. The reason you do not see an issue in your broadband images is that the sky is so much brighter... it IS a natural pedestal.. something you do not have in Ha (and other NB).

    -the Blockhead
  • Malcolm Park
    thats why I tried adding the pedestal value, because I watched your video. But in this case it made it worse.

    thanks
  • Malcolm Park
    edited December 2023
    maybe 500 was too much? I guessed that the higher the pedestal value I selected, the less dark the artifact would be 
  • Malcolm Park
    lets see if this uploads
    pedestal.jpg
    4550 x 910 - 2M
  • Malcolm Park
    just for reference this is the ampglow pattern of the ASI183mm pro
    ampglow.JPG
    1125 x 767 - 149K
  • BlockHeadBlockHead
    Is your Gain and pedestal setting on your camera (this is different than the WBPP setting) the same for the darks and lights? Did you use the same software to acquire the darks and lights? Are you darks for the flats the same exposure time? You are not optimizing correct?

    -theBlockhead
  • Malcolm Park
    hm.
    good questions! 
    Lemme look 

    thanks!
  • Malcolm Park
    Dark, Flat Dark, Flat and Light all have the same Gain/offset per FITS Headers.
    All acquired in SGP.
    Dark flats are same exposure, same temperature.
  • BlockHeadBlockHead
    One more...

  • Malcolm Park
    Gain 210, Offset 10

  • Malcolm Park
    maybe I don't have enough signal? I only have 8 x 600s in Ha
  • BlockHeadBlockHead
    edited December 2023
    Offset 10? Hmmm... 
    I was referring to the optimization question. 
    Also... the darks and lights are the same age (e.g. the darks are not months old)?

  • Malcolm Park
    I assumed that since you mentioned them together, perhaps pedestal was another word for offset. There's no setting for pedestal in the ascom driver settings. I don't know where else to look for a setting on my camera.
    All the files were created within a week or two of each other. 
  • BlockHeadBlockHead
    Gain and Offset are electrical adjustments for your camera.
    Pedestals (in PixInsight) are mathematical constants added to values when doing image calibration. 
    They are different. 

    You can make 15 of each raw file available if you want me to look. 
    Not much remains if you are not optimizing (which I assume and hope you are not). 

    If your AMP glow in your dark frame is different in intensity than your light frame (given everything you have said so far)- your camera is simply faulty. These sensors are linear unless something is wrong.

    -the Blockhead
  • BlockHeadBlockHead
    Indeed... just to followup. Your Ha frame is effectively a dark frame. Ignore the stars and nebula in there... the background sky is so dark ...there is effectively no light there. 

    You should be able to take two dark frames and subtract them from each other and NOT have many zeros (black). Do you see my logic?

    -the Blockhead
  • Malcolm Park
    I do see it. 
    I have to admit, earlier I didn't even know what you meant by optimizing. 
    Were you asking me if I checked optimize master dark in WBPP?
    I did not. 
    I have used that only when my dark and light exposure times do not match. 
    I have understood that a dark can be corrected with a bias to adjust for the difference in exposure time. 
    I rarely have do this.  

    regards to this question: "Is your Gain and pedestal setting on your camera (this is different than the WBPP setting) the same for the darks and lights?"  
    Is there a pedestal setting on cameras? where? This is what I thought you meant by offset. 
  • Malcolm Park
    edited December 2023
    just for the record, I got the same result in Astro Pixel Processor. The amp glow was "over compensated" leaving black pixels. 

    I think a good test would be to re-do all the calibration files and ensure that everything is done right. 
    It seems unlikely the solution lies in Pix if APP gets the same result. 

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