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Subtracting Dark frame issue

John Carter
in PixInsight
An exercise in frustration. I just want to tinker with subtracting a dark frame from a light frame using PixelMath.

My equipment: Canon 70D using an 18-55 lens set at 18mm with f/3.5.
Target: Somewhere between Eltanin and Vega.
Seeing: Scattered clouds, intentionally, don't care.
Exposure: 10s @iso1600

I have a single Dark frame and Light frame of 10s each. After using PixelMath to subtract the Dark frame from the Light, many of the hot pixels are NOT removed as shown by blinking between the Dark and Light frames.

The hot pixels are in fact amplified with any amount of MultiLinearTransformation applied to the Light.

So I went a little deeper and created a master Dark and a master Bias (10 frames each) and used the Masters to calibrate the Light (Stars_03-(MasterDark_10s-MasterBias)). No change.

Why won't all the hot pixels get subtracted? What am I doing wrong?

Comments

  • BlockHeadBlockHead
    Hi John,

    It says the files are unavailable or I do not have permission. 
    You might need to change the permissions on them.

    Typically, without looking at your images, what you describe is either a noisy sensor or a poor/mismatched dark frame. Non-cooled sensors of a DSLR are particularly prone to poor calibration because they are noisier and not actively cooled. With active cooling there will be a better match between darks and lights. 

    -theBlockhead
  • John Carter
    I actually resolved this problem by taking a new set of darks.

    I do need to be more aware of how I set permissions on my shared folders. Sorry.
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