PixInsight - Master Calibration Files

Master Dark and Master Bias Calibration Frames

updated: updated: 2021-08-20


The  Image Integration module is used to generate the master bias and dark frames 
The same settings will be used in this module for generation of master bias and dark frames. So we'll run the integration twice: first for the bias frames and then again for the dark frames (bias subtraction of dark frames will take place with the IC tool).

There are several important settings to pay attention to:

  • Don't normalize the images, because the bias pedestal must be preserved. Both normalization methods in the Image Integration and Pixel Rejection (1) sections must be disabled (No normalization setting).
  • To be meticulous, the image weighting feature must also be disabled. We want to perform a strict average of a large number of frames, rejecting only clear outliers.
  • To reject possible outliers, I recommend the Winsorized Sigma Clipping algorithm, in case we have a large number of bias and dark frames. A permissive clipping point of 3×sigma can be useful.


Process 🡺 All Processes 🡺 Image Integration


Dark and Bias calibration frames


Master Dark and Bias frames

Previous Step

Image Integration

Next Step

Image Calibration


PixInsight — Master Calibration Frames: Acquisition and Processing



Master Dark Frames

Master Bias Frames


Open the Image Integration module


Add Dark or Bias frames


Image integration settings to be used


  • don't normalize the images
  • image weighting must be disabled (all weights = 1)
  • Scale estimation: 
    • Biweight midvariance
    • or MAD (Median absolute deviation)


Pixel Rejection (1) settings

  • don't normalize the images
  • for 5 to 30 frames: use Winsorized Sigma Clipping 
  • if more: use Sigma Clipping


Pixel Rejection (2)


Run the Integration

Click on the (Apply Global) or hit F6

The master dark frame on the right is a typical result of an ASI294, you can clearly see effect from the heat generated by the electronic components behind the  sensor chip (image is stretched).


Save the master calibration files

use meaningful file names, see example




Next Step: Master Flat Generation (I)

Read this article for more information: PixInsight — Master Calibration Frames: Acquisition and Processing

and: Astrophotography by Rob Kantelberg (astro-imaging.com)

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