Warning: No correlation between the master dark and target frames (channel 0)

[m_abukhalid]

Hello,

I am very new to pixinsight (been using it for about 3 days now and mostly waiting for processes to finish). I like to way everything is broken down and have been using the following systematic tutorial to do my pre-processing:
http://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html#Section3

The tutorial is very detailed and clear and has enabled me to do a rewarding first pass with only darks for calibration... I saw the warning captured in this post's subject while calibrating my lights (No bias frames were subtracted at all at this stage) and I tried to mitigate it by including the keywords "lower-range 0 upper-range 65535" for the inputs since I was using fits files per the tutorial... it really didnt change much and I plowed through anyway. Since it occurs for every file, I believe that means that I am not doing any Dark correction for my images. Is that true?

So I am currently doing my second time around for the same image, but this time I am trying to calibrate with bias, dark and flat frames. I've switched to exclusively using .xisf files (including converting the original raws for lights, darks, bias and flats to this format) from beginning to end, and yet when calibrating flats and lights, I am still getting the same warning each and every time. Am I doing something wrong or is this just an indicator that I shouldnt worry about hot pixel rejection (I know wishful thinking).

My current workflow per the tutorial is simply:
1) Convert everything to .xisf format
2) Integrate Bias then generate Superbias. 250 Bias frames created at the same ISO and Focal length as the Lights and Darks.
3) Darks Calibration with the superbias (30 Darks taken after each set of lights at the same Focus point, focal length, aperture, shutter speed and ISO as the lights)
4) Calibrated Darks Integration
5) Flats Calibration with Superbias and Master Dark - (30 flats taken later at home) Constantly getting no correlation with master dark
6) Calibtated Flats Integration
7) Light Calibration with Superbias and Master dark and flat - Constantly getting no correlation with master dark

The process continues but up to this point Id like to verify what Im doing wrong to be getting this warning since the next step, I will be using this master dark, which the script is rejecting, to do my cosmetic correction. Can someone please advise if this is an issue and how I can go about correcting it?  Note that the actual lights and darks are all typically 3-8 seconds as all my images are untracked at the moment.

[bulrichl]

Please read my Guide to PI's ImageCalibration:

https://pixinsight.com/forum/index.php?topic=11968.0

Then try the following approach (I maintained your numbering):

1) If you start from FITS files or raw files from a DSLR camera, the initial conversion to the xisf format is not wrong, but it is unnecessary.
2) Integration of bias frames and generation of superbias: OK.
3) Don't pre-calibrate the dark frames.
4) Integrate the uncalibrated dark frames.
5) Calibrate your flat frames with the superbias only.
6) Integration of the calibrated flats: OK.
7) Light frame calibration with the settings in section 4 of my guide (either WITH or WITHOUT dark frame optimization - it's up to you).

Bernd

[m_abukhalid]

Hi. I was just reading it! I modified my workflow and that seems to resolve the error!. Ill use that for now:) Thanks!

[m_abukhalid]

3) Don't pre-calibrate the dark frames.
4) Integrate the uncalibrated dark frames.

Bernd

Hi Bernd,

Doesnt that mean that when I do cosmetic correction I will be using an uncalibrated dark master? Is that ok or do I need to calibrate the master file for this step?

[m_abukhalid]

Can someone confirm whether it matters during cosmetic correction that the dark master used is first calibrated with the master superbias or not?

[bulrichl]

In CosmeticCorrection, the outliers in the MasterDark are identified. The subtraction of a nearly constant value (superbias) is not going to change anything in this respect. So I am absolutely sure that you can use the uncalibrated MasterDark, it will make no difference for CosmeticCorrection.

Bernd

[m_abukhalid]

Thank you very much

[kmachhi]

I get the same warning message, however it while calibrating the light frames this message appeared for 6 of the 31 flat frames the remaining 25 frames did not produce this warning message. My flat dark frame is un-calibrated.  Why would the message appear for only a few frames?  And while integrating the flat dark frames can I use the ones that resulted in this warning or discard them?

Thanks,
Khushrow