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Basic Image Calibration

stevereilly
in PixInsight
Due to BPP not dealing with rotator E/W flats I've always used the manual Image Calibration routine to calibrate my images then follow with Cosmetic Correction and then Star Align. I always have a current master flat library as well as master darks and master bias. It's been my process to only use the master bias when calibrating the flat frames and am beginning to question that. My images, all including darks and bias frames, are taken at the same temperature and time duration.

My light frames are typically 15 minute for broad band and 30 minute on narrow band. My darks are 15 and 30 as well so there's no scaling the darks. In the calibration of the light frames do you use both your master bias and master dark frames or just the master dark? What frames for creating the master darks?

Comments

  • BlockHeadBlockHead
    Steve,

    If you have matching darks for light frames, you simply use those dark frames. No bias is involved. 

    There are only two reasons to use a bias. 
    1. Scaling Master Dark Frames (you are not doing this).
    2. Calibrating Flat Field images 

    So the biases can be used for the calibration of flats. If you generate matching darks for your flats- then no biases are necessary at all. If you think biases are an issue- just make matching darks and compare. 

    WBPP does deal with E/W flats. Your first statement is not accurate. If you get a chance- I hope you review my WBPP tutorials. I specifically point out the example of E/W flats. By the way, I received many e-mails asking me what the #$%! would I ever have flats for different sides of the meridian. In the future...I will send these e-mails to you to answer. :)

    -the Blockhead
  • stevereilly
    Thanks for the reply. That's what I had thought but this last batch of images seemed to have a good deal of column defects and using the master bias resolved all but a few and the images looked more uniform.

    On the BPP, my experience was was the 1st versions of BPP and at that time I could only do east side or west side at a time. Later versions I never looked at as I was set in doing it manually for so long. At least that was my understanding back then.
  • BlockHeadBlockHead
    I would highly recommend you get onboard with WBPP now. 
    I demonstrate in my videos there is *no* difference in results between manual and WBPP...and WBPP offers some the very features you are looking for. 

    -the Blockhead
  • stevereilly
    Among the many projects I have been involved in lately I just have downloaded PI 1.8.8.8 and will look harder at WBPP and your instructions. I always appreciate easier ways to do quality processing hence my subscription. Learning new and proper processes is also always a boost especially when you know you have quality data and want to get the best results from it. I will look specifically for the example of E/W flats and then watch the entire processing series.
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