Author Topic: Preprocessing confusion  (Read 431 times)

Offline m_abukhalid

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Preprocessing confusion
« on: 2018 March 03 15:32:02 »
As I understand it, the best way to perform calibration is:
 - Generate Master and Superbias
 - Create Master Dark (non calibrated)
 - Calibrate flat with Bias frame only
 - Integrate master flat
 - Calibrate lights with master Bias, Dark and flat, while setting master Flat and dark to calibrate/optimize on the fly
 - Integrate master light.

Trying to generate pre-calibrated masters in the past  to calibrate the lights has not worked for me so far and besides the error "Re: Warning: No correlation between the master dark and target frames (channel 0)" the output is usually worse than the non calibrated images.

the question I have is regarding flats that are taken at a different ISO. I usually take my flats at ISO200 while my images and darks are at ISO800 or ISO1600. What would be a good workflow to allow me to properly calibrate all my images? I have been advised against calibrating flats with darks prior to light calibration, so I feel stuck...

Offline John_Gill

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Re: Preprocessing confusion
« Reply #1 on: 2018 March 04 00:49:44 »
Hi,

I cannot help much, but Bias, Flats and Darks should all be at the same ISO.  For a DSLR, I shoot Bias at a fast exposure of 1/4000,  for Flats I set the camera to AV and the exposure comes out at about 2 seconds, and for Darks the settings are the same as the Lights (temp is important).

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Offline m_abukhalid

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Re: Preprocessing confusion
« Reply #2 on: 2018 March 05 05:11:45 »
Thanks for the response John. Using the same ISO would resolve my issue but its not always feasible to take good flats at higher ISO. I find that ignoring ISO for flats simplifies the process immensely and still does a great job at eliminating vignetting.