IMO, the GBRG is the correct demosaicing pattern to use for the 533MC as it looks more natural.
There is much confusion about the correct Bayer/mosaic pattern of the ZWO ASI533MC Pro in this thread.
The single light frame L_2021-04-30_23-26-41_Bin1x1_90s__-10C_2021-04-30_G100.fit (post #16) was captured with APT, and this is its FITS header:
APT-FITS header: BAYERPAT=RGGB, no x and y offsets for the bayer matrix
Let's take a look at the histograms of the debayered single light frame:
1. Using RGGB:
The red and blue channels are different, this is to be expected.
2. Using GBRG:
The red and blue channels are almost identical, this is impossible. (Using GRBG, the histogram would look similar, because only the red and the blue channels are exchanged.)
Assuming that no offsets for the bayer pattern are applied and the origin is 'Upper left corner (top-down)', the above findings prove that the correct Bayer/mosaic pattern is of type XGGY, and not GXYG. And when you try RGGB and BGGR, you will find that only RGGB leads to correct star colors.
The thread from the Sharpcap forum that you cited in post #8 is misleading. This is a FITS header of a different light frame captured with Sharpcap and a ZWO ASI533MC Pro:
Sharpcap-FITS header: BAYERPAT=GBRG, BAYOFFX=0, BAYOFFY=1
Sharpcap uses x and y offsets for the bayer matrix. Unfortunately, it uses unusual keywords (presumably own creations) instead of the widely accepted nonstandard FITS keywords XBAYROFF and YBAYROFF (created by SBIG, now Diffraction Limited, see https://cdn.diffract...Definitions.htm ) that PixInsight evaluates as well. This is the reason that the weird comment has been added by Sharpcap "NOTE: Use RGGB on some software (eg PixInsight)". I wrote a personal message to the creator of Sharpcap hoping that this incompatibility will be fixed soon.
In the Sharpcap forum, section Help and Support/Bug Reports, I just found a thread of April 18, 2021 "Issue with FITS files of OSC camera generated by Sharpcap" in which it was requested to include the FITS keywords XBAYROFF and YBAYROFF. Dr. Robin Glover, the creator of Sharpcap replied that in version 4.0 of his software, these keywords will be written to the FITS header additionally.
Edited by bulrichl, 05 May 2021 - 11:17 AM.