John - I am quite surprised you are taking on the topic of FPN - since so far you have completely avoided the term.
Unfortunately, the literature is fairly clear on using FPN to refer to spatial noise in the bias and in dark current - but the literature is divided on the use of the term for PRNU - since it is not a noise term intrinsic to the sensor - but involves the photon signal also.
In addition, the odd mosaic stuff in the image you refer to - is probably due to the bayer pattern itself - and has nothing to do with FPN or PRNU in the sensor. It appears to be an artifact of showing a bayer pattern gray scale image at lower resolution.
I did a study of PRNU in ASI600 and was surprised it was so small.
In that study I found the PRNU in an asi1600 to be on the order of 0.56% - which is very small and would never show in the images above.
So - the screendoor stuff in the image above should be ignored and has nothing to do with FPN.
FPN is important and shows in the bias and darks. PRNU shows in the calibrated flats - but is usually a very small noise term - and only applies when there is a strong light signal in the image.
If this is a monochrome camera then a Bayer pattern shouldn't apply as a factor here - but at the same time I think the grid pattern is due to something odd about the way the image has been resampled. But I don't think it is due to PRNU or FPN.
Edited by freestar8n, 15 December 2017 - 05:26 AM.