Is it usual to have a checkerboard pattern in raw flats? (See attached image.) Master flats, which have been reduced, show no pattern. All filters show the same pattern. Thanks!
That is an illusion or visual artifiact caused by the zoom algorithm in whatever software you are using (eg MaxIm DL) - it is trying to fit 61 million pixels into a space that looks to be about 937,000 pixels in size. If you zoom to 100% you will see it isn't present.
