I downloaded a single frame dark frame (fits file) from QHY forums. Fits dark frame had dimensions of 3584 x 2574 pixels = 9225216 pixels = 9.2 MegaPixels.
I don't understand how the dark frame fits file I downloaded has more pixels than the image sensor's total pixels? Can someone shed light on this for me please?
Edit - one thing I can see from the raw dark frame is exactly how many pixels are usable at least. The active area is defined, then I can see the area Terry is talking about (55 columns, no rows), as these pixels are brighter than the rest, but still capturing data. There are pixels near the edge that are either black or just single columns that would not be usable.
From a rough calculation I see approx 3425 x 2569 usable pixels (with the use of a flat frame) = 8.8 MP
I got the dark frame fits file from
this page.