Is this normal or am I doing something wrong?
I took some lights and darks last night with the (unmodded) 350D on the ED80/EQ6. It was reasonably mild, about 18deg-19deg ambient.
The lights look fine (although washed out from light pollution and low altitude), but the darks are incredibly spotty - so when they are subtracted from the lights, I end up with dark spots everywhere.
They're best seen in the full-size versions, so I uploaded a sample image to show you. They're just converted to 8-bit and saved as medium-quality jpegs (around 500kb each).
1.
Raw light image (300s, ISO800)
2.
Raw dark image (300s, ISO800)
3.
Stack of 5 x median combined darks (all at 300s, ISO800) using ImagesPlus
4.
Calibrated light from the stacked dark. You can see the black spots.
Ignore the jpeg compression artifacts.
I've attached a 800px resized version of #4, but as I said it's much more obvious in the full size version.
So, what am I doing wrong?