Stuck shutter?

[Coco]

lol... really should read all the thread

[steppenwolf]

Shades of Déjà vu here! The column from the star is something I have seen with my OSC CCD camera and ties in with the issue that I had with my flats but it took a short while for me to make the correct connection. When I am focusing my OSC camera, I use short (6 second) 2 x 2 binned exposures on a bright star and frequently get a vertical column rising from the chosen star. This line is normally dotted which is why I didn't immediately see the correlation with my flats issue but they are both related to short exposures.

The 'OK' flat (post #18) may in fact not be OK as it is so burnt out that it is not easy to see if there are vertical lines or not - but that may be a red herring.

Your 'faulty' QSI flat is very similar to my faulty OSC flat but that may just be a coincidence but increasing the exposure time would be well worth testing for.