Bob - I have the same camera and didn't realize until this thread that there was a choice. Reading the documentation from QSI I would think Electronic would be the choice as this would not require the shutter to move on light exposures. The mechanical shutter would only be used during dark and bias subs.
"
Shutter Priority - Settings are “Mechanical” or “Electronic”. This setting can only be changed
on cameras with interline transfer CCDs . In “Mechanical” priority the shutter is closed after each
exposure. In “Electronic” priority the mechanical shutter is left open unless the camera is
exposing a dark or bias frame. Electronic priority provides the highest possible frame rate when
taking short exposures."
I've had a few issues with flats and the shutter, I'll bet it is set for mechanical priority.?
Pete
