The dark frames are taken about once in a month, as three dark exposures of 3600 sec integration each. Since the general dark level of Giraffe is very low, the dark exposures have a mean flux level very close to the bias frames, with the exception of cosmic hits, and the strong glow (see below) in the upper right corner of the detector. This glow is visible on all Giraffe exposures with non-zero integration time. It scales with exposure time. A careful background subtraction should use a scaled master dark.
The dark level is monitored here.
