optimize and calibrate for the dark?
if the master dark was not bias-subtracted, then if you want to scale it, you need to bias subtract it at ImageCalibration runtime. that is what "calibrate" means in the dark configuration. also, if you've loaded an uncalibrated (non-bias subtracted) master dark, then you should uncheck the master bias frame if you don't check 'calibrate'. otherwise you'll do a double bias subtraction.
"optimize" means to scale the dark to minimize the noise in the calibrated light. if your dark duration does not match the light duration, then it's probably a good idea to optimize the dark because otherwise you'll subtract too much dark signal from the lights.
rob
