I recently purchased the LED tracing pad that you recommended in one of your equipment emails, to use to capture my flat calibration frames at the same time I do the darks (I had been doing them the next day in the sunshine).
I'm finding that when I have the exposure set so that the histogram is in the middle range, the flat frames have a blue tint (vs. grey) to them. I get the same result if I use a white cloth between the light pad and my telescope or have the light pad directly against the telescope. If I speed up the exposure, so that the histogram is almost all the way to the right, the flat frames are almost completely white.
I'm assuming the blue tint is from the "white" light in the tracing pad, that has some underlying blue in it? Are the flat frames with that blue tint alright to use in the stacking process? Should I do something to adjust the white balance in my camera (Canon Ra) to compensate so they look more grey? Or should I go back to my sunshine routine?