Hi jmacon,
Thanks for your reply ! I would like to keep it simple: same exposure on both cameras, typically 10min. Do you have experience if both cameras can be connected to the same instance of PHD ? That is crucial, because it makes the second instance & camera wait until guiding is calibrated/settled. This is valid for a meridian flip as well I suppose: I think the second instance will detect that PHD is not guiding, so it will restart the current frame. I will loose some minutes on the second camera, but that’s not a problem.