I have been using MDL for 8 years and using Flats for the past 5 years with good results. But I am wondering about taking dusk flats west of the merdian and taking Lights both East and West of the Meridian. I have been letting MDl apply my dusk flats to lights from both sides of the meridian during Stacking. Results have been good. All my night sessions are orchestrated by CCD Commander, along with MDl, FocusMax, TheSkyX. MDl does camera control, observatory control and AutoGuiding. CCDC also does my Flats, usually sunset flats When a Meridian Flip occurs, camera orientation in relation to the sky is reversed (I think). If I want to compare an image taken in the east with one taken in the west, to match them up, I must use Flip and Mirror commands. I am wondering, should I only apply flats taken in the west to only lights taken in the west with seperate flats taken in the east with lights taken in the east? I am quessing that I can apply flats taken in the west to lights taken on both sides of the merdian. But trying to figure out what is correct is a bit to much for my old thinker. What is the accepted and best practice? Thank you fellow night sky gazers.