Having recently increased my exposure times up to 30 minute subs I am now in need of taking the same length exposures for my Dark frames. I understand the need to take multiple dark frames as part of the calibration process, usually more is better (up to a point). In fact I use a Master Dark when calibrating in PixInsight.  That is once I have taken my darks frames I go through the Image Integration steps in creating the master dark file so that I only have to reference this one file from t