MasterLightLUM STR

Part of the Heart Nebula mosaic with LUM filter Master Light Frame - 60 X 120s exposures

I used 60 DARKs, 60 flats by filter, 60 Dark Flats for calibration. Calibration, Star Alignment and stacking with PixInsight

ORION EON 115mm with ASI1600MM-C with ZWO 7nm Ha, OIII, SII, Lum filters - image capture with Sequence Generator Pro
ORION HDX-110 EQ-G with ORION 70mm/ASI290MM for guiding with PHD2.

There is a clear top to bottom gradient pattern as seen in the LUM Master Flat did not calibrate out from the light frame. Again, I almost think I should just skip flat calibration and see how it looks - the calibration seems to be making the stacked images worse.