I revisited M101 and gave the RGB imaging a second try with a different light pollution filter, my old Orion Skyglow filter. The results from the IDAS LPS-D1 were better in the end. I ended up combing the RGB data from both filters and cropping the image to stay away from some ugly business around the perimeter of the combined image.

NBRGB Version (final):

NBRBG image generated from OSC RGB data and H-alpha NB data using the Pixinsight NBRGB combination script. Red was augmented by H-alpha data with a scale factor of 5.0.

RGB Version:

Captured OSC RGB images using an LPS-D1 filter on the night of May 24, 2019 and an Orion Skyglow filter on June 3, 2019 . Pre-processed using PixInsight Batch Pre-Processing (BPP) script. Images calibrated using darks, bias, and flats. Using the LPSD1 filter images, Stacked 21 subs (240 sec at ISO 200) for a total integration time of ~1.5 hours. Using the Orion Skyglow filter images, Stacked 36 subs (240 sec at ISO 200) for a total integration time of ~2.5 hours. Post-processed in Pixinsight: Cropped, gradient removal with ABE, MLT for noise reduction, Background Neutralization, Color Calibration, SCNR, stretched using Arcsinh then Histogram Transformation Tool, Curves Transformation, HDR transform, Local histogram transform, and Color Saturation boost.

H-alpha NB Version:

Captured narrow-band H-alpha images using an Optolong 12nm Ha filter on the night of June 22, 2019. Processiing in PixInshight. Calibrated using batch pre-processing (BPP) script using darks, bias, and flats. Extracted red channel. Registered and stacked using StarAlighment and Integration. Total integration time of ~2 hours using 21 subs at ISO400x360 sec. Post-processed in Pixinsight: Cropped, gradient removal with ABE, MLT noise reduction, stretched using Histogram Transformation Tool, Curves Transformation, TGVDenoise, HDR Multiscale Transform, Local Histogram Equalization, and Morphological Transformation.