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M101 Pinwheel Galaxy


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Here is M101, the Pinwheel Galaxy, Messier 101, NGC 5457. Mono RGBs and Ha composite.

I took the exposures in March this year but wasn't able to make much of them until now. Affinity Photo, Topaz DeNoise AI and GradXpert arrived on my computer.  

Stars still aren't right - StarNet2 took quite a lot of the galaxy detail with it on star extraction, so processed with stars in place.  Probably the wrong choice - I might have another go if the rain keeps up!

The exposures were done 3x3 binning, the target so faint, so I think a lot of the stars in the galaxy arms get absorbed into the general low resolution glow or are a bit blocky. I think 2x2 or even 1x1 binning might be possible to resolve more stars with longer exposures in the 15-20 minute range.  It would be a marathon tho'.


Pinwheel Galaxy, brightest member of the M101 Group of galaxies, part of the Virgo Supercluster and our Local Supercluster.

Photograph taken in Astronomik RGB broadband filters, Ha narrow band filter. Total exposure time 12.2 hrs.

R 3x3 bin - 18x300s (West side) = 1.5hrs, 18-19 March 2022
G 3x3 bin - 13x300s (West side) = 1.1 hrs, 24 March 2022
G 3x3 bin - 33x300s (West side) = 2.75 hrs, 26-27 March 2022
B 3x3 bin - 13x300s (West side) = 1.1 hrs, 25 March 2022
B 3x3 bin - 33x300s (West side) = 2.75 hrs, 27-28 March 2022
Ha 3x3 bin - 18x600s (West side) = 3.0 hrs, 25-26 March 2022

Imaging scope: SW Startravel 150mm F5 Refractor, 2.5x Celetron Luminos 2inch imaging barlow, Atik 460EX mono

Guide scope: SW Evostar 90mm F10, with guiding XY stage, ZWO 120MM camera

Guiding: 2 stage PHD: high frequency guide scope (mount tracking) and low frequency OAG image train guiding (guidescope flex)

Mount: Home made German Equatorial pillow block mount, permanently rooftop mounted.  Spring loaded DEC axis gearing.

Other gadgets: ST4 based anti vibration shutter, ST4 based PEC

PixInsight: Lights, Darks, Flats, Biases, Align Calibration, StarNet2 star removal/star layer
GradXpert: Gradient removal
Topaz DeNoise AI: Noise removal
Affinity Photo: 32 bit image processing (curves, high pass masking, selective colour)

M101 Pinwheel galaxy_P2_16_flipH.jpg

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