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Celestial hemisphere:  Northern  ·  Constellation: Ursa Major (UMa)  ·  Contains:  M 101  ·  NGC 5457  ·  NGC 5461  ·  NGC 5471
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M101 in Ursa Major. RGB with HII regions in Ha, weine006
M101 in Ursa Major. RGB with HII regions in Ha
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M101 in Ursa Major. RGB with HII regions in Ha

Getting plate-solving status, please wait...
M101 in Ursa Major. RGB with HII regions in Ha, weine006
M101 in Ursa Major. RGB with HII regions in Ha
Powered byPixInsight

M101 in Ursa Major. RGB with HII regions in Ha

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Description

Two nights on a classic galaxy season target that I first shot four years earlier. First night SQM 20.6 without any moon, second night, 1/3 moon until 2 am, SQM 20.4. 
Since the galaxy is the main object here,  I made a significant crop from the initial full frame 6200 image of ~ 9400 x 6400 to the final ~3300 x 2600 pixels. 
I wanted to highlight the star-forming HII regions so used 3 nm Ha filter on both nights after the RGB subs. 
All in Pixinsight:  WBPP for four masters. Registered RGB to Ha. Cropped. ImageSolver, ChannelCombination for RGB. SPCC with BN using Antlia filters and Sony sensor settings. 
GradientCorrection. BXT at 50% sharpening on both RGB and HA.  SXT to both. Split starless RGB into 3 channels. Used ContinuumSubtraction script then NXT at 90% denoise and 0% detail. 
Used CombineHaWithRGB script with Ha Amount 1.5, beta 0.15 (adds Ha also to blue channel) Background noise 0.15. 
Extracted L from this HaRGB Starless image, stretch and clipped to mask background and used Curves to increase saturation slightly on galaxy. Then GHS stretch x 3 with final black point adjustment in linear. Masked background then LHE about 25% amount at two kernel sizes. On RGBStars: ArcSinH stretch.
Used ScreenStars script to add back RGB stars but then tiny stars around nebula were overexposed and also got what I call “White dot artefact” in the HII regions.  So, on the RGB stars, I masked background and did a negative HT "unstretch" to dim stars that would be on top of galaxy. That looked better after combination. I wanted to enhance yellow in the central core only so used Range mask generator on RGBStarless, isolated the core only and clone stamped out residuals outside galaxy. Fuzzed with convolution. Then Curves R and G channels to make yellow with slight saturation boost.  With mask still on, SCNR at 100%. Cropped a bit more.

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  • Final
    M101 in Ursa Major. RGB with HII regions in Ha, weine006
    Original
  • M101 in Ursa Major. RGB with HII regions in Ha, weine006
    B

B

Title: Increase blue saturation in the galaxy arms

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M101 in Ursa Major. RGB with HII regions in Ha, weine006
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