During 2021 and 2022 I took a good number of subframes focusing on M81 and M82 field and I planned to integrate RGB channels with Ha and Oiii narrowband contribute.
Being a follower of John Rista short time DSO photography approach, RGB channel subframes I recorded at 60″, Halpha and Oiii subframes at 180″, William Optics Redcat51 and ASI1600mm Pro at -20 Celsius, Gain 139.
After standard calibration, cosmetic correction by dark-master, star registration and winsorized sigma clipping integration, I obtained masterframe for each channel recorded.
Channel combination of RGB generated a good integration which I played with Ha and Oiii masters to Dynamic BG removal, solving (and annotated transparent layer version for further work), Spectrophotometric Color Calibration (just RGB) deconvolution and denoising.
I then proceed by starXterminator in starless and stars version of each master to work properly ‘till putting them back by PixelMath, obtaining a pretty good RGB master
with ready-to-go Halpha and Oiii narrowband master to integrate within:
H alpha channel to be associated to R channel while Oiii to differently be integrated with both G and B channels.
Narrowband with RGB integration produced a pretty good result which, in turns, I little worked over separating again stars and starless sub-master, finally directly melted in Photoshop.
This portion of sky is so rich of galaxies; PGC annotation (PixInSight) gives an idea of the richness of field
I thus start to try some crop solution for better framing and focusing the final image. At first I cropped a squared and a vertical version to catch in the field also NGC2976, NGC2961 and NGC2959.
Finally I focused about M81 and M82 with a deep cropping for an orizontal composition, trying to dispose M81 and friends according to 3/4 grids basic composition rule.
Photoshop, non cropped version, with 3 main crops framing as guide layer are available here
Reprocessing 2022 records focused about M42 region. In this work there’s a main core in LRGB, background removed, SPColorCalibrated, Deconvoltued and denoised is then integrated and boosted by Ha and Oiii narrowband master (Bgremoved, Deconvoluted and denoised) with Ha applied to L and R channel, Oiii to Green and Blue. Final starless and 0.65 stars pixelmath blended and Photoshop retouches.
In this workflow I used Ha narrowband as integration for Luminance and Red channel, and Oiii narrowband master as integration for Green and Blue channel as according to Kayron Mercieca, cfr.: https://www.lightvortexastronomy.com/tutorial-combining-lrgb-with-narrowband.html Approved subframes detailed list (PixInSight weighted) resumed gathered by filter, all by Astronomic, recorded between 28/10/2021 and 25/04/2023. Ha: 226 x 180″ -20C: 141 gain 139, 85 gain 173 Oiii: 159 x 180″ -20C: 94 gain 139, 65 gain 173 L: 636 x 60″ -20C: 553 gain 139, 83 gain 173 G: 532 x 60″ -20C: 373 gain 139, 159 gain 173 B: 500 x 60″ -20C: 298 gain 139, 202 gain 173 R: 614 x 60″ -20C: 438 gain 139, 176 gain 173
IC 2574 in HaR OiiiG OiiiB, William Optics Redcat 51, ASI1600mm Pro at Bin1, -20C: RGB subframes of 60″, Ha and Oiii subframes of 180″
Ha is used as integration of R channel, Oiii as integration of G and B channel by PixelMath, PixInSight.
IC 2574 (Coddington’s Nebula) – Intermediate Spiral(SABm) Galaxy in Ursa Major, an intermediate Spiral(SABm) Galaxy in the Ursa Major constellation, situated at about 17.000 Ly from us, appears close to the northern celestial pole and, as such, it is visible for most part of the year from the northern hemisphere.
It is an outlying member of the M81 Group and is currently forming stars; a UV analysis showed clumps of star formation 85 to 500 light-years (26 to 150 pc) in size.