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
M81 and M82 mosaic field at F360 (William Optics Zenithstar 61 / EOS550d) PixInSight platesolving and annotation of Galaxies and DSO. Drizzle data integration of many frames at ISO400, 600sec with CLS (Svbony) and UHC (Optolong) 2″ filter.
Telescopi o obiettivi di acquisizione: Williams Optics Zenithstar 61 APO Camere di acquisizione: Canon EOS 550D Full Spectrum ir cut Montature: Skywatcher EQ35M Telescopi o obiettivi di guida: QHYCCD QHY Mini Guide Scope · SVBONY SV106 60mm Guidescope Camere di guida: ZWO ASI120MC-S · QHYCCD QHY5L-II-C Riduttori di focale: William Optics Adjustable Flattener Flat61 Software: Adobe Lightroom · Astroberry · Pleiades Astrophoto PinInsight · KStars Ekos/INDI, Astroberry OS · Photoshop · Stark Labs Phd2 Accessorio: SVBONY Filter Wheel 2″
Drizzle data integration by PixInSight of 102 frames at ISO400, 600sec, UHC 2″ filter by Optolong. Frames taken in many different stage among 08/10/2020 and 25/11/2020 from home balcony. Postprod.: Photoshop and Lightroom