M81 and M82: Ha and Oiii integration to RGB

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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.

For Rista excellent studies, please cfr. https://jonrista.com/the-astrophotographers-guide/the-zwo-asi1600-guide/the-zwo-asi1600/preliminary-analysis/ and https://www.cloudynights.com/topic/578198-short-exposure-time-asi-1600mm-cool/ both on 02/08/2023.

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 M82 filed mosaic and annotation

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Astrobin: https://www.astrobin.com/y6ao2p/

Astrometry: http://nova.astrometry.net/user_images/4612086#annotated

Annotated mosaic frame (by PixInSight)

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.

M81 / NGC3031, M82 / NGC3034, NGC3037, NGC2976

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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″

Astrobin: https://www.astrobin.com/x1yn81/

Astrometry: https://nova.astrometry.net/user_images/4357793#annotated

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

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