Spiral Galaxy Messier 106 in Canes Venatici

M 106 is located 22 to 25 million light years away and is a Type 2 Seyfert galaxy with an active supermassive black hole. M 106 is the largest member of the Canes II group, a cluster of about 20 galaxies. This image is mostly LRGB. H-alpha data was blended into the red channel, but not luminance. The only effect was to add a pink hue to strong HII regions of the inner spiral arms. I was unable to get the Ha jet to show effectively, even when I blended it into the luminance channel. The Ha-only image is here.


Exposure: Total exposure time about 17.8 hours LRGB and 6.3 hours Ha. 326 x 2 mins Lum, 64:34:45 x 2 mins RGB, 19 x 20 mins Ha. All bin 1x1. Captured January to April 2018.
Light pollution: Bortle 7-8 (white zone, NELM about 4.5)
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 1.2 arcsecs/pixel (50% reduction)

Equipment:
Scope: C11 (standard, not Edge) with Celestron 0.63 reducer imaging at f5.7
Mount: Paramount MX+, connected via ASCOM Telescope Driver 6.1 for TheSkyX, with MKS 5000 driver 6.0.0.0
Camera: SXVR-H694, connected via SX ASCOM driver 6.2.1.17140 (SX 1.2.2 also installed)
Filter wheel: Atik EFW2 with 7x1.25 carousel and Artemis 2.4.3.0 driver
Filters: Astrodon Type IIi LRGB
Rotator: Optec Pyxis 2", connected via Andy Galasso's 0.4 driver (Optec Pyxis Rotator AG)
Focuser: Rigel Systems GCUSB_nStep with driver version 6.0.7
OAG: Orion Thin OAG
Guide cam: Lodestar (first generation). 4 second exposures
Automation SW: Sequence Generator Pro 3.0.0.4 beta
Guide SW: PHD2.6.3, connected to guide cam via native SXV driver
ASCOM: ASCOM 6.3.0.2831
Platesolving: PlateSolve 2, failover to local Astrometry.net 0.19 server
Collimation: Metaguide 3, using ASI120MM connected via ZWO Direct Show driver 3.0.0.2

Processing Workflow by Workspace in PixInsight 1.85

1. Calibration
BatchPreProcessing with flats and bias (and master dark with Ha frames), using Cosmetic Correction with master dark.

2. Stack and Mure Denoise
Blink to preview frames and remove some bad images
Image Integration
Mure Noise Reduction on each channel
Channel Combination to merge RGB channels
Dynamic Crop

3. Luminance Linear Processing
Dynamic Background Extraction
Deconvolution, using Dynamic PSF, multiple iterations of Star Mask to create a deringing support image, and stretched luminance as a mask.

4. Luminance Stretching
Histogram Trans
Curves Trans
Noise Reduction with TGV Denoise and Multiscale Median Transform (following David Ault’s Astro Imaging Channel tutorial).
Local Histogram Equalization on galaxy core
Multiscale Median Transform to sharpen core

5. RGB Linear Processing
Dynamic Background Extraction
Photometric Color Calibration
Made second RGB (for star colors only) by deconvolving R and B channels to match FWHM of G

6. RGB Stretching
Histo Trans and Curves Trans
Noise reduction with TGV Denoise and Multiscale Median Transform
Saturation boost with Curves Trans

7. Color Combine
LRGB merge

8. Fixes in Photoshop
Radial blur in color layer on colored halos
Color Select, Minimum Filter to shrink a few large stars
Create artificial flat and subtract to remove background artifacts

9. Final
Mild Multiscale Median Transform to sharpen core
Downsize 50% and save as JPG