Celestial hemisphere:  Northern  ·  Constellation: Canes Venatici (CVn)  ·  Contains:  M 106  ·  NGC 4226  ·  NGC 4231  ·  NGC 4232  ·  NGC 4248  ·  NGC 4258  ·  PGC 166129  ·  PGC 213962  ·  PGC 2291779  ·  PGC 2292054  ·  PGC 2292458  ·  PGC 2292932  ·  PGC 2294177  ·  PGC 2295162  ·  PGC 2296601  ·  PGC 2297038  ·  PGC 2299019  ·  PGC 2299122  ·  PGC 2299193  ·  PGC 2300116  ·  PGC 2300125  ·  PGC 2300151  ·  PGC 2300712  ·  PGC 2300772  ·  PGC 2832111  ·  PGC 3087510  ·  PGC 3096119  ·  PGC 3096121  ·  PGC 39615
Getting plate-solving status, please wait...
Messier 106 (HaRGB), 


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Messier 106 (HaRGB)

Getting plate-solving status, please wait...
Messier 106 (HaRGB), 


Powered byPixInsight

Messier 106 (HaRGB)

Acquisition details

Dec. 13, 2021 ·  Dec. 14, 2021 ·  Dec. 20, 2021 ·  Dec. 27, 2021 ·  Jan. 6, 2022 ·  Jan. 7, 2022 ·  Jan. 13, 2022 ·  Jan. 17, 2022 ·  Jan. 18, 2022 ·  Jan. 22, 2022 ·  Jan. 26, 2022 ·  Jan. 28, 2022 ·  Jan. 29, 2022 ·  Jan. 30, 2022
Astrodon Gen2 I-Series Tru-Balance Blue: 117×600(19h 30′) -25°C bin 1×1
Astrodon Gen2 I-Series Tru-Balance Green: 84×600(14h) -25°C bin 1×1
Astrodon Gen2 I-Series Tru-Balance Red: 78×600(13h) -25°C bin 1×1
Astrodon H-alpha 5nm: 63×600(10h 30′) -25°C bin 1×1
Avg. Moon age:
16.42 days
Avg. Moon phase:

RA center: 12h18m12s.638

DEC center: +47°1843.85

Pixel scale: 0.834 arcsec/pixel

Orientation: 88.965 degrees

Field radius: 0.490 degrees

WCS transformation: thin plate spline

More info:Open 

Resolution: 3028x2948

File size: 307.9 KB

Locations: Dark Sky Observatory, Fort Davis, TX, United States


Galaxies are humbling experiences. First there is the grandeur of them. There's nothing like a galaxy to make you feel small and insignificant. Then there's the processing.  It took seven tries until I got a result I was happy with but I finally feel like I did some justice to the data.

The major challenge is managing dynamic range. The core and nebulae are bright but the fringes are dim. Normal stretching methods were not able to work for me. I tried the Generalized Hyperbolic Stretch script but I still wasn't able to cope with the dynamic range. That probably says more about me than the script. I suspect in more capable hands it would be up to the task, but I couldn't find a way to do it. Instead I turned to a technique shown at a club meeting by @Randy Lindstrom. This worked out perfectly for this galaxy and also served to help me get the color saturation where I wanted. Essentially it involves alternating high range expansion in HT with a gentle midtone stretch (0.25). Essentially this keeps compressing the high end of the histogram back down toward the center and keeps you from clipping anything that didn't start out clipped. It also includes a color saturation step that helps boost color. I toned down the color boost from Randy's example. On this image it felt unnatural but the idea really does help keep color while stretching. UPDATE: In revision B I was able to do the stretch entirely in GHS.

I also ended up doing a background neutralization/color calibration rather than a photometric color calibration step because PCC just didn't do a good job on the galaxy. It left things looking reddish and a bit muddy. The old school BN/CC steps saved the day for this one.

Here was the workflow:

pixelmath h - r*scale

pixelmath r+(h-med(h))*scale. (masked with copy of H that was stretched and manipulated to increase contrast)

channel combination
dynamic crop
GHS (final stretch)
HDRMT (heavy mask)
LHE (heavy mask)
MLT (sharpening, heavy mask)
pixel math in stars (screen)

GHS (minor inverted stretch)
unsharp mask (very mild sharpening)

Original Version:
channel combination
dynamic crop
MLT noise reduction
background neutralization
color calibration
HT high range expansion (1.3)
color saturation
HT high range expansion (1.2)
HT midtown stretch (.25)
alternated high range expansion/midtone stretch until the image was where I wanted
HDR multiscale transform
NRGBCombination in H
Curves (slight color boost)
EZ Star Reduction script
MLT Sharpening
in photoshop:
color range selection on galaxy core
hue adjustment to bring the core more toward yellow from the salmon it had become
add a bit of vibrance in adobe camera raw filter
and then back in PI
SCNR to gett some green tint out of the core

While M106 is the focus of the image I decided to crop to leave in a lot of the nearby galaxies. I was back and forth on this until the last minute but ultimately decided to leave the neighbors in.

I want to thank John Kasianowicz and Christoph Bertsch for making this opportunity available to me. The chance to use great equipment in a dark sky is a joy!



  • Messier 106 (HaRGB), 


  • Final
    Messier 106 (HaRGB), 




Description: Reprocessed with BlurXterminator and used a different method to combine H with RGB.

Uploaded: ...

Sky plot

Sky plot


Messier 106 (HaRGB),