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Contains:  M 31, Great Nebula in Andromeda, NGC 224, M 32, NGC 221, M 110, NGC 205
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M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah
M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah

M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project

Technical card

Resolution: 4400x3500

Dates:Oct. 26, 2019Oct. 27, 2019Oct. 28, 2019Oct. 29, 2019Oct. 30, 2019Oct. 31, 2019Nov. 1, 2019

Frames:
Astrodon Gen2E B: 90x120" -35C bin 1x1
Astrodon Gen2E G: 90x120" -35C bin 1x1
Astrodon Gen2E L: 300x60" -35C bin 1x1
Astrodon Gen2E R: 90x120" -35C bin 1x1

Integration: 14.0 hours

Avg. Moon age: 9.87 days

Avg. Moon phase: 7.28%

Astrometry.net job: 3042219

RA center: 0h 42' 44"

DEC center: +41° 16' 4"

Pixel scale: 2.331 arcsec/pixel

Orientation: 269.891 degrees

Field radius: 1.820

Locations: Ben's Backyard, Federal Way, WA, United States

Data source: Backyard

Description

M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project

I keep coming back to M31, the Andromeda Galaxy, mainly because it's such a large, iconic target, but also because it allows me to comparatively try out different hardware and acquisition and processing steps. This time around I purposely targeted shorter exposure times than I have done in the past in order to try not to oversaturate the foreground stars.

I will forgo my usual long physical description of this target given that it's already so well known and documented. If you are interested in one of my past write-ups, please refer to my description from an earlier image from over a year ago. To my eye now that image is a boring brown that holds little interest. And then I must have revisited it last December with this overly processed, overly blue specimen. I hope you find my latest one an improvement.

Using the typical SNR equations and going for a read noise contribution of < 5%, I arrived at 60s exposures for the L filter, 120s exposures for the RGB filters. Overall I like this result and enjoyed processing so many different frames. For the final combined image I ended up using (L,R,G,B) = (300,90,90,90) frames x (60,120,120,120) s = (5,3,3,3) hrs of integration time.

In processing, I did apply denoising steps, first with the MureDenoise script in PixInsight, later with TGVDenoise in the nonlinear phase. Not surprisingly, Deconvolution was not effective at this large image scale, nor was sharpening, so neither was done in the end.

For color calibration, I started with the PhotometricColorCalibration process, however I found that my usually preferred setting on G2V resulted in a rather boring, odd yellow-orange galaxy that held little interest to me. I decided to tweak the PCC parameter to K2V, and this yielded an interesting yellowish core with faint blue outer regions. I then was quite liberal with color saturation using CurvesTransformation (perhaps a bit too heavy handed), however my wife, who is often a harsh critic of my images, liked it, so there. No more discussion will be tolerated on the matter.

What I like about having pushed the saturation a bit is that, having only used broadband red, I can see prominent Ha regions along the rim of the galaxy. These would be nicely enhanced with added Ha data, but I have not gotten in the habit of doing that. It might be nice to add that into this image in the future.

Thank you for your attention, and as always, your comments, critique and suggestions are always welcome. (I was just kidding that no more discussion would be tolerated - I actually encourage and welcome it!)

Comments

Author

BenKolt
Ben Koltenbah
License: None (All rights reserved)
3888
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Revisions

  • Final
    M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah
    Original
  • M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah
    B
  • M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah
    C
  • M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah
    D

B

Luminance Image

C

Inverted Luminance Image

D

Annotated LRGB Image

Sky plot

Sky plot

Histogram

M31 Andromeda Galaxy (And) in LRGB - Short Exposure Project, 





    
        

            Ben Koltenbah