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Messier 31: The Andromeda Galaxy - 20200127 Dataset

August 26, 2020

Full Resolution Image

Messier 31, better known as the Andromeda Galaxy, is a large spiral galaxy located in the Andromeda Constellation. At an estimated distance of 2.537 million light years, Messier 31 is the nearest major galaxy to our own and appears to be on a collision course with our home galaxy, the Milky Way. This collision would result in a new galaxy called Milkdromeda. With an estimated star count of 1 trillion, this collision would result in a combined galaxy of 2.25 trillion stars. Fascinating Stuff!!

Messier 31 has many know designations, but the following are the most known: Andromeda Galaxy, Andromeda Nebula, M31 (Messier 31), and NGC224 (New General Catalog). The Andromeda Galaxy was named after the area of earth's sky that it occupies, the Andromeda Constellation, which in turn represents the princess Andromeda in Greek Mythology. Andromeda was chained to a rock and left to a sea monster to appease Poseidon after her mother Cassiopeia had boasted that her daughter’s beauty surpassed that of the sea nymphs. The princess was saved by Perseus, the Greek hero represented by the neighboring constellation. Interestingly, 2 of the neighboring Constellations to the Andromeda Constellations are the Cassiopeia Constellation, and the Perseus Constellation.

The Andromeda Galaxy has a total of 14 satellite galaxies, of which Messier 32 and Messier 110 are visible in this image. These are marked in the Annotated image below.

Full Resolution Annotated Image

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I am currently facing some seriously unfortunate weather, so, I have decided to reprocess ALL (only exception is for what I consider completely unusable data) of my old data. The goal of this is to see how much I have improved, actually finish some old projects, and continue practicing my processing techniques. All of my equipment, used software, and processing techniques will be listed below. This image in particular is my fourth attempt ever at Astrophotography. Previous attempts include the dates of 2020-01-22, 2020-01-24, and 2020-01-25. Reason for discarding the data on those days include really bad focus, and terrible tracking leading to blurry/streaky images.


  • Nikon D7500
  • Nikon 85mm f/1.8G
  • NyxTech Barn Door Tracker
  • Software:
    • DeepSkyStacker
    • Adobe Photoshop
    • RC Astro GradientXTerminator Plugin for Adobe Photoshop
    • Noel Carboni's Astro Tools Plugin for Photoshop
    • Adobe Lightroom
    • AstroBin for Annotated SVG File (PixInsight)

Data was acquired on the night of 2020-01-27.

  • RGGB
    • 35 Total Exposures
    • 20 Second Individual Exposure Length
    • f/2.8
    • ISO 3200
    • Dark Frames
      • 47 Total
    • Flat Frames
      • 44 Total
    • Bias Frames
      • 40 Total
  • Total Integration Time
    • 11 Minutes and 40 Seconds (700 Total Seconds)
  • Location
    • Backyard: Comer, Georgia
    • 34°03'49"N 83°07'31"W (Closest Town)
    • Bortle Class 4
  • Weather
    • Average Moon Age at 2.41 Days
    • Average Moon Phase at 6.42%
    • Clear Skies

Image was Stacked and Calibrated in DeepSkyStacker. These were the settings:

  • Result
    • Standard Mode
    • No Drizzle
    • No Align RGB Channels
  • Light
    • Kappa-Sigma clipping
    • Kappa: 2.00
    • Number of iterations: 5
  • Dark
    • Median Kapp-Sigma clipping
    • Kappa: 2.00
    • Number of iterations: 5
    • Hot Pixels detection and removal
  • Flat
    • Median Kapp-Sigma clipping
    • Kappa: 2.00
    • Number of iterations: 5
  • Bias
    • Median Kapp-Sigma clipping
    • Kappa: 2.00
    • Number of iterations: 5
  • Alignment
    • Automatic

Image was then opened in Photoshop for the following:

  • Convert to 16 Bit's/Channel using Exposure and Gamma
  • Selected a spot near Messier 31 with the Color Sampler Tool
  • Levels Adjustment to balance Black Point
    • Goal: 45, 45, 45
    • Black Point Adjustments: 16, 6, 0
  • Astro Tool's Deep Space Noise Reduction
    • This data was very noisy. While not noticeable at this stage, it would have been impossible to remove once I began stretching the data.
    • Pros for doing this now: Less Noise to deal with later
    • Cons for doing this now: Slight Loss of Data. Image becomes more "fuzzy".
  • Astro Tool's Space Noise Reduction
    • Same Note as above.
  • Curves
    • Input 57, Output 132
    • Input 113, Output 196
  • Levels Adjustment to balance Black Point
    • Goal: 55, 55, 55
    • Black Point Adjustments: 70, 70, 70
  • Curves
    • Input 88, Output 143
  • Used Lasso Tool to select area around Messier 31. Then inverted the Selection.
  • GradientXTerminate
    • Detail: Medium
    • Aggressiveness: Medium
    • Balance background color: Checked
  • GradientXTerminate
    • Detail: Fine
    • Aggressiveness: High
    • Balance background color: Checked
    • Both GradientXTerminate Operations helped remove a very obvious gradient that had formed from the bottom left corner, all the way up to the top right corner.
  • Levels Adjustment to balance Black Point
    • Goal: 35, 35, 35
    • Black Point Adjustments: 68, 68, 66
  • Cropped to fit in 16:9 Image Ratio
    • This removed some stacking errors as well as helped in better framing the target.
  • Saved

Image was then opened in Lightroom for the following:

  • Created Selective Mask over Messier 31
    • Saturation set to +100
    • This effect was very subtle, and I really enjoyed it.
  • Saved

Image was then opened in Photoshop again for the following:

  • Astro Tool's Reduce Large Blue/Violet Halos
    • This removes some of the Blue/Violet Halos that had come up with the stretching and the Saturation Boost.
  • Saved and Done!

For those that read this far, THANK YOU! Please let me know how if you have any questions, or if there is something I can improve upon.