The Andromeda Galaxy

July 2022 Reprocess

Original September 2019 edit

Image Details:

Andromeda is the closest spiral galaxy to our Milky Way at a distance of 2.5 million light years, and is best seen and photographed during Autumn while it is highest in the sky. From even moderately dark locations this galaxy is visible as a dim smudge in the sky to the naked eye and it actually fills an area of sky over 6 times the apparent width of a Full Moon. Telescopes of sufficient aperture can also reveal some of the dark nebula bands running across the brighter galactic core.

Andromeda is approaching us at ~110 kilometers per second, and should begin merging with our galaxy in roughly 5 billion years. This island universe hosts an approximate one trillion stars and is similar in size as the Milky Way at 200,000 lightyears in diameter.

I photographed this galaxy during September 2019 from 3 locations in 2 states, including 2 dark sites, as a 2-panel mosaic. Hα was included to highlight HII regions which are forming new stars

July 2022 Notes:

In the original edit I spent significant time making selective color tweaks to bring out the blue haze surrounding the galaxy which was seemingly and frustratingly missing. Numerous other images of M31 available online which showed the blue color on the outer edges so I was unsure why it was so difficult to" “find” in my own data, particularly since the color was captured from rather dark skies absent any significant contribution from light pollution. Since this time I’ve learned more about the cosmos - particularly that O and B-class stars (meaning hotter Blue-colored stars) make up barely 1% of average stellar populations, so in this newer edit I simply exaggerated the color already present. The result is a photo of much warmer color, though not without some cooler regions in areas of stellar creation (notably including the NGC 206 cluster on the left side).

I also blended the Hα data into both the Red and Blue channels this time. While my filter only captures the stronger (Red) Hα line, blending this data at reduced intensity into the Blue channel can help simulate the other Hydrogen emission lines of the Balmer series. These can be seen as the ring of pink~ish spots dotting Andromeda’s “nuclear ring.”

Equipment:

  • William Optics Star71-II Petzval APO (345mm Focal Length, F/4.9)

  • ZWO ASI1600MM-P, ZWO Filters

  • Celestron CGEM-II

  • Autoguiding: Orion 50mm Guidescope + ZWO ASI224MC

Exposures:

  • Luminance: 136 x 240”, 184 x 120” (Total: 15h 16m)

  • Red, Green, Blue: 68, 68, 68 x 240” (Total: 13h 40m)

  • Hydrogen-Alpha 7nm: 192 x 300” (Total: 8h)

Misc Details:

  • Capture Software: AstrophotographyTool, PHD2 (guiding), Celestron CPWI (mount control), Pegasus Powerbox (dew heater control, power management)

  • Processing Software: PixInsight, Photoshop

  • Taken from: Fall River KS (Bortle 2), Okie-Tex Star Party 2019 (Bortle 1), Wichita, KS (Bortle 5)

  • Capture Dates: 1-6, 22 September 2019

Annotation