Andromeda Galaxy M31

This is the Andromeda Galaxy M31, the most distant object that can be seen by the naked eye. It’s the Milky Way’s nearest neighbour at about 2.5 million light-years from Earth. And it’s about twice the size of the Milky Way at about 200,000 light-years across.

YouTube “short”

This “short” on YouTube shows the stages of processing, which was almost completely carried out in my astrophotography processing software, Hera.

The image was taken using a quad-band filter. This was a mistake—it’s not usual to use a filter like this on galaxies, but it doesn’t seem to have affected the final result too badly.

Image details


  • 55× 150-s light frames (Gain 900) from 68 overall (best 80%)
  • 2 h 70 min 30 s total integrated exposure time from 2 h 50 min overall (best 80%)
  • Full use of calibration frames (darks, flats, dark flats)


  • Explore Scientific ED 102 mm Apo f/7 refractor
  • Revelation Adjustable Field Flattener
  • Sky-Watcher EQ6-R PRO SynScan GOTO equatorial mount
  • Altair Hypercam 294C PRO colour fan-cooled camera
  • Altair quad-band one-shot colour (OSC) 2″ filter
  • Pegasus FocusCube v2
  • Altair 60mm guide scope
  • Altair GPCAM2 AR0130 mono guide camera
  • Hystou Rugged Fanless Mini PC i5 7260U


  • SharpCap 4.0
  • PHD2
  • DeepSkyStacker
  • Hera 0.3
  • Photoshop
    • “Local contrast enhancement” from Astronomy Actions Tools
    • “Enhance dust lanes” from Annie’s Actions
  • Topaz DeNoise AI for almost negligible sharpening

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