Pinwheel Galaxy M101

This beautiful face-on spiral galaxy is known as the Pinwheel Galaxy, or Messier 101. It is enormous at about twice the size of the Milky Way. At a distance of about 21 million light-years, it appears to us as just a little smaller than our moon. If you look carefully, you can see red emission from ionised hydrogen gas in the star forming regions, as well as other distant galaxies in the surrounding area.

This image was predominantly processed in my own astrophotography processing softare, Hera, which is now getting quite powerful. I added finishing touches in Photoshop. I won’t repeat myself here, but I have recently used Hera in various other images, and these posts contain more details. Note though that the software is always developing, and has moved on a lot, even since the most recent of these posts.

Image details


  • 132× 150-s light frames (Gain 900) from 165 overall (best 80%)
  • 5 h 30 min total integrated exposure time from 6 h 53 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
  • 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 0.2.0
  • Photoshop
  • Topaz DeNoise AI (only very little needed)

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