Astrophotograph of the Pac-Man Nebula NGC 281

This is my astrophotograph of the Pac-Man Nebula NGC 281, so called because its shape resembles the video game character. It is about 10,000 light years away in the northern constellation of Cassiopeia, where it spans a distance of well over 80 light years. From our perspective, it covers an area about the size of the full moon. This scene shows a small open cluster of stars at the centre, red and blue emission from the nebula’s hydrogen and oxygen atoms respectively, large lanes of dust and dense Bok globules.

This image was made using a quad-band one-shot colour (OSC) filter. This is the first time I’ve used an OSC filter. OSC filters isolate the primary nebulae emission wavelengths. This particular Altair quad-band OSC filter has two “zones”: One zone passes both Hydrogen beta and Oxygen III together, which are captured by the blue and green pixels, and the other passes both Hydrogen alpha and Sulphur III, which are captured by the red pixels. As all other wavelengths are blocked, it is a very effective technique to block out light pollution.

I first photographed the Pac-Man nebula about a year ago in January 2019. There is no comparison!


  • 130× 130-s light frames
  • 32× dark frames
  • 35× flat frames
  • 42× dark flat frames
  • 115× bias frames


  • Explore Scientific ED 102 mm Apo f/7 refractor
  • Sky-Watcher EQ5 PRO SynScan GOTO equatorial mount
  • Altair GPCAM3 290C colour camera (with UVIR window fitted) and 0.5× reducer
  • Altair quad-band one-shot colour (OSC) 2″ filter
  • Altair 60mm guide scope
  • Altair GPCAM2 AR0130 mono guide camera


  • Sharpcap
  • PHD2
  • DeepSkyStacker
  • Photoshop

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