| categories:Astrophotography

The Bubble Nebula - NGC 7635 - WIP

Fair amount of integration time on this target, but much of it was taken during high moon illumination (50-70%) and poor seeing/transparency conditions. We don't get a ton of cloud-free nights so I take what I can get :) That said, it resulted in a lot of noise in Sii and to a lesser extent Oiii. I think I pushed the processing a bit much trying to compensate, and not entirely sold on the color combination.

Going to try and get some more signal and try reprocessing in the future.


Bubble is neat target! The “bubble” is sort of the shockwave where the interstellar media and molecular cloud in Cassiopeia are being pushed back by the solar wind of SAO 20575, a bright/hot star (lower right inside the bubble). The Bubble Nebula is ~9000-11000 light years away from us, and the bubble itself is ~7ly across.


  • Ha: 5.7h (143x60s + 43x300s)
  • Sii: 8.5h (94x300s)
  • 7.9Oiii (337x60s @ accidental 2x2bin + 33x300s)


  • ASI1600mm Pro
  • ZWO narrowband filter set
  • Orion 8” f3/9 astrograph
  • AP1100 GTO mount
  • Moonlight focuser
  • ASI120mini and generic 60mm guidescope


  • Bortle 4-4.5 ish
  • Some very high cloud cover, “below average” seeing, “below average” transparency

Pixinsight Processing:

  1. Calibrate, register, SubframeSelector to weight, integrate
  2. DBE
  3. Deconvolution
  4. MedianLinearTransform to target noise in background
  5. Histogram stretch
  6. MedianLinearTransform to enhance sharpness on bubble
  7. PixelMath combination
  8. Curves, Histogram, ColorSaturation fiddling
  9. Star erosion, MLT to smooth over some artifacts
  10. Light TGVDenoise to knock down some more noise
  11. BackgroundEnhance script to pull out a bit more nebulosity
  12. Few rounds of light DarkStructureEnhance
  13. Final curves/histogram tweak
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