Veil Nebula (HOO)

Veil Nebula (HOO)

The Veil Nebula, also known as Cygnus Loop, is a large nebulous field in the constellation of Cygnus. It consists out of 3 major distinctive elements: the Eastern Veil (to the left), Western Veil (to the right) and the Pickering’s Triangle (between the two veils). The veil is a supernova remnant from a supernova that occurred at some time between 5000 to 8000 years ago. It is suspected that the distance to the nebula is around 1470 light years.

With a relatively high average apparent magnitude of 7 you might think that this is a very bright nebula, but it absolutely isn’t. That is due to the whole radius of that complex is around 50 light years and it spans around 3 degrees in visible diameter. The Veil can be observed by eye surprisingly well with larger telescopes (10″ and up) and OIII filters, despite its dim brightness.

Technical Details

First mosaic! Woo! This took me way more effort than I actually thought it would be. I captured this image over 5 nights, where one was almost gone to waste completely due to rotation of the camera. Also because of bad planning of the mosaic. Well, it was my first attempt of doing so and I think I succeeded.

It’s by far not perfect and could benefit from even more integration time and a better planning of the mosaic itself. It also could benefit from getting rid of all tilt in my image train and the OIII data captured exclusively on a moonless night, which I didn’t do. What I also found is that my focuser tends to drift over night, giving me worse frames at the end than what I had at the start. I need some way to properly fix it. Maybe replace the focuser? Something to think about in the future.

Overall, I’m very happy with how this image turned out to be after all. For a first mosaic try it came out way better than I could have hoped for.

Acquisition Details

Shot with Atik 383L+ on TS Optics 70mm f/6 FPL53 APO Triplet

Dates: 2018-07-31, 2018-08-02, 2018-08-03, 2018-08-04, 2018-08-11
H-Alpha Western Veil: 29×15m 1×1 binned
H-Alpha Eastern Veil: 23×15m 1×1 binned
OIII Western Veil: 20×15min 1×1 binned
OIII Eastern Veil: 23×15m 1×1 binned

Postprocessing Details

Ha Mosaic

  • LinearFit to OIII

OIII Mosaic

  • StarAlign to Ha

HOO Combination (R=Ha, G=0.5×Ha+0.5×OIII, B=OIII)

L (Extracted from HOO)

  • Deconvolution
  • TGVDenoise
  • MultiscaleMedianTransform
  • HistogramTransformation (Midshift to left, expand highlights)
  • HistogramTransformation (Black and Whitepoint to 0, more stretching)
  • HDRMultiScaletransform (6 layers, contrast adjustment)
  • LocalHistogramTransformation (Kernel 128, Contrast 1.5, Amount 0.5)
  • MorphologicalTransformation (Star size reduction)
  • MultiscaleMedianTransform (Sharpening)
  • CurvesTransformation (Reduce contrast of Nebulosity)
  • CurvesTransformation (Adjust contrast of whole image)


  • ABE
  • LinearFit RGB channels to R
  • SCNR
  • ArcSinhStretch (500)
  • HistogramTransformation
  • LRGBCombination (0.5 Lightness, 0.4 Saturation)
  • ColorSaturation (Teals)
  • CurvesTransformation (Saturation)
  • CurvesTransformation (Yellow shift to Orange/Gold)

Annotated Image


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