Sunday, September 30, 2018

IC 5146 - The Cocoon Nebula


The Cocoon Nebula is an emission and reflection nebula in Cygnus. It is 4000 light years away and spans 15 light years across (it has a visible size of 12 arc minutes - the full moon is 31 arc minutes).
(click image for full resolution image)

The brightest (red) parts of the nebula is the emission part - the darker parts with the blue hue are illuminated by the central star with the unassuming name "BD +46°3474". It's a very young star (~100,000 years!), it is 5 times larger than the sun, has 15 times the mass of the sun and shines 20,000(!!) times brighter!!! The nebula is very young - many stars are still "pre-sequence" stars (i.e. they are not shining visibly yet).

Processing this image was challenging because of the bright emission parts and the darker dust lanes around it. In my initial attempt, I focused too much on the bright, red part and its details and cut out almost all of the dust lanes:

I found it surprisingly difficult to process this image better. In order to do that, I tried out a couple of new things:

  1. Using the NBRGBCombination script in Pixinsight
  2. Carefully adjusting color levels using CurvesTransformation to bring out the red in the core and the blue in the faint regions
  3. Using a very fuzzy mask for processing the core that slowly increases protection over the faint, outer layers.

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