Propeller Nebula, Simeis 57, DWB 111,118,119 (Alastairmk)

Propeller Nebula, Simeis 57, DWB 111,118,119

Simeis 57 is an emission nebula in the hydrogen rich Cygnus X complex. It was first catalogued at the observatory in Simeiz, Crimea, Ukraine in the early 1950s and later by Dickel, Wendker and Bieritz in 1969. My image is still work in progress as I could collect only 13.7 hours of HOS and about an hour of RGB data for stars before the object sunk towards the horizon until next year. Subframes were imaged over 13 nights from early September to the beginning of November, 2022. This object was one of 3 to 4 targets I was imaging at the time and was the first in line for the early evening start when the light pollution is at its worst. The distinctive propeller shape at the centre is somewhat overwhelmed by the surrounding nebulosity in this image. The 60s RGB subs taken to capture the stars made the propeller shape much more distinct.

The NormalizeScaleGradients script in Pixinsight was extremely valuable in getting the light pollution gradients under control. The nebulosity was processed using Ha, SII and OIII starless tone maps that had previously been subject to Mure noise reduction and Deconvolution. These were combined with Pixelmath to give the SII channel (red) a x4 boost and the OII channel (blue) a x6 boost with further noise reduction with TGV and sharpening with MLT. Stretching to non-linear was with a number of GeneralizedHyperbolicStretch operations that also were used to better align colour. A processing challenge was getting a balance between the propeller object and the surrounding background detail. Stars were calibrated with the new SpectrophotometricColorCalibration process and stretched to eliminate the non-stellar background with GeneralizedHyperbolicStretch. They were combined using the inverse of the product of the inverses approach, which worked well.

Light Polluted skies
NOVAC

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Status	Basic success
Started	...
Astrometry.net job	6819383
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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Propeller Nebula, Simeis 57, DWB 111,118,119

Propeller Nebula, Simeis 57, DWB 111,118,119

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Propeller Nebula, Simeis 57, DWB 111,118,119

Propeller Nebula, Simeis 57, DWB 111,118,119

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