NGC 6888: The Crescent Nebula

This is another image from telescope live: the Crescent Nebula. It was a tough dataset to stack, as there were a bunch of dead pixel lines from the CCD. However, once the dataset was stacked, it was quite fun to process. The Oiii data was extremally strong, and it was really interesting to see the extent of the wispiness around the nebula. I’ve been experimenting with a new “natural” pallete made from SHO emissions, and I think it turned out pretty accurate!

NGC 6888, also known as the Crescent Nebula, is a cosmic bubble about 25 light-years across, blown by winds from its central, bright, massive star. It combines a composite color image with narrow band data that isolates light from hydrogen and oxygen atoms in the wind-blown nebula. The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. NGC 6888’s central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun’s mass every 10,000 years. The nebula’s complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

Image:

Full-quality image here: https://live.staticflickr.com/65535/52862198723_de73d2bef9_o.png

Details:

Telescope: Officina Stellare 700 RC
Camera: FLI PL16803
Filters: Halpha, SII, OIII,
Location: IC Astronomy, Oria, Almería, Spain
Date of Observations: 8/28/2022, 8/29/2022, 9/1/2022, 9/14/2022
Sii: 12 x 600s (2h)
Ha: 12 x 600s (2h)
Oiii: 12 x 600s (2h)
Processing: Pixinsight
Credits: Data: Telescope Live; Processing: William Ostling

Processing:

Processing:
- Images were cosmetic corrected for hot pixels
- The subframes were weighted, registered, normalized, integrated, and drizzled in WBPP
Preparation of all frames:
- Stacking artifacts were cropped
- SHO were combined to create an RGB image
- RGB image was plate solved
- Starless DBE was applied to RGB as follows:
      - Starnet 2 was applied to a clone of the target image, creating an image with stars and an image without stars
      - DBE was applied on the starless image to create a background model
      - The background model was subtracted from the stars image
Deconvolution of the RGB
- a PSF was created using the dynamic PSF process
- Linear starnet was applied to create a starless image and a star mask
- the linear image was duplicated, stretched, clipped, and convoluted to create a mask
- The starless image was deconvoluted using the RVC algorithm
- the stars were added back in
- DeepSNR noise reduction was applied to RGB
- A natural pallete was created from the SHO palleete
Non-linear Adjustments
- Initial GHS stretch
- Targeted GHS + MMT division for color balance
- Noise reduction
- Curves transformation
- Color Calibration