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Contains:  Crescent nebula, NGC 6888
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NGC 6888 - Crescent Nebula HOO (2019) & Soap Bubble, 


            Kurt Zeppetello
NGC 6888 - Crescent Nebula HOO (2019) & Soap Bubble
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NGC 6888 - Crescent Nebula HOO (2019) & Soap Bubble

Technical card

Dates:July 13, 2019July 14, 2019July 30, 2019Aug. 9, 2019Aug. 11, 2019

ZWO Ha 7nm 1.25": 59x180" (gain: 139.00) -10C bin 1x1
ZWO O-III 7nm 1.25": 97x180" (gain: 139.00) -10C bin 1x1

Integration: 7.8 hours

Darks: ~12

Flats: ~15

Bias: ~20

Avg. Moon age: 14.38 days

Avg. Moon phase: 68.08%

Bortle Dark-Sky Scale: 5.00

Temperature: 16.00

Basic astrometry details job: 2866307

RA center: 20h 12' 1"

DEC center: +38° 21' 46"

Pixel scale: 1.204 arcsec/pixel

Orientation: 173.147 degrees

Field radius: 0.942 degrees

Resolution: 4542x3336

Locations: Happy Frog Observatory, Monroe, Connecticut, United States

Data source: Backyard


Thanks to Luca Marinelli for pointing out the Soap Bubble Nebula (PN G75.5+1.7) on right side.

The Crescent Nebula (NGC 6888) is a massive bubble 25 light-years across and approximately 5000 light-years away in the constellation Cygnus. This object is the result of the collision of faster moving stellar wind from a Wolf-Rayet star (a star that lost its outer hydrogen layer) colliding with and energizing slower moving wind ejected by the star when it became a red giant sometime around 250,000 to 400,000 years ago. The star known as WR136 is near the end of its stellar life and will probably go out in a supernova most likely not in our lifetime though. It is the bright yellowish star near the center of the Crescent.

I captured this object almost exactly two years ago with my old setup and using a UHC filter. For what I had it was OK but I really wanted to capture the blue-green hue of the oxygen mingling with the red hydrogen I had to wait until now. I obtained about 3 hours of Ha and 5 hours of OIII to ensure there was enough to produce the HOO image. I thought I was going to crop it more but I really liked the nebulosity so I kept it wide field. Additionally, I reduced the stars a bit more than I usually do because I wanted to highlight the surrounding nebulosity especially in the lower left where they almost look like wave fronts. Lastly, after many test adjustments, I did not darken the background too much liked the faint red-blue hue of the surrounding nebulosity.

Link to Video of Capturing and Processing:

Link to Video of Capturing and Processing



Kurt Zeppetello
License: None (All rights reserved)

Sky plot

Sky plot


NGC 6888 - Crescent Nebula HOO (2019) & Soap Bubble, 


            Kurt Zeppetello

In these public groups

Imaged with APT