Shot on 23 Feb 20265 photosNGC 6888
Crescent Nebula
- Right ascension
- 20ʰ 12ᵐ 13ˢ
- Declination
- +38° 23′
- Constellation
- Cygnus
- Tonight
- Never sets
- yes, circumpolar
- total exposure
- 16 h 10 min
- frames in the FITS archive
- 151
- imaging nights
- 9
- imaging period: 27 May — 29 May
- 2020–2024
Visibility and signal
Exposure by filter
- L7 h 20 min · 47 frames
- R30 min · 6 frames
- G30 min · 6 frames
- B20 min · 4 frames
- Hα4 h · 46 frames
- OIII3 h 30 min · 42 frames
Share of each filter in the total exposure
- Narrowband filters
- 46%needs a dark sky
- Typical frame
- 385 s151 frames in total
- In one night
- 1 h 48 minaveraged over 9 nights
Altitude above the horizon tonight
Observing log9 nights · 151 frames
Photos of the objectEach photo is a separate processing; parameters and equipment are on the photo page
About the object
The Crescent Nebula (NGC 6888), also known as the Half Moon Nebula or Caldwell 27, is a cosmic bubble about 25 light-years across, formed by a strong stellar wind from a bright central star. This star, known as a Wolf-Rayet star (WR 136), is blowing off its outer shell with an intense stellar wind, ejecting a mass equivalent to that of the Sun every 10,000 years.
The nebula's complex structure is the result of the interaction of the strong wind with material ejected by the star during earlier stages of its evolution. The star is actively burning nuclear fuel and is approaching the end of its life, which will lead to its explosion as a supernova. The Crescent Nebula is located in the constellation Cygnus, about 5,000 light-years** from Earth.
The nebula was discovered by William Herschel in 1792, but since then significant improvements in astronomical technology have allowed scientists to realize that the "milk ray" observed by Herschel is actually part of a larger oval structure. At the center of the nebula is the star WR 136, which is one of the hottest stars in the Universe, 21 times more massive and 60,000 times brighter than the Sun.
The Crescent Nebula is classified as an emission nebula, as its light comes from the star at its center, rather than from the reflection of light from other stars. WR 136 is expected to end its life in a bright supernova explosion.