- L440 minutes (47 frames)
- O210 minutes (42 frames)
- B20 minutes (4 frames)
- H240 minutes (46 frames)
- R30 minutes (6 frames)
- G30 minutes (6 frames)
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.
| Photo | Date | Frames | Exposure | L | R | G | B | H | O |
|---|---|---|---|---|---|---|---|---|---|
 | 16 Apr 2021 | 73 | 06:05 | 00:30 | 00:30 | 00:30 | 00:20 | 02:25 | 01:50 |
 | 21 Feb 2021 | 69 | 05:45 | 00:30 | 00:30 | 00:30 | 02:25 | 01:50 | |
 | 04 Jan 2021 | 73 | 06:05 | 00:30 | 00:30 | 00:30 | 00:20 | 02:25 | 01:50 |
 | 04 Jun 2019 | 12 | 01:00 | 00:30 | 00:30 |
Visibility chart of Crescent Nebula (NGC 6888) during the day
| Date | Moon Phase | Exposure | CCD Temperature | Gain | Offset | Filter |
|---|---|---|---|---|---|---|
- 2023ixf•
- 40 Eri•
- Abell 74•
- Artemis A868 SA•
- a Canis Minoris•
- C 2020 R4 ATLAS•
- C 2020 T2 Palomar•
- C 2021 S3 (PANSTARRS)•
- Haumea (2003 EL61)•
- HCG 68•
- HCG 92•
- IC 1318B•
- IC 1396•
- IC 1795•
- IC 1805•
- IC 1848•
- IC 1871•
- IC 3322A•
- IC 342•
- IC 4015•
- IC 405•
- IC 417•
- IC 434•
- IC 443•
- IC 4703•
- IC 5070•
- IC 5146•
- IC 63•
- M 1•
- M 101•
- M 103•
- M 109•
- M 13•
- M 15•
- M 27•
- M 3•
- M 33•
- M 42•
- M 45•
- M 5•
- M 51•
- M 57•
- M 63•
- M 64•
- M 74•
- M 76•
- M 81•
- M 82•
- M 86•
- M 87•
- M 94•
- M 97•
- NGC 147•
- NGC 1491•
- NGC 1499•
- NGC 1579•
- NGC 1961•
- NGC 2146•
- NGC 2239•
- NGC 2403•
- NGC 281•
- NGC 4236•
- NGC 4565•
- NGC 4631•
- NGC 507•
- NGC 508•
- NGC 5866•
- NGC 5907•
- NGC 6503•
- NGC 6823•
- NGC 6888•
- NGC 6946•
- NGC 6992•
- NGC 6995•
- NGC 7000•
- NGC 7023•
- NGC 7129•
- NGC 7217•
- NGC 7331•
- NGC 7380•
- NGC 7538•
- NGC 7635•
- NGC 7640•
- NGC 7822•
- NGC 891•
- NGC 896•
- NGC 925•
- PGC 54559•
- Sh2-155•
- Sh2-168•
- Sh2 103•
- Sh2 109•
- Sh2 132•
- T CrB•
- UGC 6930•
- V1405 Cas•
- Vesta A807 FA•