The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by William Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000[citation needed] years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.
Visibility
The Crescent Nebula is a rather small object located about 2 degrees Southwest of Sadr. While considered bright by astronomical imaging standards, visually it is relatively faint. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or a Euro sign shape which makes some call it the "Euro sign nebula"
Image Session Details
-Location: 50.23°N, 8.46°E
-Target: NGC 6888 – Crescent Nebula
-Integration: 50 × 180s = 2h 30m
-Camera: Nikon D3500 (APS-C DSLR) – ISO 400
-Telescope: Askar 103 APO + 0.8× reducer (576 mm)
-Mount: Bresser Exos-2 + OnStep
-Control: ASIAIR Mini
-Guiding: SVBONY SV165 + ASI120MM Mini
-Sky Quality: Bortle 4, SQM ~20.8
-Moon Phase: Full Moon (100%)
-Filter: None (stock DSLR)
-Date: 11 June 2025
-Object Type: Emission Nebula (Wolf-Rayet bubble)
-Constellation: Cygnus
-Apparent Size: ~20′ × 10′
-Distance: ~4,700 light years
General Properties
Coordinates: 20h 12m 07s, +38° 21′ 18″ (J2000)
Apparent Magnitude: 7.4
Angular Size: 18′ × 12′
Distance: ~1.45 kpc (≈4,700 ly)
Constellation: Cygnus
Scientific Databases
[ POSITION ]
RA: 283.396237°
Dec: +33.029134°
Parallax: 1.270 mas
Proper motion: pmRA=1.65 mas/yr, pmDEC=2.47 mas/yr
Redshift: -6.4e-05
Radial velocity: -19.1 km/s
[ POSITION ]
RA: 303.027258°
Dec: +38.354940°
Parallax: 0.577 mas
Proper motion: pmRA=-7.90 mas/yr, pmDEC=-6.68 mas/yr
Redshift: -0.000334
Radial velocity: -100.0 km/s
[ PHOTOMETRY ]
Catalog: V=7.50, G=7.20, B=7.49
V: 7.50
B: 7.49
B–V: -0.01
Hubble type (from color): Irr
IRAS 12 µm: 0.45 Jy
IRAS 25 µm: 0.46 Jy
IRAS 60 µm: 7.11 Jy
IRAS 100 µm: 98.20 Jy
1.4 GHz flux: 0.00 Jy
[ DISTANCE ]
1732.38 pc (5.65 kly, Gaia proxy (hot-star parallax))
[ PROVENANCE ]
Gaia DR3: source_id 2061690233159124352, G=7.20, BP−RP=0.58, π=0.577±0.016 mas
[ ALIASES ]
Crescent Nebula, 2MASS J20120654+3821178, HD 192163, HIP 99546, IRAS 20102+3812, LBN 075.51+02.29, LBN 203, NGC 6888
-NED
Observation Notes
-Photographic Magnitude:10
