NGC 6888

It is a Crescent Emission Nebula located in the constellation Cygnus. Its shape is due to the stellar wind of the star WR 136 which, due to its instability as it is at the end of its life, ejects its matter. The star should explode in a supernova in about 100,000 years.

The star, of the Wolf-Rayet type as in the case of the Bubble Nebula, is hot and massive. However, it has reached the end of its life stage and has started to reach the end of its main fuel which is hydrogen. While its core and its outer layers were in equilibrium until then, the fact that it has exhausted its hydrogen has reduced its gravitational attraction. The latter then becomes too weak to retain the outer layers which are expelled by the stellar wind. This is what creates this particular and very recognizable shape around the star.

It is named after its crescent shape, corresponding to the vertical envelope to the left of the nebula, when observed or photographed without a filter. We do not then perceive all the complexity of the gases surrounding it and rather give it a brain shape.

The image presented is the result of an L-Ultimate filter to extract hydrogen (Ha) and oxygen (OIII). The oxygen layer is particularly delicate to treat since it surrounds everything. It is therefore necessary to use different masks to bring out all the details.

Equipment used:
- Skywatcher 80ed Evostar
- ZWO 533mc pro
- ZWO 120mm mini
- EQM-35 Pro
- Asiair plus
- EFW
- EAF
- OAG
- L-eXtreme filter
- Stacked and Ha/OIII extracted with Siril
- Processed with PixInsight
- Finished with Lightroom