NGC6888 in Ha


The Crescent Nebula lies about 2 degrees south of Sadr in the constellation of Cygnus, and is estimated to be approximately 5000 ly away. This rendition was taken on the night of 24th October with a Baader 7nm Ha filter, and is a result of stacking 9×15 minute exposures with a SX-VR H36 camera through a Pentax 75 telescope. Guiding was undertaken with an SX lodestar and SX-AO unit. Image was calibrated using Darks, bias, flats and dark flats. Stacking software was DSS.

Picture saved with settings applied.

The Crescent Nebula was 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 resulting in 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. The star at the centre of the Crescent Nebula sheds mass at a tremendous rate, close to a full solar mass in just 10,000 years.

Rework of the image after adding better calibration images, which has allowed the fainter nebulosity to be drawn out.


Thanks for looking, Steve