NGC6888 - Crescent Nebula (David Foust)

NGC6888 - Crescent Nebula

Link: https://www.davidfoust.com/gallery/ngc6888-crescent-nebula

This is another new target for me, as it is relatively small and the resolution of my telescope and camera combination is generally undersampled, so it is difficult to resolve much detail within the Crescent itself. On top of all of that, I am evaluating purchasing PixInsight, which is sort of the “industry standard” program for astrophotography these days, as there are many more tools available for processing. It has an incredibly steep learning curve, but with a little time an patience, I’m starting to get better results than what I was previously achieving with Siril. At the end of the day though, I am still somewhat limited by my overall data quality (i.e. undersampling). The Crescent is a commonly imaged target in the constellation Cygnus, and I was able to gather about 13h of data over three nights. I split each session between two targets (Crescent and M31) because the Crescent Nebula drops fairly quickly under 45 degrees in the western sky this time of year (after about 4 hours or so), and I didn’t want to waste any imaging time over a clear night. I should also note that the two most recent nights (Sep 17/18) were under more or less a full moon. Imaging under a full moon is challenging and less than ideal (but not impossible). Many imagers use narrowband filters to reject light pollution and moon glow to make the most of their imaging time. I may consider a dual-narrowband filter for moon-filled nights. The level of signal to noise in each subframe was noticeably different between the moonless and moon-filled nights. Nonetheless, I’m overall pretty happy with the result.

The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5,000 light-years away. 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 years ago.

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Description: Completely reprocessed in PixInsight.

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