Crescent Nebula (NGC 6888)

[Bill Richards]

I posted this once before, but captured another 11.5 hours of data last week and the new version is (I think) much better.

The Crescent Nebula (aka NGC6888) is an emission nebula about 5000 light-years from Earth. It is formed by the fast stellar wind from a Wolf-Rayet star colliding with and energizing the slower moving wind ejected by the star when it became a red giant 250,000 - 400,000 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.

This is the result of nearly 15 hours of exposure time taken on 2023-07-14, 2023-09-08, and 2026-05-07 through 2026-05-11.

Equipment and Software:
=======================
Mounts: iOption CEM40 w/iPolar and Paramount MX+ Series 6
Telescope: Celestron EdgeHD 8 w/0.7x focal reducer and Astro-Physics AP155 6” refractor
Auto-Focuser: Rigel Systems nFOCUS and Optec FT30 Focuslynx
Imaging Camera: ASI2600MC-Pro and QHY268C
Filter: AstroHutech NBZ dual-band and Radian TriAd Quad
Guide Camera: ASI174MM-Mini on OAG
Imaging Software: NINA
Guiding Software: PHD2
Image Processing Software: PixInsight

Exposure Details:
=================
Camera Temperature -10C
49 x 240s (EdgeHD 8, ASI2600MC-Pro, and AstroHutech NBZ dual-band filter)
139 x 300s (AP155, QHY268C, and Radian TriAd Quad filter)
Plus 32x Darks, Flats, and Dark Flats

#CrescentNebula #NGC6888 #amateurastrophotography #astronomy #astronomyphotography #astrophotography #cosmos #deepsky #deepskyobject #longexposure #nebula #nightphotography #nightsky #outerspace #photography #science #space #spacephotography #stargazing #stars #telescope #universe

 

[JimFox]

Wow Bill! This is really awesome! I don't recall any of that background Ha data in mine. So you really got a lot of great detail in this puppy! I also really like the wispy detail around the brain. That OIII and just all of the incredible detail. This one could be the best we have ever had posted here.

 

[Bill Richards]

Wow Bill! This is really awesome! I don't recall any of that background Ha data in mine. So you really got a lot of great detail in this puppy! I also really like the wispy detail around the brain. That OIII and just all of the incredible detail. This one could be the best we have ever had posted here.

Yeah, that Radian TriAd Quad filter really captures a lot of red since it passes SII as well. The problem with that filter - like many others - is that it generates halos around bright stars. I spent a lot of time trying to eliminate them in post-processing. My Astro Hutech IDAS NBZ filter doesn't have that problem.

Additionally, I integrated multiple nights of images from two different optical trains and two different filters. One was with my ZWO ASI2600MC-Pro camera and the other was with an QHY268C camera. Even though both use the exact same Sony IMX571 sensor, the QHY camera has 4 more pixels on the horizontal axis. PixSinsight's WBPP script wouldn't integrate the two sets because of the two different filters and two different sensor geometries. So I wrote a Java program to change the FILTER keyword value in the FITS header in one set of subs to match the other. Then I had to use PixInsight to crop 4 pixels off all the QHY subs (and masters). Then WBPP was happy to integrate all of them into a single image.

It was a lot of work...