Link to RGB image
NGC 7008 (PK 93+5.2, PNG 093.4+05.4) is a 13th magnitude planetary nebula with a diameter of approximately 1 light-year located at a distance of 2800 light years in northern Cygnus. It was discovered by William Herschel in 1787, in Slough, England. I’ve read that the Hubble Space Telescope imaged NGC 7008 in 1995, but I haven’t located that image. The nebula is about 1.4 x 1.1 arc minutes in size.
The Fetus Nebula is an apt description for objects like this, since they’re a large part of the reason we’re here. 98% of the universe is hydrogen and helium, the two simplest elements. But rocky planets like Earth – and the people who live on it – are mostly made of more complex elements, like oxygen, nitrogen and carbon, which were created when stars fused hydrogen and helium into heavier elements. When stars reach the end of their lives, they usually don’t just burn out. If they did, by this point, 14 billion years into its life, our universe would consist of nothing but dead stars, and we wouldn’t be here. Instead, aging stars cast off most of their mass. Huge stars explode as supernovas, but smaller stars like our sun throw off shells of gas, called planetary nebulas (because early astronomers saw these roundish objects in their telescopes and thought they looked like fuzzy planets). So the universe recycles most of its mass, and we get to be here to wonder at it.
Exposure: Total exposure time 18.6 hours, 21:28 x 20 minutes OIII:Ha, 23:23:25 x 2 minutes LRGB. All bin 1x1. Data collected from June to November 2022
Light pollution: SQM ~18.38 (Bortle 7-8, NELM at zenith about 4.5, Red/white zone border.)
Seeing: FWHM of integrated luminance around 2.3 (Ha) and 2.1 (OIII) arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: Full scale.
Equipment:
Scope: C11 (standard, not Edge) with Celestron 0.63 reducer
Mount: Paramount MX+, connected via ASCOM Telescope Driver 6.1 for TheSkyX, with MKS 5000 driver 6.0.0.0
Camera: SXVR-H694, connected via SX ASCOM driver 6.2.1.17140 (SX 1.2.2 also installed)
Filter wheel: Atik EFW2 with 7x1.25 carousel and Artemis 2.4.3.0 driver
Filters: Astrodon Type IIi LRGB
Rotator: Optec Pyxis 2", connected via Andy Galasso's 0.4 driver (Optec Pyxis Rotator AG)
Focuser: Rigel Systems GCUSB nStep motor with driver version 6.0.7 on stock Celestron focuser
OAG: Orion Thin OAG
Guide cam: Lodestar (first generation). 4 second exposures
Automation SW: Sequence Generator Pro 3.1.0.457
Guide SW: PHD 2.6.7, connected to guide cam via native SXV driver
ASCOM: ASCOM 6.3.0.2831
Platesolving: ASTAP, failover to local Astrometry.net 0.19 server
Collimation: Metaguide 3, using ASI120MM connected via ZWO Direct Show driver 3.0.0.2
Processing Software: Pixinisight, Affinity Photo, Photoshop CS2
Processing Workflow by Workspace in PixInsight 1.8.9:
1. Calibration
Calibration with WeightedBatchPreProcessing with flats and bias, using Cosmetic Correction with a master dark
Blink to preview and reject a few frames
Weighting, registration and integration with WBPP
2. Mure Denoise and DBE
Mure Denoise on each channel
RGB Combination for RGB frames
Dynamic Background Extraction
3. Narrowband Linear Processing
BlurXterminator on narrowband. This achieved a better result than deconvolution.
4. Narrowband Stretching
Histo Trans x 2
No Curves Transformation was needed for the narrowband images
5. RGB Linear Processing
ImageSolve
Spectrophotometric Color Calibration, using Average Spiral Galaxy white reference
6. RGB Stretching
BlurXterminator
Histo Trans
Boost color saturation with Curves
Histo Trans
Curves Trans
TGVDenoise
7. Color Combination
PixelMath: Ha for red, OIII for green and blue
Curves Trans to shift nebula toward blue in narrowband image (pulling down green and pulling up blue, while keeping the LRGB balanced)
Combine narrowband and RGB: In Photoshop, I layered the narrowband nebula onto the RGB star field with a mask
8. Final
Final Histogram Transformation
ICC Profile Transform to sRGB
Save as JPG
