NGC 7652 in Cassiopeia

The Bubble Nebula is a Wolf-Rayet bubble, formed by the stellar wind off the hot O-type star BD+60°2522. The shell is about eight light years across, and is located about 8500 light years away. Modified Hubble palette image, with SII mapped to red, Ha to green and OIII to blue.



Exposure: Total exposure time about 24.7 hours, 37:16:21 x 20mins SII:Ha:OIII. All bin 1x1. Captured between August and October 2018.
Light pollution: Bortle 8 (white zone, NELM about 4.5)
Seeing: Subs were 1.8-2.2 arcsecs FWHM
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: Same

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 5nm Ha/SII, 3nm OIII, Type IIe LRGB
Rotator: Optec Pyxis 2", connected via Andy Galasso's 0.4 driver (Optec Pyxis Rotator AG)
Focuser: Rigel Systems GCUSB_nStep with driver version 6.0.7
OAG: Orion Thin OAG
Guide cam: Lodestar (first generation). 4 second exposures
Automation SW: Sequence Generator Pro 3.0.0.4 beta
Guide SW: PHD2.6.3, connected to guide cam via native SXV driver
ASCOM: ASCOM 6.3.0.2831
Platesolving: PlateSolve 2, failover to local Astrometry.net 0.19 server
Collimation: Metaguide 3, using ASI120MM connected via ZWO Direct Show driver 3.0.0.2

Processing Workflow by Workspace in PixInsight 1.85

1. Calibration
BatchPreProcessing with flats, darks and bias, using Cosmetic Correction with master dark

2. Stack and Mure Denoise
Blink to preview and reject a few frames
Mure Denoise

3. Linear Processing
Dynamic Crop
Dynamic Background Extraction
Deconvolution with Dynamic PSF and star mask as deringing support

4. Stretching
Histo Trans, two iterations
Curves Trans
Noise Reduction with TGV Denoise and Multiscale Median Transform (following David Ault’s Astro Imaging Channel tutorial).

5. Color Combination and Processing
Combined channels with PixelMath to create color image
Curves to boost color saturation
Reduce magenta halos:
Invert image to change magenta to green
SCNR to shift halos to yellow
Reinvert
SCNR to shift green to yellow

6. Final
Copy image and stretch with Curves to bring out surrounding nebulosity
In Photoshop:
Layer stretched image on top of original
Apply radial gradient mask such that original is used for core and stretched image is used for outer nebulosity
Save for Web as JPG