The NGC 383 Galaxy Group

The Pisces Cloud (Arp 331) is a group of galaxies about 225 million light years away. It's near one end of the Perseus-Pisces Supercluster, a filament of galaxy clusters that stretches for 300 million light years across 40 degrees of the sky and is located on the far side of the Taurus Void from our local supercluster (Laniakea or Virgo). All of the brighter elliptical and lenticular galaxies in the image are part of the Pisces Cloud, as is the largest edge-on spiral below center. I found no distance estimates for any of the background galaxies.


Exposure: Total exposure time about 9.9 hours, 176 x 2 mins Lum, 30:54:37 x 2 mins RGB. All bin 1x1. Captured November-December 2017.
Light pollution: Bortle 7-8 (white zone, NELM about 4.5)
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 1.2 arcsecs/pixel (50% reduction)

Equipment:
Scope: C11 (standard, not Edge) with Celestron 0.63 reducer imaging at f5.7
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 IIi 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 and bias, using Cosmetic Correction with master dark

2. Stack and Mure Denoise
Blink to preview frames
Subframe Selector to weight by FWHM
Image Integration
Mure Noise Reduction on each channel. Not much improvement on Lum, significant on RGB.
Channel Combination to merge RGB channels
Dynamic Crop

3. Luminance Linear Processing
Automatic Background Extraction. Executed first for subtraction, then for division.
Dynamic Background Extraction
No Deconvolution - probably not much extra detail to get in these galaxies.

4. Luminance Stretching
Histogram Trans
Curves Trans
Noise Reduction with TGV Denoise and Multiscale Median (following David Ault’s Astro Imaging Channel tutorial).

5. RGB Linear Processing
Automatic Background Extraction
Dynamic Background Extraction
Photometric Color Calibration

6. RGB Stretching
Histo Trans and Curves Trans
Noise reduction with TGV Denoise and Multiscale Median Transform

7. Color Combine
LRGB merge
Star size reduction with star mask and MorphTrans

8. Background Removal
In Photoshop, did some coma repairs
Create background image and export it back to PI
PixelMath to subtract background from image

9. Final
Additional star size reduction with MorphTrans
Save as TIFF
Downsize 50% and save as JPG