Galaxy Cluster Abell 262 in Andromeda

Abell 262 is located on the Andromeda-Triangulum border, about 240 million light years away. Its largest member is the huge cD elliptical NGC 708, but it contains an unusually high proportion of spiral galaxies. All of the brighter galaxies in this image are part of the cluster. NGC 710, the bright blue spiral below center, has a Tully-Fisher measurement of only 114 million light years, which would make it a foreground galaxy in the middle of the Taurus Void. However, its redshift measurements correspond to a distance of about 280 million light years, so it seems more likely to be a cluster member.

Abell 262 is part of the Perseus-Pisces supercluster, a huge string of galaxy clusters spanning 40 degrees of the sky. I found no range estimates for any of the background galaxies. The bright galaxies at the core of Abell 262 are frequently called the Fath cluster, after astronomer Edward Arthur Fath (1880-1959), who laid some of the groundwork leading to the conclusion that "spiral nebulae" are separate galaxies rather than part of our Milky Way, but no one seems to know how his name came to be associated with this cluster.


Exposure: Total exposure time about 12.8 hours, 263:38:44:41 x 2 minutes LRGB. All bin 1x1. Data collected November 2019 to January 2020.
Light pollution: Bortle 7-8 (white zone, NELM about 4.5)
Seeing: Average FWHM of subs around 2.4 arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 1.2 arcsecs/pixel (50% of 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 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 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 3.0.0.8
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 1.86

1. Calibration
BatchPreProcessing with flats and bias, using Cosmetic Correction with master dark
Blink to preview and reject a few frames
Subframe Selector for luminance to confirm selections and weight by FWHM and SNR
StarAlign to register frames

2. Stack and Mure Denoise
Image Integration on each channel
Mure Denoise on each channel
RGB Combination for RGB frames
Dynamic Crop

3. Luminance Linear Processing
Dynamic Background Extraction
Deconvolution on luminance frame, using a mask created manually in Photoshop so that only the galaxies I wanted were sharpened.

4. Luminance Stretching
Histo Trans, Curves Trans
TGV Denoise
Aggressive Multiscale Median Transform to remove lumpiness in background, using an inverted and blurred luminance frame as a mask to protect highlights

5. RGB Linear Processing
Dynamic Background Extraction
Photometric Color Calibration

6. RGB Stretching
Histo Trans
Masked Stretch
Curves

7. Color Combination
LRGB Combination of luminance and RGB images

8. Star Reduction and Background Removal
Star masks for large stars
Morphological Transform to erode stars
Photoshop: Create an artificial flat by eliminating the remaining small stars with the Dust and Scratches filter
Subtract the artificial flat from the main image, masking out the galaxies
Use Radial Blur filter to obscure comatic blue halos on bright stars

9. Final
Final Histogram Transformation
ICC Profile Transform to sRGB
Resample to 50% of scale
Save as JPG