Messier 98 in Coma Berenices)

Messier 98 is an intermediate – showing both barred and non-barred characteristics – spiral galaxy located about 44 million light years away. The galaxy is a member of the Virgo Cluster. The warped shape (which to me has three dimensional aspects, almost like a corkscrew) might be due to a long-ago interaction with Messier 99, which is located about 1.3 million light years away.

The scattering of small reddish galaxies at lower right is the galaxy cluster Abell 1499, which is about 2 billion light years away. The bright galaxy in that area is NGC 4186, which is about 350 million light years away. The low surface brightness spiral at upper right is PGC 39002, located about 120 million light years away. The brighter of the two galaxies to its upper left is PGC 8989, located about 320 million light years away.i>

Exposure: Total exposure time about 12 hours, 161:62:61:55 x 2 minutes LRGB. All bin 1x1. Data collected in March 2019.
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 arsecs/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, darks 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 with Dynamic PSF and star mask for deringing support. Masked in using mask created in Photoshop.

4. Luminance Stretching
Histo Trans x 3
Curves Trans
Local Histogram Equalization on background, using mask, to enhance dust
TGV Denoise
Aggressive Multiscale Median Transform to remove lumpiness in background, using an inverted and blurred luminance frame as a mask to protect highlights
Mild Local Histogram Equalization on galaxy core

5. RGB Linear Processing
Dynamic Background Extraction
Photometric Color Calibration

6. RGB Stretching
Histo Trans x 3
Boost saturation in galaxy with Curves Trans and luminance mask

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
Plate solve image with ImageSolver
Annotate image with script
sRGB on both images
Resample to 50% of scale
Save both images as JPGs