Link to annotated image
M 64 is a relatively isolated spiral galaxy 17 million light-years away. It was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier the next year. Its morphological classification in the De Vaucouleurs system is (R)SA(rs)ab, where the '(R)' indicates an outer ring-like structure, 'SA' denotes a non-barred spiral, '(rs)' means a transitional inner ring/spiral structure, and 'ab' indicates that the spiral arms are fairly tightly wound.
The interstellar medium of Messier 64 consists of two counter-rotating disks that are approximately equal in mass, but the stars themselves show no signs of counter-rotation. Possible formation scenarios include a merger with a gas-rich satellite galaxy in a retrograde orbit, or the continued accretion of gas clouds from the intergalactic medium. It has a diameter of 54,000 light years.
M64 is a type 2 Seyfert galaxy with an HII/LINER nucleus. The central region is a weak source of radio emission. A soft X-ray source has been detected at the nucleus, which is most likely coming from the circumnuclear region rather than directly from an active galactic nucleus.
The annotated image shows little but the ordinary range of background galaxies and quasars. Three galaxy clusters (one of which is probably a duplicate) are charted, but close examination of a heavily stretched image reveals nothing but the ordinary distribution of background galaxies.
Exposure: Total exposure time 20.25 hours, 468:47:47:45 x 2 minutes LRGB. All bin 1x1. Data collected in March and April of 2021.
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 arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 0.88 arcsecs/pixel (67% 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: 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 Software: Pixinisight, Affinity Photo, Photoshop CS2
Processing Workflow by Workspace in PixInsight 1.8.8:
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 and registration with WBPP
2. Stack and Mure Denoise
Image Integration on each channel
Mure Denoise on each channel
RGB Combination for RGB frames
Dynamic Crop
Dynamic Background Extraction
3. Luminance Linear Processing
Deconvolution to Sharpen:
Dynamic PSF to create PSF image
Deconvolution, using a mask created in Affinity Photo to sharpen selected areas only
4. Luminance Stretching
Histo Trans x 3
Curves Trans
TGV Denoise
Aggressive Multiscale Median Transform (with an inverted luminance mask) to remove background lumpiness
5. RGB Linear Processing
Photometric Color Calibration, using Elliptical [sic] Galaxy white reference. I found that using Average Spiral Galaxy as the white reference left the entire galaxy too yellow/orange.
6. RGB Stretching
Histo Trans x 2
Boost color saturation with Curves
Histo Trans
Curves Trans
7. Color Combination
LRGB Combination of Luminance and RGB images
Curves Trans, using a range mask of the galaxy, to boost blue color in the arms
8. Background Subtraction
a. Create an image of the background:
1. StarNet++ to create a starless image
2. Modify the starless image in Affinity Photo and Photoshop:
a. Use the Healing Brush and CloneStamp tools to remove halos, leaving only the background
b. Select the galaxy with the Magic Wand tool and expand the selection so that the whole galaxy is selected. Then delete it, and use the Smudge tool to “push in” color and patterns from the edges into the hole left by the galaxy. Then blur that area with Gaussian Blur to avoid sharp transitions.
c. Apply a heavy Noise Reduction filter so that noise is not removed during the subtraction process.
b. Subtract the background image from the original image (using Image>Apply Image) to remove remaining messy clumps in the background (and apply an offset so that the background is pure black)
c. Layer Galaxy, Background Galaxies and Dust Lane Images together with masks, save as TIFF and move back into PI
9. Final Adjustments
Histo Trans to darken background
No star halo reduction on this image
10. Final
Final Histogram Transformation
ICC Profile Transform to sRGB
Resample at 75% scale
Save as JPG
ImageSolve
ImageAnnotation (using custom catalogs for UGC/PGC galaxies, clusters and quasars)
