Link to redshift chart
In addition to the five magnitude 14-15 galaxies of Hickson 58, this 22 x 27 arcminute FOV contains two Abell clusters, and a 1.5 degree FOV would capture five more. In March 2013 Owen Brazell wrote on the Webb Society Galaxy of the Month page that he was surprised this FOV hadn’t attracted any amateur images, and that situation doesn’t seem to have changed until now. I found nothing except the survey images and an EAA screen grab.
Interesting Features: Note the curious jet emanating southward from NGC 3819. Although this jet is clearly shown in the SDSS image, I haven’t found any explanation for it, or even any comment about it. As for the background galaxies, to my eye the most interesting is mag 18.5 SDSS J114246.46+101800.2, which is the tiny blue curlicue just right of LEDA (PGC) 1377346 near top center, but other than a note that it’s also a UV source I can’t find anything about it. NGC 3822 and 3817, as well as LEDA 139662 and 1379719 in Abell 1356, are cataloged as Seyfert galaxies, meaning that they have very bright nuclei thought to be powered by supermassive black holes. Note that NGC 3822 appears to have been double-entered in the NGC as 3848.
Galaxy Clusters Galore: There are so many galaxy clusters charted in this region that I didn’t try to include all of them in the annotated image. Abell 1354, which seems to be cross-cataloged as Zwicky 4428, is the clump at upper left, and Abell 1356, which has Zwicky 4429 plotted in roughly the same position, is the looser grouping on the right, dominated by LEDA (PGC) 139664. The other galaxy catalogs plot at least 16 more clusters in this image, some with over 50 members. I can’t tell which of these are supposed to be cross-references to the Abell/Zwicky clusters, subgroups of those, or entirely different clusters.
But in theory there are three main clusters in this image. Based on redshifts, Hickson 58 lies about 290 million light years away, and is spread out across 15 million light years. Beyond that are Abell 1356 (right) at 950 mly and Abell 1354 (left) at 1.4 gly. But the redshift chart shows a more subtle story. There are concentrations of galaxies with redshifts around 0.02, 0.07, 0.11 and 0.15. 0.02 is the five-galaxy Hickson 58 and a host of small companions. 0.07 and 0.11 are the two Abell clusters, but they’re both spread across the whole field rather than being separated into the more obvious clumps at right and left. And the concentration at 0.15, which is also spread out across the whole FOV, appears to be a separate cluster, since it’s 500 mly beyond Abell 1354. And a deep redshift survey, probably part of SDSS Data Release 13, is now in the NASA Extragalactic Database. That plots a host of mag 21-22 specks, most of them visible in this image, scattered across most of the FOV, with redshifts indicating distances up to 10 billion light years.
Silly but Useful Mistake: I put Hickson 58 on my list while looking for new galaxy cluster targets after completing the NGC 3825 galaxy group in January. When I first started processing Hickson 58, I thought the field looked somehow familiar, and that’s because Hickson 58 . . . IS the NGC 3825 galaxy group. I was so focused on the idea of a Hickson group and two Abell clusters in the same FOV that I never realized that it was the same galaxy group, just rotated 90 degrees to get the two Abell clusters. On the upside, I have a LOT of data on this target!
Exposure: Total exposure time 32.8 hours, 760:73:73:78 x 2 minutes LRGB, all bin 1 x1.. Captured January and April-May 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 2.4 arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 0.9 arcsecs/pixel (2/3 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 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 3.1.0.457
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 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 at variance scale 0.75 on each channel
RGB Combination for RGB frames
Dynamic Crop
Dynamic Background Extraction
3. Luminance Linear Processing
Deconvolution or Multiscale Linear Transform to Sharpen:
Dynamic PSF to create PSF image
Deconvolution, using a luminance mask and a star support image to avoid ringing on stars
4. Luminance Stretching
Histo Trans x 2
Curves Trans
TGV Denoise
Aggressive Multiscale Median Transform, using an inverted luminance mask, to remove lumpiness in background
5. RGB Linear Processing
Photometric Color Calibration, using Average Spiral Galaxy white reference
6. RGB Stretching
Histo Trans
Boost color saturation with Curves
Curves Trans
TGV Denoise
Aggressive Multiscale Median Transform, using an inverted luminance mask, to remove lumpiness in background
7. Color Combination
LRGB Combination of luminance and RGB images to create “Galaxy” image
8. Background Subtraction
a. Create an image of the background (an artificial flat):
1. StarNet++ to create a starless image
2. Modify the starless image in 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 Galaxy 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. Save as TIFF and move back into PI
9. Star Reduction
I used a modified version of Adam Block’s star reduction technique:
StarNet to create a new “Starless Image”
Extract two copies of luminance from the Galaxy Image, then apply a 7-layer MLT, unchecking the residual layer, to one to create a rough star mask.
Binarize to select only the stars
MorphTrans using erosion to eliminate the smallest stars
MorphTrans using dilation to enlarge the remaining stars
Edit the mask with CloneStamp to exclude any background galaxies
Convolution to blur star edges
Pixel Math: subtract luminance image from blurred star mask so that cores are excluded from mask, and on ly halos are represented in the mask = “Halo Mask”
Apply Halo Mask to Galaxy image, then run PixelMath to use Starless Image where halos otherwise would be
10. Final
Final Curves Trans to darken background
ICC Profile Transform to sRGB
Resample to 67% of scale
Save as JPG
ImageSolve
ImageAnnotation (using custom catalogs for UGC/LEDA galaxies, clusters and quasars)
