Celestial hemisphere:  Northern  ·  Constellation: Pegasus (Peg)  ·  Contains:  NGC 7317  ·  NGC 7318  ·  NGC 7319  ·  NGC 7320  ·  NGC 7331  ·  NGC 7333  ·  NGC 7335  ·  NGC 7336  ·  NGC 7337  ·  NGC 7338  ·  NGC 7340  ·  Stephan's Quintet
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Deer Lick Group and Stephan's Quintet, Ben Koltenbah
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Deer Lick Group and Stephan's Quintet

Getting plate-solving status, please wait...
Deer Lick Group and Stephan's Quintet, Ben Koltenbah
Powered byPixInsight

Deer Lick Group and Stephan's Quintet

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Description

This is an image comprised of the Deer Lick Group (upper left) and Stephan's Quintet (lower right) in Pegasus.

According to Wikipedia and the Concise Catalog of Deep-Sky Objects, the Deer Lick Group contains the larger unbarred spiral galaxy NGC 7331 (Caldwell 30) and members NGC 7335, 7336 (lenticular or unbarred spirals), 7337 (barred spiral), 7340 (elliptical). The latter are often referred to as the "fleas". NGC 7331 is about 40 Mly distant, and its "companions" about 332, 365, 348, 294 Mly distant, respectively. Its apparent size is about 10.2' x 4.2' with magnitude 9.8. NGC 7331 is often called the Milky Way's twin as it is similar in size and structure, although the Milky Way is more recently thought to be a barred spiral. NGC 7331 is notable for having a retrograde rotating bulge.

Edouard Stephan discovered the quintet of galaxies in 1877. Four of the galaxies form the first compact galaxy group ever discovered, called the Hickson Compact Group 92. These will likely merge with one another in the future. There is a filament that lies in the regions between the galaxies, most visible in green (although not visible in this image), that results from a shock wave formed by one of the galaxies falling into the center of the group. The three larger galaxies are NGC7319 (upper), NGC 7318A (adjacent, lower right), NGC 7320 (adjacent, lower left). NGC 7317 is to the lower right from this group of three. NGC 7320C is to the upper left of the main three. They vary in magnitude from 13.9 to 16.7. These are roughly 300 Mly distant, although I was unable to find more precise values than that.

I used PixInsight to create the image, including the new PhotometricColorCalibration process. I used the Average Spiral Galaxy calibration option. The result seems, at least to me, to overemphasize the blue stars. I had hoped to bring out more blue in the spiral arms of NGC 7331, but this is the result of the calibration mentioned. The imaging scope was an ES127, FL 952mm. The imaging camera a QSI 683 wsg-8 with pixel size 5.4 micron. The final image has a resolution of 1.166 "/px. I wish to return to image each group separately at higher resolution in the future.

Revision D was my attempt to fix many problems and mistakes with the original. I used PI's PhotometricColorCalibration with option G2V to balance the RGB channels. Following this I extracted the channels again and applied MorphologicalTransformation on B to suppress the large bloated stars in B. Following recombination I then proceeded normally with noise reduction, stretching, HDRMultiscaleTransformation, stretching, CurvesTransformation and then channel extraction of Lab. The a and b channels were used to combine with the synthetic L channel. I also applied a mild SCNR to remove green background, trying not to overdue this as I did before.

The sythentic L channel was also treated with MorphologicalTransformation to reduce the bloated stars followed by Deconvolution, noise reduction, stretching, HDRMultiscaleTransform, CurvesTransformation. The LRGB combination required only mild CurvesTransformation and stretching.

I find the new revision to be an improvement in reducing star bloat and better balancing the colors. The star reduction was not perfect as I can see darker circles around the brighter stars. These could be hidden better with more of a black stretch, but I thought I'd leave it as is for now. MorphologicalTransform has a dark level setting that is quite subtle and difficult to match exactly with the background level.

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Revisions

  • Deer Lick Group and Stephan's Quintet, Ben Koltenbah
    Original
  • Deer Lick Group and Stephan's Quintet, Ben Koltenbah
    B
  • Deer Lick Group and Stephan's Quintet, Ben Koltenbah
    C
  • Deer Lick Group and Stephan's Quintet, Ben Koltenbah
    D
  • Final
    Deer Lick Group and Stephan's Quintet, Ben Koltenbah
    E

B

Description: Synthetic Luminance Channel

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C

Description: Annotated Image

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D

Description: New LRGB Version with B Channel Morphological Transformation

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E

Description: LRGB Revision Using PCC Option Photon Equalization, No MorphologicalTransformation

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Deer Lick Group and Stephan's Quintet, Ben Koltenbah

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