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Contains:  NGC 7320, NGC 7319, NGC 7318, Stephan's Quintet, NGC 7317
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Stephan's Quintet, 


            Joel Shepherd
Stephan's Quintet

Stephan's Quintet

Technical card

Resolution: 1280x953

Dates:Aug. 15, 2017Aug. 21, 2017Aug. 25, 2017

Baader Planetarium B 1.25": 30x300" bin 1x1
Baader Planetarium G 1.25": 30x300" bin 1x1
Baader Planetarium R 1.25": 30x300" bin 1x1

Integration: 7.5 hours

Avg. Moon age: 18.57 days

Avg. Moon phase: 20.26%

Bortle Dark-Sky Scale: 6.00 job: 2736683

RA center: 339.007 degrees

DEC center: 33.964 degrees

Pixel scale: 0.841 arcsec/pixel

Orientation: 36.205 degrees

Field radius: 0.186 degrees

Locations: Home, Seattle, WA, United States

Data source: Backyard


Subject: Stephan's Quintet: The blueish galaxy (NGC 7320) is a rather neighborly 39 million light-years away. The other galaxies are roughly 250 million light years distant and are gravitationally bound to each other. Long tendrils of stars have been stripped away from the interacting galaxies and a massive shock wave (visible via x-ray: mine, sadly, is in the shop for repair ;-) is emanating from the two colliding galaxies on the right.

Capture notes: All RGB, with a synthetic luminance. This could really stand more data: even with 90 exposures, with such a dim target there is a lot of noise in the background. A project to resume next year ...

Processing notes: I used PixInsight's new PhotometricColorCalibration for the first time on this, and the results were much better than I could get out of the usual ColorCalibration process. It was a real challenge, though, to stretch the detail out of the galaxies (especially the long star trail) without bloating the stars or pulling up the background noise. Like I said, it could probably benefit from a good stack of real luminance data.



Joel Shepherd
License: Attribution Creative Commons


  • Stephan's Quintet, 


            Joel Shepherd
  • Final
    Stephan's Quintet, 


            Joel Shepherd


Same data, reprocessed in 2019. Main differences from original processing are (A) Used MureDenoise after stacking, which is a big help with overall noise control, (B) Stretched with histogram and curves, which led to less haze around the stars at the cost of slight enlargement of the smaller stars, (C) Sharpening with PI's UnsharpMask, (D) Background smoothing with MultiscaleMedianTransform's adaptive setting. I.e. some of the tricks ... erm ... techniques I've picked up in the last year or so.

Sky plot

Sky plot


Stephan's Quintet, 


            Joel Shepherd

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Images from the EdgeHD Series