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Astrophotography by Bob Franke

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Abell 1656 Galaxy Cluster


Click the image for a 1.38 arcsec/pixel  display (1800 x 1200)


12.5" RCOS @  ~f/9 (2880 mm fl) 1.28 arcsec / pixel.  Shown resampled to 2.21 arcsec / pixel.


Paramount ME


SBIG STL-11000 w/ internal filter wheel, AstroDon Filters

Acquisition Data

3/15/2009 to 3/24/2009  Chino Valley, AZ


Lum    400 min (40 x 10 min, bin 2x2)

RGB    360 min (12 x 10 min each, bin 2x2)


  • CCDSoft, CCDStack, PixInsight & Photoshop CS6.

  • eXcalibrator v4.25 for (g:r) color balancing, using 24 stars from the SDSS-DR9 database.

  • CCDStack to calibrate, register and stack the sub exposures and create the RGB image.

  • PixInsight processing includes gradient repair, non-linear stretching with HistogramTransformation and selective use of HDRMultiscaleTransform to enhance the detail individual galaxies.

  • PhotoShop for combining the images with varying galaxy detail, creating the LRGB and final touch up.


North is ~ to the top, the image is rotated 25 deg's CCW

The Coma Cluster (Abell 1656) is a large cluster of galaxies that contains over 1,000 identified galaxies. Abell 1656 and the Leo Cluster (Abell 1367) are the major components of the Coma Supercluster. At a distance of 320 million light years, the apparent extent of the cluster is three times larger than the Moon, half of which is shown in this image. The central region is dominated by two giant elliptical galaxies... NGC 4874 and 4889.

Notable Object:
QSO [HB89] 1256+280  With a red shift of 2.66, this quasar is at a distance of about 10.3 to 12.3 Billion Light Years, depending on who's redshift calculator you use.