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Astrophotography by Bob Franke

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Abell 1656 Galaxy Cluster

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Click the image for a ~ 70% size view. (2400 x 1600 - 1.25 MB)

Click here for a wide-field view

Instrument

12.5" RCOS @ ~ f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at  0.93 & 2.84 arcsec/pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ FW8 filter wheel & AstroDon Gen-2 Ha 6nm and LRGB filters.

Acquisition Data

4/28/2017 to 5/25/2017 Chino Valley, AZ. with CCD Commander & CCDSoft.  AOL guided

Exposure

Lum

360 min (24 x 15 min. each) Bin 1x1

RGB

405 min (9 x 15 min. each) Bin 2x2

eXcalibrator RGB ratios are 1.00, 1.05 & 1.19

Software & Processing Notes

 

  • CCDSoft, CCDStack, PixInsight, Photoshop CS6.

  • eXcalibrator v5.1 for (g:r),(b:r) color balancing, using 30 stars from the SDSS-DR9 database.

  • CCDBand-Aid to repair KAI-11000M vertical bars.

  • CCDStack to calibrate all sub exposures data.

  • PixInsight... CosmeticCorrection to cleanup the remaining hot and cold pixels, to register, data  reject, mean combine, create the LRGB image, gradient removal, non-linear stretching with HistogramTransformation .

  • PhotoShop for additional background neutralization and background smoothing.

  • Noiseware 5, a PhotoShop plug-in.

Comment

 

Shown rotated 32 counterclockwise.

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. This image only shows the central region which is dominated by two giant elliptical galaxies... NGC 4874 and 4889.