Focal Pointe Observatory
Astrophotography by Bob Franke

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M15 - Globular Cluster

 

Click the image for a higher resolution view. (2619 x 1746 - 1.11 MB)

Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at 0.85 and 2.98 arcsec/pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ FW8 filter wheel, AstroDon Gen-2 Filters

Acquisition Data

10/1/2014 to 10/27/2014 Chino Valley, AZ... with CCD Commander & CCDSoft, AOL guided.

Exposure

RGB

405 min. (9 x 15 min. each)   Bin 1x1

Software & Processing Notes

  • CCDSoft, CCDStack, PixInsight and Photoshop CS6.

  • eXcalibrator v4.25 for (g:r) color balancing, using 92 stars from the SDSS-DR9 database.

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

  • CCDStack to calibrate, register, normalize, data reject, combine the sub exposures and create the RGB image.

  • PixInsight processing includes gradient removal with DynamicBackgroundExtraction and the initial non-linear stretching with HistogramTransformation & MaskedStretch.

  • PhotoShop for the final touch-up.

  • Noiseware 5, a PhotoShop plug-in.

Comment

The cluster is shown rotated 90 counter clockwise.
 

M15 (NGC 7078) is a globular cluster in the constellation Pegasus, at a distance of about 33,600 light years. Jean-Dominique Maraldi discovered the cluster in 1746. The estimated age is about 12 billion years, making it one of the oldest known globular clusters.

M15 is about 175 light years in diameter and contains over 100,000 stars. Data from the Hubble Space Telescope suggest that an intermediate-mass black hole resides at the center.