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Astrophotography by Bob Franke

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NGC 6811

 

Click the image for a 60% size wide field view. (2400 x 1600 - 1.45 MB)

Instrument

12.5" RCOS @ ~ f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at  1.06 and 2.64 arcsec/pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ FW8 filter wheel & AstroDon Gen-2 RGB filters.

Acquisition Data

8/7/2017 to 8/17/2017 Chino Valley, AZ. with CCD Commander & CCDSoft.  AOL guided

Exposure

RGB

 360 min (12 x 10 min. each) Bin 1x1

Software & Processing Notes

 

  • CCDSoft, CCDStack, PixInsight, Photoshop CS6.

  • eXcalibrator v6.2 for (g:r),(b:r) color balancing, using 1185 stars from the Pan-STARRS database.

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

  • CCDStack to calibrate all sub exposures.

  • PixInsight processing includes CosmeticCorrection, data  rejection, mean combine all the sub-exposures, create the RGB image, gradient removal and non-linear stretching with HistogramTransformation.

  • PhotoShop for additional background neutralization and background smoothing.

  • Noiseware 5, a PhotoShop plug-in.

Comment

 

The cluster is shown rotated 130 clockwise.

John Herschel discovered NGC 6811 in 1829. The cluster is in the constellation of Cygnus, at a distance of 3000 to 3900 light-years. The presence of white hot stars suggests an intermediate age of approximately 700 million years. This is relatively young as compared to the Sun's middle age of about 4.5 billion years.

In 2013, astronomers found two exoplanets in the cluster. The group measured the age of NGC 6811 to be one billion years, slightly older than previous estimates.