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Astrophotography by Bob Franke

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M14 - Globular Cluster

 

Click the image for a 73% size view. (2100 x 1400 - 1.12 MB)

Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at 0.87 and 2.45 arcsec/pixel.

Mount

Paramount ME

Camera

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

Acquisition Data

7/24/2015 to 8/5/2015 Chino Valley, AZ... with CCD Commander & CCDSoft, AOL guided.

Exposure

RGB

495 min. (11 x 15 min. each channel) Bin 1x1

RGB ratios are 1.00, 0.97 & 1.08

Software & Processing Notes

  • CCDSoft, CCDStack, PixInsight, Photoshop CS6.

  • No SDSS stars were available for color balancing, so a standard image-train color calibration was used, as determined by eXcalibrator v4.25, and then adjusted for altitude extinction.

  • 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 and the non-linear stretching with HistogramTransformation.

  • PhotoShop for the final touch-up.

  • Noiseware 5, a PhotoShop plug-in.

Comment

The cluster is shown rotated 165 clockwise.

M14, or NGC 6402, is a globular cluster in the constellation Ophiuchus at a distance of about 30,000 light-years. It was discovered by Charles Messier in 1764.

M14 is a wonderful example of how galactic extinction effects color. The cluster has a galactic latitude of only 14.8. This means we view it through much dust and nebulae. This causes the color to shift towards the red, just like the Sun at sunset.