Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at 1.12 and 2.84 arcsec/pixel.

Mount

Paramount ME

Camera

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

Acquisition Data

9/25/2015 to 10/1/2015 Chino Valley, AZ... with CCD Commander & CCDSoft, AOL guided.

Exposure

RGB ratios are 1.00, 0.96 & 1.06

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.

Comment

The cluster is shown rotated 150° clockwise.

M103, or NGC 581, is an open cluster in the constellation Cassiopeia. It was discovered by Charles Messier in 1781. At about 9000 light years, it is one of the most distant known open clusters.