Instrument

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

Mount

Paramount ME

Camera

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

Acquisition Data

8/6/2020 to 8/11/2020 Chino Valley, AZ. with CCD Commander & TheSkyX.  AOL guided

Exposure

Software & Processing Notes

• CCDStack, PixInsight, Photoshop CS6.

• eXcalibrator v6.2 for (g:r),(b:r) color balancing, using 704 stars from the Pan-STARRS database.

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

• CCDStack to calibrate and normalize the sub exposures and moderate sharpening with Positive Constraint Deconvolution.

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

• PhotoShop for additional background neutralization.

• Noiseware 5, a PhotoShop plug-in for background smoothing.

Comment

The cluster is shown rotated 80° clockwise.

NGC 6749 is a faint globular cluster, at a distance of about 25,000 light years, in the constellation Aquila. The cluster is a very loosely packed with a surface brightness of only magnitude 21.8 and is located in a rich star field. These three conditions combine to make NGC 6749 the most difficult globular cluster to observe visually. Surprisingly, this was the first globular discovered by John Herschel.

The cluster has a galactic latitude of only -2.2°. So, we view it through much dust and nebulae. This scatters the blue light, making the cluster appear red, like the Sun at sunset.