Instrument

Takahashi FSQ-106ED @ f/5.0 (530 mm F.L.) Captured at 2.1 arcsec/pixel.  Shown at 3.73 and 7.96 arcsec/pixel.

Mount

Paramount MyT

Camera

SBIG STF-8300M Self Guiding Package w/ mono ST-i, using AstroDon E-Series RGB filters.

Acquisition Data

8/7/2016 to 8/13//2016  Chino Valley, AZ with CCD Commander & CCDSoft. 

Exposure

 RGB ratios are 1.00, 1.18, 1.16

Software

• CCDSoft, PixInsight & Photoshop CS6.

• eXcalibrator v5.0 for (g:r) color balancing, using 275 stars from the APASS database.

• PixInsight processing includes calibration, registering, stacking, RGB creation, gradient removal, non-linear stretching with HistogramTransformation and the background stars were dimmed with MorphologicalTransformation.

• PhotoShop for the final touch up.

Comment

North is to the top.

IC 4756 is an open cluster in the Serpens constellation, at a distance of about 1500 light years from Earth. Solon I. Bailey discovered the cluster very early in the twentieth century. Later, Kasimir Graff independently discovered it in 1922.

With its apparent extended size, the cluster is difficult to detach from the relatively dense population of background stars. This accounts for IC 4756's somewhat late discovery. In the above image, the background stars were slightly dimmed to make the cluster more visible. This technique is most often used to increase the visibility of faint nebulae.