Imaged M13, the Hercules globular cluster, on the night of July 21, 2023. M13 has an apparent magnitude (v) of 5.8 and an apparent size of ~20 arcmin.
Per NASA (reference:
https://www.nasa.gov/feature/goddard/2017/messier-13-the-hercules-cluster): "Like shiny flakes sparkling in a snow globe, over 100,000 stars whirl within the globular cluster M13, one of the brightest star clusters visible from the Northern Hemisphere. Located 25,000 light-years from Earth with an apparent magnitude of 5.8, this glittering metropolis of stars in the constellation Hercules can be spotted with a pair of binoculars most easily in July."
Imaged with a William Optics GT81 at F4.7 (382 mm focal length) using Flat6A II field flattener/0.8x reducer, UVIRcut filter, and ZWO ASI 533MC Pro. Total integration time of 2.5 hours: 71 subs at Gain = 100 with an exposure time of 120 sec.
Pre-processed using Pixinsight's weighted batch pre-processing script (WBPP) to perform calibration, debayering, registration, local normalization, and integration. Background removed using GradXpert. Initial post-processing in Pixinsight: spectrophotometric color calibration, blur x terminator, and noise x terminator. STF stretch, HDR transformation using EasyHDR script, local histogram transformation, and color saturation adjustment.
Original version: M13 OSC RGB image
Rev B: M13 OSC RGB image, inverted
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