M23 (NGC 6494 and others) is a trumpler (https://en.wikipedia.org/wiki/Trumpler_classification) class I 2 r open cluster located approximately 2150 light-years away in Sagittarius.
I also caught asteroid 74 Galatea while capturing the luminance. The trail can be found under a star on the left side of the image just below center.
Luminance – 12x600s – 120 minutes – binned 1x1
RGB – 8x300s – 40 minutes each – binned 2x2
240 minutes total exposure – 4 hours
Imaged September 26th and 27th, 2019 at Dark Sky New Mexico at Rancho Hidalgo (Animas, New Mexico) with a SBIG ST-8300M on an Astro-Tech AT90DT at f/6.7 603mm.
LRGB - https://www.flickr.com/photos/dcrowson/48838474107/sizes/l/