NGC 6522 (VDBH 256 and others), the cluster on the right, is a Shapley-Sawyer class VI (http://en.wikipedia.org/wiki/Shapley%E2%80%93Sawyer_Concentration_Class) globular cluster located approximately 26,100 light-years away in Sagittarius. A 2008 paper (https://arxiv.org/pdf/0908.3603.pdf) suggests that it could be the oldest (> 12 billion years) globular cluster in our Milky Way.
NGC 6528 (ESO 456-48, VDBH 257 and others), the cluster on the left, is a class V globular cluster located approximately 25,800 light-years away in Sagittarius.
Barnard 298 is the dark nebula located just below NGC 6528.
Luminance – 12x600s – 120 minutes – binned 1x1
RGB – 8x300s – 40 minutes each – binned 2x2
240 minutes total exposure – 4 hours
Imaged on July 13th and August 19th and 20th at the Danville Conservation Area (New Florence, Missouri) with a SBIG ST-8300M on an Astro-Tech AT90EDT at f/6.7 603mm.
LRGB - https://www.flickr.com/photos/dcrowson/50260423762/sizes/l/