Abell 3537 is a large, spread out cluster of at least 35 galaxies in Centaurus. The brightest member is ESO 443-22 (a blazar), located just above and to the left of center. The galaxies in the count are an average magnitude of 13.9.
Abell 3531 is a smaller grouping of at least 36 galaxies with an average magnitude of 16.7. This group is located at the bottom right. See the annotated image.
Luminance – 12x600s – 120 minutes – binned 1x1
RGB – 8x300s – 40 minutes each – binned 2x2
240 minutes total exposure – 4 hours
Imaged on January 14th, 16th and 17th, 2021 from Dark Sky New Mexico at Rancho Hidalgo (Animas, New Mexico) with a SBIG ST-8300M on an Astro-Tech AT90EDT at f/6.7 603mm.
LRGB - https://www.flickr.com/photos/dcrowson/51900674395/sizes/l/
LRGB annotated - https://www.flickr.com/photos/dcrowson/51900114143/sizes/l/