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Contains:  NGC 6166
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ACO 2199: Brilliant Galaxy Cluster, 


            Robert Churan
ACO 2199: Brilliant Galaxy Cluster

ACO 2199: Brilliant Galaxy Cluster

Technical card

Resolution: 5100x3450

ZWO Blue 1.25": 30x512"
ZWO Green 1.25": 30x512"
ZWO Luminance 1.25": 88x512"
ZWO Red 1.25": 30x512"

Integration: 25.3 hours

Darks: ~50

Flats: ~50

Bias: ~50 job: 2777519

RA center: 247.161 degrees

DEC center: 39.552 degrees

Pixel scale: 0.380 arcsec/pixel

Orientation: 1.190 degrees

Field radius: 0.325 degrees

Data source: Backyard


An Abell galaxy cluster of Richness Class II and Bautz-Morgan type I located around 417 million light years away in the constellation of Hercules. The cluster contains at least 290 identifiable galaxies. It is the very definition of Bautz-Morgan type 1 due to the central dominant galaxy NGC 6166 at its center.

NGC 6166 is the primary galaxy in the cluster located 490 million light years away from us. It is a supergiant elliptical galaxy with a supermassive black hole of around 30 billion M☉, and is actually one of the strongest known galaxies in terms of X-ray emissions. This galaxy is suspected to have formed through collisions due to the many globular clusters within. A 2016 study estimated 39,000. The galaxy also has four apparent core regions, shown in the lower left of the annotated image. There is the large main core, A, and three others. B and D appear to themselves be merging. This galaxy has an active core that produces emissions strong enough to have classed this galaxy a quasar.

Three other objects have been annotated. Two are quasars 9.4 and 10.6 billion light years away. The third is identified as a galaxy 5.3 billion light years away, though to appear so blue at 5.3 billion light years it must be an ultraviolet emission source (UvES).

This cluster has been all my work over the past month. Despite clouds and the appearance of the moon interrupting me, I pushed on to grab all 25 hours of data. I was amazed when first looking at databases to see what objects I found once I first noticed the QSO more than 10 billion light years from us appearing in my image. It took me several minutes to regain my composure and then several hours of intense pondering. That's possibly my favorite thing about these galaxy clusters. They sure aren't the prettiest objects out there, yet each tells an amazing story and will leave you pondering things about the nature of this vast and awesome universe we find ourselves in for hours on end.

Clear skies to all,



Robert Churan
License: None (All rights reserved)


  • Final
    ACO 2199: Brilliant Galaxy Cluster, 


            Robert Churan
  • ACO 2199: Brilliant Galaxy Cluster, 


            Robert Churan


Annotated with QSOs, a UvES, and a zoom of the core of 6166

Sky plot

Sky plot


ACO 2199: Brilliant Galaxy Cluster, 


            Robert Churan