One would think there is gravitational lensing around 4874, but no - I can't summarise it any better than NASA/ESA:
"In the centre of a rich cluster of galaxies located in the direction of the constellation of Coma Berenices, lies a galaxy surrounded by a swarm of star clusters. NGC 4874 is a giant elliptical galaxy, about ten times larger than the Milky Way, at the centre of the Coma Galaxy Cluster. With its strong gravitational pull, it is able to hold onto more than 30 000 globular clusters of stars, more than any other galaxy that we know of, and even has a few dwarf galaxies in its grasp.
...
Recently, astronomers discovered that a few of these point-like objects are not star clusters but ultra-compact dwarf galaxies, also under the gravitational influence of NGC 4874. Being only about 200 light-years across and mostly made up of old stars, these galaxies resemble brighter and larger versions of globular clusters. They are thought to be the cores of small elliptical galaxies that, due to the violent interactions with other galaxies in the cluster, lost their gas and surrounding stars." (
Credit: ESA/Hubble & NASA,
https://esahubble.org/images/potw1138a/, accessed 02.04.2023)
This also explains why I quit gathering Ha data after around 2 hours, as there is little to gain. Hence stuck to LRGB.
Robert
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