This star cluster is one of the oldest open clusters in our sky, perhaps 8 billion years old, and lies around 13,300 light years away. Estimates gives it a mass equal to 10,000 suns, and educated guesses suggest that at formation its mass was 10x greater. A color-magnitude diagram included in the study linked below suggests that the cluster's stars are magnitude 14 and dimmer. My image captures stars down to around mag. 19, but the cluster contains thousands more stars dimmer than that.
See https://iopscience.iop.org/article/10.3847/1538-4357/aae4e5/pdf.
The red star to the upper right of the cluster is U Lyrae, a carbon star.
This image is 15x1200" with the 203mm Synta ONTC Newtonian at f/4.95, Atik 460 EXC, and Astronomik CLS filter.
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