Located in the direction of Serpens close to the star, 5 Ser, in the sky it is 24,500 ly distant and approximately 160 ly across. Mass is about 8.6x105 solar masses. It contains over 100 variable stars, mainly RR Lyrae stars - important standard candles for determining distance - and two milli-second pulsars (ie, neutron stars, one of which is in a binary) which has been studied to gain insights into the nature of neutron degenerate matter. The cluster has also been used to study other aspects of astrophysical interest.

Classified, V (intermediate concentrations), on the Shapley-Sawyer globular cluster concentration scale (1927). 


Camera: SBIG STL11000M, Astrodon filters Scope: Takahashi TOA-130, f=1000mm, f7.7, fov 1.0 x 0.7
Mount: Takahashi EM-200 Temma 2 Guiding: internal
Filters/Exposures: R:G:B = 10:10:1030m Location: ASV's LMDSS, Lady's Pass, Victoria, Australia
Date: August 2023 Processing: CCDStack2, RegiStar and Photoshop CS5