M13 | Great Hercules Cluster

Several hundred thousand stars packed into a ball about 145 light-years across, and at roughly 12 billion years old it’s nearly as old as the universe itself. In 1974 the Arecibo message — humanity’s first deliberate radio broadcast to extraterrestrials — was aimed at this cluster. The small galaxy NGC 6207 photobombs the frame from tens of millions of light-years beyond.

Captured 2026-04-18 at Eliot ME — 655 frames, 1.8 hours. Siril 1.4.4 + GraXpert 3 + RC-Astro BXT/NXT: single-session stack, GraXpert background extraction, SPCC color calibration, BXT star sharpening, linked stretch, star-preserving NXT, floor desaturation.