This dense, ancient globular cluster contains countless stars bound tightly together by gravity, creating a bright, concentrated ball of light. For the astrophotographer, Caldwell 47 appears as a sparkling sphere with a bright unresolved core and delicate streamers of individual stars emerging at the edges. High-resolution telescopic images, especially those captured with long exposures and larger apertures, will reveal more structure and hint at the cluster’s granularity. Its relatively faint magnitude makes it best imaged under dark skies, with moderate to long stacking times enhancing both the cluster and the surrounding Milky Way background.
Names and Catalog numbers
- Caldwell 47
- NGC 6934
- Melotte 230
Position and the cosmic neighborhood
Caldwell 47 lies within the northern part of the constellation Delphinus, which is a small dolphin-shaped pattern near the celestial equator. The cluster is located away from dense star fields and prominent nebulae, offering a relatively unobstructed view against a richer summer Milky Way backdrop. To locate it, amateur astronomers and astrophotographers often use the nearby bright stars of Delphinus as a guide, as the constellation sits between Sagitta and Equuleus. Its sky position makes it accessible throughout the summer and early autumn months for observers at mid-northern latitudes.
Nice to Know
- Caldwell 47 is known for containing rare “blue straggler” stars, which appear younger and bluer than surrounding stars.
- It was first discovered by William Herschel in 1785, who initially classified it as a nebula.
- The cluster can be resolved into individual stars at the edges when observed or imaged with moderate to large telescopes.
- Its visual appearance is a compact, nearly circular haze, making it a rewarding but somewhat challenging target for deep-sky astrophotography.
Brightnes, distance and size
Caldwell 47 has an average apparent magnitude of 8.8, making it too faint for the naked eye but easily visible in binoculars or a small telescope. It is located about 52,000 light-years away from Earth and spans roughly 85 light-years in diameter. Visually, the cluster appears just under 8 arcminutes across, though astrophotography with deeper exposures can reveal a somewhat larger halo. These characteristics combine to create an impressive, granular core with a smooth fall-off into the surrounding star field when well-captured in images.
