NGC 6940 is a rich, well-populated open cluster that stands out due to its large angular size and bright appearance against the Milky Way background. Amateur astrophotographers appreciate its wide distribution of stars, making it an appealing target for wide-field imaging. The cluster is not very young, with an estimated age of nearly one billion years, resulting in an appealing population of red giant stars. Its loose, well-resolved structure provides striking detail even through modest telescopes or using standard DSLR cameras.
Names and Catalog numbers
- Trivial Name: There is currently no widely accepted trivial name for NGC 6940.
- NGC: NGC 6940
- Melotte: Melotte 232
Position and the cosmic neighborhood
NGC 6940 resides in the northern constellation Vulpecula, relatively near the celestial equator, making it accessible to observers in both hemispheres. It lies in a dense region of the Milky Way, a short distance east of the well-known “Coathanger” asterism (Brocchi’s Cluster). The cluster is distinguished from nearby deep sky objects by its loose, scattered assembly of mid-to-faint stars, many sporting a yellow to red hue indicative of its age. It is not associated with any bright nebulae, and large dark nebulae in the vicinity frame its glow, providing contrast for astrophotographic work.
Nice to Know
- NGC 6940 is often considered one of the richest open clusters not included in major Messier or Caldwell lists, giving it a “hidden gem” status among astrophotographers.
- The cluster’s age conveys a noticeable population of red giants, which provide a pleasing palette of colors in long-exposure photographs.
- NGC 6940 is large enough that it is best captured with a short focal length telescope or camera lens, making it an ideal subject for wide-field imaging setups.
- The absence of interstellar gas or unresolved core allows almost every star within the cluster to be distinctly captured, enhancing detail for both visual observers and imagers.
Brightnes, distance and size
NGC 6940 shines at an apparent magnitude of around 6.3, making it easily visible with binoculars and a subtle highlight to the naked eye under dark skies. It lies approximately 2,500 light-years from Earth, placing it comfortably within our Milky Way galaxy. The physical diameter of the cluster spans about 16 light-years across, while its angular size in the night sky is roughly 31 arcminutes—just slightly larger than the apparent diameter of the full Moon. These features combine to make it an impressive open cluster for visual and photographic observation.
