|NGC 6885: Open Star Cluster (Vulpecula) RA: 20h 12.0m / DEC: +26° 29'.0|
Instrument: 10-inch Starfinder
Vulpecula is probably best known as home to one of the most awe-inspiring sights in the summer sky. Of course, I'm talking about the magnificent Dumbbell Nebula, M27. However, there are other jewels to see in this neck of the woods. For example, consider the open cluster, NGC 6885, presented in the sketch at left. The brightest member of NGC 6885 is 5.9 magnitude 20 Vulpeculae, which anchors the cluster's core and the center of my sketch. At 129X, the 10-inch Starfinder Newtonian reveals about 50 members of the 8.1 magnitude cluster within a 22' diameter area. The very close pair of 10th and 11th magnitude stars standing 15' northwest of 20 Vulpeculae mark one boundary of NGC 6885. The bright star just inside the norhtern limit of the field of view is 5.5 magnitude 19 Vulpeculae.
Proper identification of this cluster has been a messy issue almost since its discovery by William Herschel more than 200 years ago. According to Archinal, Herschel cataloged two clusters of nearly identical appearance in the vicinity of 20 Vulpeculae. These were identified as NGC 6882 and NGC 6885 in Dreyer's catalog. However, Herschel's descriptions for both objects were almost identical. And there is just the one large, course open cluster which fits Herschel's description. That cluster is NGC 6885.
During his study of galactic clusters in the late 1920s, Robert Trumpler discovered a small knot of stars just northwest of 20 Vulpeculae. Collinder named this grouping, Cr 416. In some circles, this smaller clump of stars has been adopted as NGC 6882. However, Archinal concludes that Cr 416 doesn't fit Herschel's original description. The more likely explanation is that Herschel made an error in recording the same cluster as two different objects, which is not without precedent in the Herschel catalog.
So, the correct identification appears to be NGC 6885=Cr 417=20 Vulpeculae Cluster. NGC 6885 can be found about 5 degrees northeast of the Dumbblell nebula.
Layout, design & revisions © W. D. Ferris
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Revised: January 25, 2003 [WDF]