NGC 6934, also known as Caldwell 47, is a 9th magnitude globular cluster located in Delphinus. Backyard scopes show a fuzzy disk of nebulosity, about 5 arc minutes in diameter with a brighter core. The globular is not visually spectacular, but that's due to distance and not intrinsic brightness. At 50,000 light-years, it's one of the more remote globulars easily seen with amateur scopes.
William Herschel discovered NGC 6394 on September 24, 1785. He classified it as a "bright nebula" but wasn't able to resolve any stars.
The cluster is best seen during the months of July, August and September. It has a spatial diameter of 120 light-years and is estimated to contain about 250,000 stars. It's believed to be around 10 billion years old.
NGC 6934 is located 4 degrees south of Epsilon Delphini (mag. +4.0) and 1 degree northwest of a pair of 6th and 7th magnitude stars. The globular is a difficult binocular object, ideally requiring dark skies. A small 80mm (3.1-inch) refractor shows a faint, clearly non-stellar circular patch of light. Just to the west of the cluster is a 9th mag. star.
NGC 6934 can be partially resolved with a 300mm (12-inch) telescope. At about 200x magnification dozens of stars are revealed, especially on nights of good seeing. The cluster appears compressed and grainy. A very large 450mm (18-inch) scope at high powers will resolve some of the stars at the core. Photographically, NGC 6934 spans some 8.4 arc minutes across but visually it appears a few arc minutes less.
In Delphinus there is an even more distant globular, NGC 7006. It's located about 10 degrees to the northeast of NGC 6934 and at 135,000 light-years, is nearly three times further away.
NGC 6934 Data Table
|Object Type||Globular Cluster|
|RA (J2000)||20h 34m 11s|
|DEC (J2000)||+07d 24m 16s|
|Apparent Size (arc mins)||8.4|
|Age (years)||10 Billion|
|Number of Stars||250,000|