Maybe it’s an area of reduced stellar population within the globular, or perhaps thin dust lanes slightly masking our view. Whatever it is, the dark propeller or Y-shaped feature in the Hercules Globular Cluster is real. When I saw it the first time with Khalid sahab’s 18″ at Lake Kalri in February 2010, it was hit-me-on-the-head obvious.
Although it is said that the feature is easier to observe with smaller apertures than with larger ones, I’ve yet to see it with the 10″ LX200. Give it a try and see for yourself.
Here’s a shot of M13 by Hunter Wilson.
Another image. Courtesy Emanuele Colognato
