M13 is a Shapley-Sawyer Class V globular cluster lying 25,000 light-years from Earth in the constellation of Hercules. An interesting feature of M13 is the Y-shaped dark lanes in the upper left portion of the cluster. This was first noted by Binden Stoney using Lord Rosse's 72-inch reflector at Birr Castle, Ireland in the 1850s. It is now referred to as "The Propeller" due to its resemblance to a propeller with three blades. It is debated whether the propeller is due to obscuring material in the cluster blocking our view of stars behind it, or due simply to zones with fewer stars. However, it has been known since the early 1960s that globular clusters do contain dark obscuring nebulosity material, so the former theory is favored. The CDK 17 resolved this feature very clearly as well as resolved countless stars in the core of M13. The small galaxy at the upper right is IC 4617, which lies at a distance of 553 million-light years, which gives an incredible depth of field to the image.

Exposures: L:R:G:B = 245:40:40:40 minutes =6 hours, 5 minutes total exposure at f/6.8.