NGC 6645 is a most interesting summer time cluster located in the constellation of Sagittarius.  Upon careful examination with either my 102 mm Orion/ Vixen refractor, or my 10-inch Newtonian reflector, a small hole, devoid of stars can be seen in the middle of the cluster.  

Please click on the following link and read more about this fabulous deep-sky in an article for Orion Telescope and Binoculars.  

http://www.telescope.com/August-Deep-Sky-Challenge-Open-Cluster-NGC-6645/p/103242.uts

Roger Ivester

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