Mercury Transit - 160509 - 4 minute overlay as shot

After aligning all of the photos but before rotating them to correct for the alt-az scope motion, I thought the result looked pretty cool, so decided to keep a copy of this as well. In this one I left the one frame with the spec in it. Someone else caught a transit of the ISS around this time, I but I don't think I was in a position for this to be that. Not sure what it was!