Last night I managed 16 x 5-minute subs on the Double Cluster region using the Canon 200mm lens with the M25C OSC and a 52mm IDAS filter on the front of the lens.  The filter stops the lens down to f#3.85 with the native lens diaphragm wide open – hence no 8-pointed diffraction spikes 🙂  Lots of water vapour in the air – but fortunately no Moon.