I was using the chart in 'Astronomy Now' and knew that Io was due to go behind Jupiter's limb at 20:51 and my grandiose plan was to see if I could capture an image of Jupiter with Io very close by. I captured my first avi at 21:05 and I could see no sign of Io in a playback so I thought that the fov was too small for Io to be in the frame. My second avi at 21:30 showed Jupiter to be quite dim and hence my discovery of the dewing problem.
I never got to try out a Barlow and indeed the focus was a manual effort ( the electric focusser was making/breaking contact).
I had a couple of practice runs with registax5 and it was only tonight when I spent more time playing with the settings that I noticed that Io was in the frame (left edge centre). I realise the image is on the grainy side but I do not know if it is well focussed.
We get so few decent nights for observing and it seems that most of those are curtailed by dewing so I really would appreciate any advice on a good system to deal with dewing.