When the cloud eventually cleared I had more success with the M 51 supernova than I expected. A rebalance of my system to favour post-meridian tracking and a change of guiding camera worked well and I was able to obtain more subs than I thought possible before M 51 disappeared behind the observatory roof....Changing the guiding webcam appears to have been a very positive step with an immediate improvement in guiding accuracy. Some time ago I purchased a Logitech Pro 9000 for general webcam work noting it offered a resolution of 1600x1200 pixels. As a normal webcam the quality was very good and I pondered how good it might be converted for astronomic use. When I came across this helpful site I took the plunge and once more found myself at Maplins buying the neccessary bits to make the conversion. Though a bit more testing is needed it already looks as though my old faithful Philips cam is facing retirement. Details for sn2011dh: 10" f4.3 Newt. 10x 5minute exposures @ iso1600 with CLS in DSS, FIV, CS2 & XAT.