In view of the length of the development thread on this subject and all the false trails, I'm starting a new thread to describe my working system. I shall be adding to this thread as I collect the details. The camera used was a canon EOS 1100D. This was chosen as having the best chance of producing good results, having the latest Digic 4 image processor with lower noise and extended light gathering range compared with earlier versions. This development actually follows on from my experiments