Hi Tony, The Norden was an American high altidude sight and not used by 617. They did experiment with chinagraph marks on the nose blister, a triangular peice of wood with three nails in it and several other types of crude sight suitable for the low level raid on the dams. The problem was that they needed to get height, heading and distance from the Dams right when they dropped. They probably did try coathangers as well but the triangle seems to have been the most popular on the Dams with towers. Best regards. T

Re:- Bomb sight .. My late father (Jack Grace) was a pioneer aviation engineer (starting with Alcock & Brown's Vimy!)who worked for Vickers, later Vickers Armstrong. During the war he was stationed all around Britain repairing, modifying and servicing the R.A.F's Wellington bombers for wartime duties. He was also involved with Barnes Wallis on the development of suitably accurate aiming sights for the bouncing bomb project as he was an ingenious natural engineer and mathematician.I am almost certain that original development/trials took place using Wellingtons. I also know that numerous odd assortments of wire and strip metal frames, triangular in shape were lined up in our garage. Aged 5 or so, I neither asked questions about their purpose nor would the answers, if given, have meant much to me at the time! I do know that after the war at the early Farnborough Air Shows, the two men would often meet up and chat.
My father introduced me to Barnes Wallis and explained that he had made great achievements to date in his life and that I would one day recall having met such a famous man. An under-rated genius.