Sorry about the picture David, not too sure what is going on there!
At last autumn’s Kielder star party an excellent talk was given by Professor Andy Newsam highlighting the work of the highly successful Liverpool telescope. The secondary mirror for the telescope was made by the Sinden Optical Company, it is about 60cm in diameter and is convex in shape which makes it very difficult to test as such a mirror does not form a real image. In addition the surface has a shape described as hyperbolic. Such optical components are renowned for being difficult to make. Had David been sitting in the audience that day he would have had good reason to be satisfied with his contribution to the Liverpool Telescope and its part in the advancement of astronomy.
For more information about the Liverpool telescope look here.. http://telescope.livjm.ac.uk/
John