The astronomy guys do it all the time. Do a google search for it. However, the quality they need for viewing is pretty far below what most of us would consider acceptable for film. Most of us. I looked into it and wisely got over the urge. The astro folks say they can do it over the course of a few weekends. Longer lens typically have a shallower curvature, so that makes sense. Trying to makea wide angle would probably take a LOT longer, and be less forgiving. I keep thinking someone should be able to make a hypergon-clone at a reasonable cost. It's only two elements. Surely there's a suitable optical plastic that could be easily molded.