I put together a sheet of various-sized annular shadow casters, and posted it in GIF format to (one of) my archive sites. (The other is too damned busy to let me ftp into it for the last couple of hours!) Download the files and print on overhead projector acetate. There are 5 rows, each half-scale to the adjacent row, and 5 columns, each with a different ratio of central obstruction radius to outer radius. I haven't had a chance to test them yet, as it's somewhat hazy here today; maybe later!
Dave Bell N37.28W121.96 http://dialist.webjump.com/ http://www.crosswinds.net/~dialist/ (Once I can get them uploaded!)
