Jefferson wrote: > Andrew Janssen wrote: > > >>The website I got a lot of heliograph information from is: >> >>http://myweb.cableone.net/kd7aoi/ >> >> From the pictures of the American Service heliograph and the British >>Mance heliograph, it seems pretty clear that the mirrors are in fact >>flat. > > > The American Service heliograph is a drawing, not a photograph. The British > and Portuguese heliographs are clearly parabolic. Look at the circular > patterns on the reflective surfaces. A flat mirror would show either lines or > waves. I might be willing to grant you the British, but I don't think you can tell about the Portugese. The image quality isn't great. Andrew > >>There's also a reference under one of the subsidiary links to the >>American heliograph, 4in mirror, being bright enough to hurt the naked >>eye at forty miles away. > > > Then it has to be parabolic. Ordinary reflected sunlight is not dangerous at > that range. I didn't say it was dangerous, just that it hurt. Andrew > Jefferson > http://www.picotech.net/~jeff_wilson63/rpg/ > > > > ---------------------------------------------------------------- > To unsubscribe, send mail to celandra-off@phoenyx.net. > ---------------------------------------------------------------- To unsubscribe, send mail to celandra-off@phoenyx.net.
