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LONG focus lens???

Started by plunkett, 05/04/2004 07:47AM
Posted 05/04/2004 07:47AM Opening Post
Does anyone know a source for refractor lenses with LONG focal lengths? My club uses a ~5" lens and a diagonal mirror to project a solar image which is in focus about 50 feet away. I guess this would be about an f/120...

Posted 05/04/2004 08:38AM #1
Take a look at D&G Optical. They offer very long f ratio lenses should you desire. They also have a reputation for quality.
Posted 05/04/2004 06:21PM #2

The beauty of the moveable mirror, stationary lens is that you can "launch and leave" it for a while whereas the ep projection method requires constant attention. We were able to leave our setup for about 10 minutes at a time while projecting onto a building with some poster board attached. It's actually quite cool!!! Also, I've "smoked" eyepieces in the past using projection.