On 9/14/05, J. C. O'Connell <[EMAIL PROTECTED]> wrote: > > I was thinking about this again this morning and I believe there was a > misunderstanding > on the discussion of the parallelism of the suns rays with regards to > optics. > > While yes the sun itself is not seen as a point source of light ( its about > 1/2 a degree > angularly in the sky ), the discussion wasn't really about the angular > dimension > of sun in the sky, it was about how parallel a point of light eminating from > the sun is entering > (exiting?) a lens system on earth. > > I just calculated that a single point of light from the sun which is ~93 > million > miles away from earth surface, hitting a lens with a diameter of say 3 > inches > creates a slight angle, of course not truly parallel, but this angle > calculates > to 0.0292 BILLIONTHS of one degree! So for all practical purposes a point of > light from the sun > will create rays that appear virtually parallel to just about any optical > system on earth. > Even if you had a lens as big at earth itself in diamter, the parallelism > of the rays entering aross that lens would still be less than 3 thousandths > of a degree > from any point of light coming from the sun. And that's a lens with filter > size = PLANET EARTH.
If the lens isn't super multi coated, it might flare. <g> cheers, frank -- "Sharpness is a bourgeois concept." -Henri Cartier-Bresson
