P3D Re: Diffusers

[Tom Hubin <thubin@xxxxxxxxx>]

Bob_Maxey@xxxxxxxx wrote:
> 
> Consider the tried and true materials such as flashed opal glass and frosted
> glass. Both are perfect and easy to locate.
> 
> RM

Hello Bob,

They diffuse too much. Ususally a full hemisphere. You need this if
there is no condenser lens. But if you use a condenser lens then you
only need to diffuse enough to fill your eyepiece. For an f/2 eyepiece
that would be a 28 degree cone. That is only 1/64 of a hemisphere. In
other words, 64 times as much light at the eyepiece with very little
light wasted illuminating the full interior of the box.  

You can do even better if you diffuse 28 degrees horizontally and no
vertical diffussion. Should give another factor of 4 to 10. The only
reason to diffuse at all is to provide light to the pupils for a variety
of interoculars. No reason fopr vertical diffusion.

Tom Hubin
thubin@xxxxxxxxx