To: 
From: Mark Suchting 
Reply-To: Mark Suchting 


At 10:08 AM 16/02/2003 -0800, John Sherman wrote:


>You mount the objective near the top (sky end) of the tube. You put a 5"
>flat at the bottom of the tube. You put a 2" diagonal flat at the top of the
>tube (next to the objective), which reflects the light out sideways to the
>eyepiece.


I think building a folded system partly defeats the advantages of the
refractor in the sense that the poorer contrast of the same in a Newt is
partly due to scattering and light loss in the aluminium coatings, an
advantage that may be lost in a folded instrument.

I suggest this becasue I was recently amazed in setting up my  16 X 70mm 
binoculars against a quality overcoated zerodur flat to `save my neck' one
night , at the contrast and light loss of just one reflecting surface.
Threshold detail and contrast in clusters and nebulae were unmistakeably
lost with just one reflection. In the case of say a Newt binoclar we can't
avoid an extra reflection but in a refractor I would try to avoid any extra
reflections. A long focus Newt of slightly bigger aperture , with small
secondary and good  baffling might be a lot easier and cheaper  to make
than a folded refractor?

~Mark

--- BBBS/NT v4.00 MP