From: John Swenson 
CC:  atm{at}shore.net
Reply-To: John Swenson 


The Lurie Houghton design has essentially zero coma, zero spherical
aberation and an almost perfectly flat field, it does have a little
astigmatism. The basic geometry is a newtonian with spherical primary and a
corrector right before the secondary (the secondary is usually attached to
the corrector). The corrector consists of two weak lenses that are NOT
achromats, the same glass type can be used for both lenses.

This design can work for fast scopes, you can build an f4 if you like,
although it will take those $200 eyepieces to make the best use of the f4
light cone. You can certainly make a slower one if you want, but the big
advantage is that you CAN make a fast scope that has all these advantages,
it can give spectacular wide field views as well as very good high power
views with the right eyepieces.

John S.

--- BBBS/NT v4.00 MP