Re: ATM Re: Aplanats II via troublesome Juno X-mailer

[John Swenson <johnswenson1@attbi.com>]

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.