ATM Astroscan Houghton

[John Swenson <johnswenson1@attbi.com>]

I recently bought one of the famous Edmund Astroscans (at the new price 
I couldn't resist) but found out it was NOT 1/8 wave parabolic mirror. A 
star test shows severe spherical aberation and a ronchi test shows a 
very nice sphere (it might very well be an 1/8 wave sphere) I haven't 
run an LWT or foucault on it.

Given the spherical nature, I thought well lets make it a Houghton! So I 
did a rough initial design and it looks pretty good in Oslo LT, I need 
some tweaking but it would be a lot better than it is now.

This is going to be my first attempt at lenses rather than mirrors so I 
have a few questions from those that have done this before.

These lenses will be about 4.5" diameter, how thin a lens can I get away 
with? I don't want to add too much weight to the front of the scope so 
20mm thick lenses are out, but can I go down to 6mm thick lenses? I know 
I'll have to put a backing on these to grind and pollish such a thin 
lens, I think I can handle that. But will such a thin lens work in the 
scope or will it be too "flimsy"?

I'd appreciate any experience any have along such lines.

Thanks,

John S.