Re: ATM Houghton-Newtonian a.k.a. Closed Tube Telescope

[behambu@teleline.es (Berthold Hamburger)]

>
>Would doing that not require a focuser with larger than average travel. Say
>three inches versus one inch.
>
>David H. Bevel

Not if you use a sliding focuser. Especially for small scopes I thinkk
it is the best way to go, as you minimize focuser height, diagonal
size (and weight).

With an oversized tube one might even consider haven the focuser
carriage ride INSIDE the tube. That way there would not be a problem
with vignetting at the focuser by still gaining the advanteges of a
big tube. 
Has anyone ever tried this?

BTW, I am in the planning stages for a 6"/F3.5 Lurie-Houghton and
would like to hear some input regarding glass for the corrector. Does
it have to be BK7 or would Waterwhite plate or selected Plate glass
(Newport) be fine as well.

Berthold

                        -------------------
Berthold Hamburger - Cellist
InterNet: b-hamburger@teleline.es
Homepage: http://www.geocities.com/CapeCanaveral/9601