Re: ATM Moving Mirror Focuser

[andydtg@alpha1.phoenix.net]

Donald Clement wrote:
>       This is a description of a moving mirror focuser that I just 
>     completed this weekend for an 8" F10 Maksutov Cassegrain. The focuser 
>     consists of three 1/2" x 20TPI threaded rods fixed to a 3/4" plate on 
>     a 7" diameter... (etc)

Actually, the early models of the Celestron 16" S-C used a focusing mechanism 
like this. We had one at the NASA JSC Tracking lab & found it had problems with
focus wobble and boresight shifting as the scope elevation changed. It was
replaced with a fixed mount, with focusing done by moving the secondary on
a leadscrew and ball bearing bushing.

More recently (early 90's) I built a large eyepiece turret for the Danciger 32" 
scope which incorporated a 3-screw focuser in its base. This used 1/4"
roller chain
and sprockets instead of a timing belt & could easily support the 10+ pound
weight of
the turret and 4 2" eyepieces. Not a trivial thing to build, though!

Andy Saulietis / DTG Alt-Az-Fp Drive Systems
12617 Harriet Ln
Santa Fe, TX 77510 USA
409-925-8854 Voice/Fax