Re: ATM A Cage as Secondary Holder

[Daniel Fundo <fundo@bellsouth.net>]

>>> multiple optimized upper ends <<<

<< the pros do this - the several amateur installs that do this that I
have seen all run into the same problem - they do not like to mess with
changing upper ends during the evening observing, so they end up never
changing their upper ends - if someone could work out a good design that
took only seconds to change out, that would really help. >>

At one of the Stellafane gatherings I attended in the early 1970's,
someone had a dual use 16 inch. The Newtonian secondary was about 5.5
inches and the Cassegrainian secondary was a bit smaller.  The owner
could literally change secondaries in seconds. The spider was extremely
ridged (I think it was 0.25 inch brass rod !!!) and the center section
was almost as big as the secondaries.  It had a keyway and a taper
machined in it. A single large thumb screw held the secondary in the
spider.  Two turns of the thumb screw and the secondary slipped out and
could be replaced.  All adjusting was on the removable section of the
mount, of course.  I saw the metamorphosis happen 5-6 times that
evening, and I don't recall anyone commenting about misalignment.  

This was back when no one would think of bringing a commercial
instrument to Stellafane. This telescope was a machinist dream!  It was
all aluminum, stainless steel, chrome and brass.  It was on a wheeled
dolly, and must have weighed close to a ton. I'll look through my old
S&Ts, I think it won the mechanical award that year.

*****-----
Dan F.