Re: (ATM) Best way to mount a secondary ?

[Mark Suchting <masuch@dap.CSIRO.AU>]

On Thu, 19 Oct 1995, Bratislav Curcic wrote:

> >> mounting a 5" diameter secondary for R-C
> 
> Sounds like serious stuff ... I'd play it safe and make clip holders
> a'la Texerau. Silicon is good stuff, but Cassegrain (sorry,
> Cassegrainian :-) is notoriously sensitive to miscollimation. A fast
> primary and a fair amount of magnification on secondary will make it
> HUNDREDS of times more sensitive than an equivalent Newtonian ! A
> miniscule increase in diffraction is a small price to pay for a peace
> of mind.

When we mounted the 8" secondary for the 24" RC CASS at Nepean, I sat the 
secondary in its holder sitting on 3 ball bearings at the 70% zone with a 
blob of RTV next to each ball. The four mirror clips ( it has a 4 vane 
secondary holder ) were then providing lateral support and the front 
retainers sat a mm above the secondary surface, purely for peace of mind. 
With this system then, we had a stress free holding of the secondary, 
with the positivity of metal against glass for maintainence of 
collimation. The system works very well....

mark