Re: ATM truss bending calculations (long)

[Aplanatic@aol.com]

Don wrote:

> This line of reasoning is following the path that Serrurier was following;
>  That a telescope truss can never be perfectly rigid. Serrurier's solution
>  was to let the primary and secondary sag, but both by the same amount and
>  thus maintain collimation.

Serrurier trusses are designed to sag in such a way that the top and 
bottom end members stay perpendicular to the original optical axis, 
which also has to be true to maintain alignment.  Very clever indeed.  

I highly recommend the book "The Perfect Machine," which is a delight 
to read if you are interested in telescope design and fabrication.  
There are some truly interesting stories about making the first Pyrex 
mirror blanks, transporting the blanks, designing and building the 200" 
telescope (including Serrurier and his truss) and a host of other amusing 
tales.  For instance, do you know how long it took to build the Hale 
telescope?  Even longer, I imagine, than most ATMs take to grind their
first ones.

Dave Rowe