Re: ATM 14.5.I.S..........secondary

["Richard Schwartz" <richas@idt.net>]

> > what size secondary do i need?
> > the focal legnth is 72 5/8" now that its

the anser is 1.2" +   x / 5

x is the distance from the focal plane to the senter axes of yer tube.  the
focault plane is usually somewhere around the bottom of the sliding
in-and-out thing where you look.

so, if x is 8", the secondary is 1.25 + 8/5 = 2.8".

if  you cant afford such a big flat, just use one that is smaller and tell
everybody that you did it to minimize diffraction.  they will all be
impressed!