Re: [ATM] Mirror cell for an 8" mirror

["Olivier Biot" <olivier.biot@gmail.com>]

On 11/4/07, Mark Holm <mdholm@telerama.com> wrote:
>
> In my not so humble opinion, a K&B style tailgate isn't such a hot
> design for an 8 inch mirror.  It's main strengths (lightness, stiffness
> and relative ease of construction for the lightness and stiffness
> obtained) really only become important at larger sizes.  One of it's big
> weaknesses is putting the collimation adjustments at the same radius as
> the mirror supports.  When you accept the fact that a 3-point cell is
> optimal for 8-inch and smaller mirrors and that the optimum is at 40%
> radius, you need to start thinking about decoupling the mirror support
> function from the alignment function.  Think about it for a while.  It
> is actually much simpler than it sounds.

About 8 years ago I successfully failed in building my 1st "classical"
9 points cell by using the same bolts for mirror support *and*
collimation. It was overly complex and plainly not working in my
situation. I have then put my ATM project to rest for a couple years.

Since then I've only been considering cells where collimation and cell
support functions were decoupled from eachother. Seemingly more
difficult but in practice much simpler. When doing so, you can
*decide* where to put the collimation bolts on the frame that supports
the cell. If you want, arranging the collimation bolts can then be
very easily done in a 90 degree configuration (as opposed to the more
traditional 120 degree configuration in symmetrical cells that reduce
to 3 points). Think of the collimation bolt in the right angle of this
setup as a pivot point or a joint that you normally do not need to
touch (unless you want to move the primary up/down along the optical
axis).

Cheers,

Olivier
_______________________________________________
ATM mailing list http://www.atmlist.net/