RE: [ATM] RE:Flats -subap. -(was annealing)

[Ric Rokosz <radicell2@yahoo.com>]

--- Scott Milligan <starzkey@charter.net> wrote:

> Clever idea.  That would be one heck of a sturdy
> rail & carriage.  In fact,
> I wonder if it might not be easier to just break
> down and make the large
> flat?  I'm guessing an answer to that one probably
> depends on how you define
> large, and what you have available to work with.
> 

It seems you might be making things more difficult
than necessary.When testing my 18 inch f/2.8 primary I
setup the 12 inch flat I had to see what type of null
I had figured onto it by way of the Ross,plus just to
play around with a subapeture flat that I had read the
pros use  in some of the pro article.
The flat was on a wooden mount,the Fou tester riding
on it aswell.To image the 18,I just slid the wooden
mount left or right to see sections of the 18's
surface.Since I had used the Ross lens in a null setup
I knew what the null figure ought to look like and the
view with the subapeture flat was the same.Ronchi
gratings made things easy.

This same experiment was done with a finished 14 inch
f/5 mirror.

Ric

> 
> >It IS NOT NECESSARY  to use a full aperture flat to
> test a primary mirror.
> 
> 
> One could put the subaperture flat on a sliding
> kinematic
> carriage, with the usual tilt adjustments on the
> flat.
> The flat is aligned to the primary positioned to be
> concentric
> with the primary, then slid laterally to view the
> surface
> between the edge and center of the primary. Note
> that the slide
> does not neer to be aligned to the optical axis,
> just that it
> traverses without changing the normal to flat.
> 
> Andy Saulietis



		
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