Re: [atm_free] RE: [ATM] Mirror Round Robin and some in-house testresults

["James Lerch" <jlerch1@tampabay.rr.com>]

----- Original Message ----- 
From: "Scott Milligan" <starzkey@charter.net>


>
> James:
>
> Yes, very interesting indeed.  A fast look at the results suggests that
> reasonable agreement between Foucault and interferometry exists when
> astigmatism is not the largest error present (cylinder and or trefoil).

Scott, I think this is how it should be, if the optic is truely a figure of 
revolution, then Foucault and Interferometry should agree..

> Robo-Foucault seems to be "out in left field", however, and optimistic every
> time.  Do you share the same conclusions?

No, not really, and it depends...

Starting with the three mirror round robin optics.  I'd say the 15 zone Robo and 
Couder Mask testing are nearly the same on mirrors A & C, with Robo being a bit 
under-optimistic compared with Couder mask results.

With regards to Mirror B, it was the thinnest of all three mirrors, and didn't 
appear to be fabricated from either plate or Pyrex substrate.  I noted on my 
original report, as well as on the spread sheet, that I had a hard time testing 
this optic.  Perhaps it didn't like the changing temperatures of my Florida 
climate, and or it didn't like my test stand... In any event, both my Robo and 
Interferometry results seem to be outside the norm for this thin optic.

With regards to the remaining six optics I've tested in house.  Three of the 
optics have non rotationally symmetric errors, and in such cases we would expect 
a two dimensional test like Robo (or any KE test) to most likely be 
overoptimistic on the results.  However three of the six optics were fairly 
rotationally symmetric, and in such cases the robo v interferometry results seem 
to comply

Ron's 6" F/7.7  Robo = 0.99 Strehl, Inter = 0.98 Strehl

Don's 10" F/5.6 Robo = 0.88 Strehl, Inter = 0.86 Strehl

Charlie's 12.5 F/4.5  Robo = 0.84 Strehl, Inter = 0.84 Strehl

The remaining three mirrors all had various amounts of Tre-Foil error, and Robo 
did indeed report a rather over optimistic result for these optics.

Finally, its just about impossible to compare P-V wave front errors between 2 
dimensional tests (like Robo and Couder Mask) with 3 dimensional tests like 
fringe traced or phase shifted interferometry.  (with the caveat that Roger 
Ceragioli's software has the ability to manufacture a rotationally averaged P-V 
wave front result, which should/could/might compare to 2 dimensional tests..

Take Care,
James Lerch
http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site)

"Anything that can happen, will happen" -Stephen Pollock from:
"Particle Physics for Non-Physicists: A Tour of the Microcosmos"

" Press on: nothing in the world can take the place of perseverance.
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                                                           Calvin Coolidge





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