Re: [ATM] data and musings on thin mirror

[Dale Eason <atmpob@yahoo.com>]

Dave,

What I'm not sure you understand is that even if the
mirror had perfect correction the other errors such as
astigmatism make it an unusable mirror. Even Tasco has
better mirrors I think.  I don't think it could even
be a light bucket.  I think its error is about 14
times worse than Hubble was.  Steve Koehler was going
to generate some simulated images that it would
produce.  Maybe they will demonstrate my point.  If I
can figure out how to input the error into aberrator I
will use it.

The testing you did could never see any of the
astigmatism that is so easy to get when making thin
mirrors.  Foucault done well will measure the
correction and zones but to make a usable ultra thin
mirror you will have to find a test method that can
measure astigmatism.

You have learned how to slump, grind and polish
mirrors, why not learn the easy part, how to test
them.  I enjoy telling my friends who marvel at how a
mirror is made that:

"The marvel is not that we can make mirrors with
extreme accuracy, but that their surface can be
measured accurately to fractions of a wavelength with
stuff you can buy at the hardware store for less than
$10."

Dale Eason


--- vorblesnak@peak.org wrote:

> 
> No, I don't think that was too caustic.  I didn't
> understand the tech
> talk completely, but I thought it was much better
> figured than it has
> been portrayed to be.  I don't like to waste the
> cost of a coating job,
> BUT! I may have.  On the other hand, the mirror was
> slated for service
> as a low power, rich field, light bucket and may
> still work in that
> capacity.  If not, well I will figure some more and
> recoat.
> 
> OR!  My wife, reading over my shoulder as I type,
> would like it for a
> bird bath for her new macrame hanger.  However I
> will resist that
> suggestion as long as I can.
> 
> David Davis
> Toledo, OR 97391
> 
> 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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