[ATM] (no subject)

["Jerry" <wa4guu@verizon.net>]

-----Original Message-----
From: hermit



 

John Moore wrote:

 

> 

>Ive studied the archives now for 2-weeks, Alot! has changed since I left

>in the early 80's,WOW!!,,The Knowledge has expanded a hundred-fold!

> 

>  

>

The one thing that has not changed is that bench testing is for getting 

atm's close enough to star test the mirror.  The testing method will 

never be the magic bullet in figuring.  ;-)

 

Ken

 

 

You are either extremely good at star testing or extremely poor at bench
testing.

 

I get dead on bench testing and prove that I'm somewhere in the neighborhood
by star testing.

 

 

 

To answer John's question... How well can you read a null? How small of a
deviation from perfect would result in you determining that you did not have
a null? If you had a steady deviation of the curve from center to edge that
totaled 1/20th wave could you tell? If not you could see a null and be
1/20th wave wrong. That could add to the 1/20 wave on the reference. And it
can be complicated by where the errors are on the reference and where the
errors are on the mirror under test.

 

There is no easy exact answer. 

 

Jerry

 

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