From: "Cary Chleborad" 
To: "John Sherman" , 
Reply-To: "Cary Chleborad" 



No one number alone can quantify the performance of a mirror.  John is
starting to hit upon this idea, however I think the numbers that really
need to be considered are Transverse error (which nobody talks about)  and
Strehl ratio in combination.  Forget p-v - it's near totally meaningless.

-Cary


>
> Mark wrote:
> > This has been a much debated topic, but the mathematical answer
> >is that there can be fairly large  differences in RMS and Strehl
> >compared to P-V.  Also, the mathematical answer  is that RMS
> >(and Strehl) is the better number to base decisions on.
>
snip

> I do not disagree with Mark's statements, but my experience does put some
> level of doubt into the mix. My current thinking is that the P-V is about
as
> important as the Strehl ratio (&RMS). If you have a good Strehl but a bad
> P-V, then something is wrong and needs to be fixed.
>

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