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Re: [ATM] Accuracy of Mahajan's approximation for Strehl ratio

Michael Peck wrote:

> At 13:29 8/15/05, Koehler, Steve wrote:
>
>> You note that Mahajan is pessimistic for larger RMS errors.  Is it 
>> possible that
>> your directly calculated Strehl ratio is inaccurate (optimistic?) for 
>> larger RMS
>> errors, because the calculation is discrete?
>>
>
> Steve:
>
> Maybe. I guess the way to find out is to use a larger FFT. I think I 
> have enough memory to try it, and CPU cycles are cheap.
>
> Mike
>
FYI I've found that ZEMAX doesn't approach OSLO's result for Strehl 
until at least
256x256; at that point it is off by about 0.02 at 0.8 Strehl.  You may 
have to go up
to at least 1Kx1K.
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