Re: [ATM] Re:How much of cell induced deformation is too much?

["john sherman" <atm@mail.johnspics.com>]

Hi Vlad,

>I finally got to answer.

Yes, I was watching for the weather report the other nite and they showed floods and rain in your area. I hope you and yours are okay.


>By definition, 50% Strehl means that central 
>intensity of the Airy pattern is reduced by 50% 

Yup, that's what I thought. 

>That still leaves us with ~50% energy out of the Airy disc.

So what is the % of light in the Airy disc for a perfect aperture? I'm thinking it's 86%, but I don't have any books here with me (maybe I should go read one?<g>). So 50% of that would mean there is 43% of the total left in the disc, and therefore 57% elsewhere. Right? So if I look at a star in my scope the rings and background should appear bright compared to the disc. Right? So why is it that when I look in my scopes the disc appears to be very much brighter than the rings and background? Wouldn't this observation indicate that I am getting much better than 50% final Sr out of my scopes? I know the disc is concentrated into a smaller area, but still...


>it may be at least as important to have a cell that can 
>be made to highest standards, as it is to have one that 
>gives the least amount of deformation 

Ya, that's pretty much what I thought.

Thanks,

John


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