Re: [ATM] (Long) How good is good enough? (was how muchcelldeformation is too much?)

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

Hi Scott,

>rated in the laboratory as diffraction limited (as evidenced by a >Strehl ratio evaluation > 0.8), and optics that test measurably 
>better than that

Ah, but is 80% Sr REALLY diffraction-limited? And if so, why can we see the difference when optics are made better than that?



>Now I realize that anything like a controlled experiment designed to 
>answer the question at what point (figure accuracy vs. aperture) 
>should a visual observer stop worrying about optical quality issues 
>is probably not achievable by a group of individuals scattered 
>across time and space. 

>1. Some attempt should be made to quantify and communicate the 
>atmospheric seeing limit FOR THE APERTURE BEING USED to report the 
>observation. 

Indeed, trying to decide on standards verbally is likely to be futile. So that's why I believe the best way is to set up a bunch of scopes together, and do side-by-side testing. It reduces the variability of the subjective rating of the atmosphere. What one person thinks is excellent seeing is bad enough to make the other person go indoors and watch tv. 

Your other four points are also very important to the cause (I think that is part of the reason for the mirror-testing round-robin which has been ongoing for a while). And still the best way I know of are side-by-side comparisons, so each issue can be equalized as much as possible. 

I will try to join in your experiment, but it just doesn't seem doable by emails.

Are you in or near California?

>Thanks for taking the time to read this. 

Thanks for writing it.

John



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