Re: [APML] Ash Lurie Schmidt alternative

[Aplanatic@aol.com]

Hi Robert,

> I have had a Celestron Schmidt for over 20 years and I have never had a
>  problem with vignetting.  The manual that came with it says it 
theoretically
>  vignets 15%, but I have never seen it.

A ray trace shows 15% vignetting 0.5" off-axis with an 8" primary and 33% 
vignetting at an off-axis distance of 1" (for a 50 mm film holder).  I've 
found with TechPan that 25% vigetting is quite noticeable and hard to remove, 
but with color film it's not much of a problem.  So I guess it depends on the 
size of the film and the type of film.

Dave Rowe

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