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Re: [ATM] secondary size dillemma


Hi There,

> a 0.21mm 100%illuminated field of view 
>with a16% central obstruction.

Does anyone know why an undersized secondary always seems to increase contrast in the image? I can understand if the small secondary is vignetting away a TDE or un-blackened bevel, that would certainly be an improvement. Or is it just the smaller obstruction? Does going from 19% to 16% really make enough difference to the diffraction to give a noticeable contrast increase? 

Thanks,

John







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