Re: [APML] needed- an excellent sense of direction

[Aplanatic@aol.com]

Hi Torsten,

> If the camera film plane (oag, T-ring, camera body, etc) is square to the
>  drawtube, and a star test image in a high-power eyepiece (assuming the
>  eyepiece isn't skewed either) is perfectly round, then the film plane
>  should automatically be perpendicular to the optical axis.

Yes, I believe so.  At least I can't think up a counter example.  But in 
practice using this technique to collimate the optics is not a good idea, I 
think.  For example, if an aberration grows quadradically with off-axis 
distance then there is a large sweet spot near the optical axis that 
essentially tells you nothing about collimation or image quality near the 
edge.

Dave Rowe

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