Re: 2066 Viewer lens quality

[elliotb@xxxxxxxxxxxxx (Elliot M Burke )]

Paul Baker writes:

>I am disappointed in the quality -- I consider the Red-button's achromats
>to be the best of the vintage originals and was expecting even better
>performance from _double_ achromats (ignorantly, I guess, because I don't
>study optics and assumed "two must be better than one").  But I notice a
>lot of what I call "swimming" distortion as I move my eyes around to take
>in the entire image (I wear glasses so my eyes are never really close to
>_any_ viewer's lenses to begin with :-).

You might be noticing pupil aberration: movement of the exit pupil with axial 
movement of the eye.  With lateral motion and pupil aberration really odd 
things happen.  With a projector type system one source of the problem may be 
the illumination optics.  Put a white card where your eye usually goes and look 
at the pattern of illumination.  There will be a disk of light.  Move it 
axially and see what happens.  Maybe a diffuser is out of place?  Or it could 
be a design flaw.

Eyepieces of the dual achromat type are refered to as the Plossel type and can 
be extremely well corrected, are usually well corrected for most aberrations.  




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