Keystone Karte Kurve

[P3D john bercovitz <bercov@xxxxxxxxxxx>]

I've heard the card curvature was to more closely match the 
field curvature of the oculars but I don't know.  I think 
the cards have an awful lot of curvature to them.  I don't 
think the oculars have _that_ much field curvature.  If 
someone wanted to measure the chord and sagitta, he could 
calculate the radius of the card's curvature from:
 
    C^2      S
R = ----- + ---
     8S      2
 
Then Joel could calc the field curvature for a typical Holmes 
ocular, whatever a typical Holmes ocular is.
 
(I have lots of projects for everyone!  8-)  8-)
 
John B


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