Re Viewer interocular

[P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>]

Thanks to Greg Kane for his post in digest 2051/2 I am now clear I think on
what he means by the term "Optical centre" IE the centre of the diameter of
the original lens from which the lenses for a Brewster/Holmes type
stereoscope are cut. My problem was that I am more familiar with "Optical
Centre" as meaning the centre of the lens through its thickness as
determined by the way I outlined in my original post which would also
correspond to the centre of the lens diameter. But for measuring focal
lenth from this point it would only be neccessary to measure from the plane
of the optical centre so it need not correspond to the centre of the
diameter.     P.J.Homer



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