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    Re: Sextants with Polarizing filters
    From: Peter Fogg
    Date: 2006 Jan 26, 19:54 +1100

    > > lightbox (a sheet of well-lit white paper will do):
    Bill wrote:
    > A caution if trying this at home. If using a "well-lit" sheet of white
    > paper
    > (front instead of back lighted) and laying the filter on the paper, the
    > density/color shift of a normal filter will double.  Light has to pass
    > through the filter to reach the paper, then the light reaching the paper
    > is
    > reflected by the paper--back through the filter--to reach the observer.
    > How
    > might this work with a polarizing filter? I am fearful of hazarding a
    > guess.
    I wouldn't want to make too much of this. The white paper was only
    introduced for the benefit of most of us who have no access to a lightbox.
    The filters need to be held above the paper so that the filter densities/
    colours can be compared. Polarizing sunglasses can be used, as far as I
    know, for these polarizing experiments.

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