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    Re: Advice concerning sextants
    From: Ken Gebhart
    Date: 2010 Feb 23, 11:15 -0600

    I would like to make two comments about Jim's posts:
    1.  Bigger mirrors do not give more light. (Is your image while
    shaving with a large bathroom mirror brighter than with a small one?)
    2.  Whole horizon mirrors do not divide the light.  They have a
    specialized coating which transmits a large percentage of light,
    while at the same time reflects a large percentage of light.
    
    Ken
    On Feb 22, 2010, at 11:40 PM, James N Wilson wrote:
    
    > John reminds me of my first experience with the whole horizon sextant
    > mirror, which I called the half silvered mirror, was that finding the
    > horizon in dim light was difficult. I found no advantages, in that the
    > sun and moon images can be seen in the clear part of the mirror,
    > aiding
    > in bringing them down.
    >
    > Now, if someone would make a horizon mirror that was half silvered on
    > only the left side, that might be worth something. But I might
    > still have
    > the same problem at twilight, where I need all the light available
    > to see
    > the horizon.
    >
    > I'm sure that the article mentioned noted that half silvered
    > mirrors (one
    > way glass) allow only a portion of the light to pass. When we
    > remodeled
    > our bath, we had one installed in our shower for privacy. The room was
    > significantly darkened, and plants wouldn't grow. The amount of light
    > reduction is significant.
    >
    > Jim Wilson
    > ____________________________________________________________
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