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    Re: How does the AstraIIIb split mirror work?
    From: Jim Thompson
    Date: 2004 Apr 27, 07:06 -0300

    > -----Original Message-----
    > From:  Trevor J. Kenchington
    > Are some horizon mirrors given low-reflectivity coatings?
    I have been wondering in fact whether the clear glass portion of this mirror
    has a slight increased reflectivity coating of some kind that allows plenty
    of light to come through the glass from the horizon, but also allows more
    reflection of the index mirror's image from the clear glass than plain glass
    alone?  This would create the effect that I have been enjoying with this
    traditional split mirror add-on that I bought from Celestaire a couple of
    weeks ago: persistence of the index mirror's image over the clear glass
    portion.  I had anticipated that the celestial body would disappear at the
    center of the FOV.  This phenomenon is what started this thread, which has
    been very educational.

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