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    Re: Sextants with Polarizing filters
    From: Yanni Nikopoulos
    Date: 2006 Jan 26, 23:21 -0500

    It also means "correct" Thus "right" which the translation
    to the English language as "right"
    Yanni
    Marinated
    S/V Princess Thalia
    Hamilton
    ----- Original Message -----
    From: "Bill" 
    To: 
    Sent: Thursday, January 26, 2006 11:09 PM
    Subject: Re: Sextants with Polarizing filters
    
    
    >> Actually "ortho" means vertical thus 90 degrees to the horizontal plane
    >
    > Wow, Through the (polarized) Looking Glass
    >
    > http://photography.about.com/library/glossary/bldef_ortho.htm
    >
    > "Definition:
    >
    > Orthochromatic films were first produced by Hermann Vogel in 1873 by
    > adding
    > small amounts of certain aniline based dyes to ordinary photo emulsions,
    > work that was extended by others including J M Eder, who introduced the
    > use
    > of the red dye erythrosine in 1884.
    >
    > Early photographic materials were sensitive to blue light only, but ortho
    > materials extended this to green in the middle of the visible region.
    > Green
    > is also the colour our eyes are most sensitive to, so this greatly
    > improved
    > the tonal rendition of photographs. Ortho materials can be handled using
    > red
    > safelights, and are commonly used for special black and white films for
    > darkroom use - such as lith film."
    >
    > Off topic, but how does that "ortho" film relate to right angles?
    >
    > Alice?
    >
    >
    
    
    

       
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