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    Re: Bubble horizon
    From: Paul Hirose
    Date: 2002 Dec 18, 13:20 -0800

    > The biggest drawback to the Kollsman is the reflective "pellicle" which is
    > situated inside of the body of the unit which transmits the image of the
    > celestial body to the eyepiece. Once it starts to absorb moisture it
    > wrinkles and spoils the view. For this reason, the Kollsman is fitted with a
    > removable cylinder which contains a desiccant to keep the pellicle dry and
    > taut. Every once in a while, you must remove this cylinder, dry out the
    > desiccant and replace it. Unfortunately for me, I left it for to long and
    > the pellicle self-destructed. I have not made much of an effort to find a
    > replacement so if you ever come across a supply of them, let me know.
    >
    
    Thanks for the warning regarding the dessicant. My Kollsman arrived
    this morning. Looks like it's in excellent condition. Paint is near
    mint, image is sharp, bubble size adjustable over a wide range,
    mechanical averager checks out fine. There are two dessicators. One is
    a tiny capsule visible through the window at the top of the optical
    tube. The other is in the sextant body. They're both turning pink, so
    I guess they ought to be filled with fresh crystals. The quantity is
    so small, it hardly seems worthwhile to bake the old dessicant in an
    oven. I need to research where to buy the stuff, though.
    
    When I was in the service we ordered dessicant by the gallon can. It
    was used to keep radar waveguides dry. New parts often arrived packed
    with little pillow bags of dessicant as well. They were usually
    discarded, but my boss saved them to keep humidity down in his gun
    cabinet.
    
    
    

       
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