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    Re: on washing sextants
    From: Joel Jacobs
    Date: 2004 Aug 3, 08:24 -0400

    Peter,
    
    The most damage that befalls a sextant is due to living in a salt
    atmosphere, particularly when used from small craft where they are subject
    to frequent spray. Salt water, left unattended will first attack the
    mirrors. The backside of the mirror's frames have a trough which collects
    more of this spray then elsewhere and this starts to erode the silvering. In
    time, it also will eat into any chrome parts, cause the paint to bubble and
    lift on the frame. It will do major damage to a sextant with an aluminium
    frame as salt water is a strong electrolyte.
    
    The prevention is to rinse the sextant in fresh water after each use,
    whether its been subjected to salt spray or not. If the sextant has its
    tangent screw encased in a barrel or cylinder like the Russian and
    Freiberger sextants make sure to run a lot of water through it which will
    keep the screw from freezing. Then of course wipe down with a soft cloth.
    From time to time, you may also add some lubricating oil to the tangent
    screw for protection on those that are housed. This is not necessary on
    sextants with open screws. Doug Royer recommends NYOIL.  Jared Sherman
    recommends DuPont Krytox. I use what I have handy which is Vaseline and
    Never Seize. The latter only on a tangent screw encased inside a barrel or
    cylinder because it does stain.
    
    Doug some time ago wrote a message which went into great detail of how he
    and others on his ship took great pains to clean their instruments and
    protect them. One of his recommendations was the use of RainX on the
    mirrors. Hopefully he saved that message and can re-send.
    
    I also would like to hear what Jim Thompson has to say. He has one of the
    most comprehensive sites on the internet devoted to CELNAV.
    
    Joel Jacobs
    
    
    
    ----- Original Message -----
    From: "Peter Fogg" 
    To: 
    Sent: Monday, August 02, 2004 10:45 PM
    Subject: on washing sextants
    
    
    > Quoting Joel Jacobs
    > ..where I
    > > was talking about washing a sextant after use.
    >
    > Would Joel, or anyone else, like to go into a little detail about this
    sextant washing idea?
    
    
    

       
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