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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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