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    Re: SNO-T/CHO-M + Freiberger info
    From: Courtney Thomas
    Date: 2003 Oct 6, 22:52 -0500

    Thanks so much for the fulsome reply.
    Are you familiar with The Sextant Handbook ? In it there are tests that
    a typical user can carry out on his sextant  for collimation and index
    error. Just wonderin' how adequate they are.
    I assumed when I bought my Russian sextant(s) that, considering what was
    at stake, surely the Russian Navy powers that were, would have seen to
    it that their ships had, at least, good..... sextants. I must say I am
    much encouraged by your experience and observations.
    Which would you prefer [and why]; a calibrated, with manufacturer's
    certification [including non-adjustable errors] 1970 SNO-M or a 1980
    SNO-T. The SNO-T has a label in the box lid with a sequence of Russian
    data. But, I don't know if it applies to my sextant. i.e. this might not
    be the original box  for this sextant. But, no non-adjustable error data.
    What is the distinction between SNO and CHO ?
    Most appreciatively,
    Royer, Doug wrote:
    >Courtney,welcome to the list.Here is what I know.
    >I had the opportunity to use both of these types of Russian(I should say
    >Soviet)sextants.One was owned by a Polish ABS I served with and he
    >consistantly got outstanding LOPs useing his.He won an $1800.00 pool on one
    >transit when his final position was less than 0.2nm from the ships GPS pos.
    >when the evolution was stopped by the master.
    >Both of these sextants types were manufactured I beleive in Riga,Latvia and
    >someplace in East Germany between 1947 to 1988.They were built for the
    >Soviet Navy to rigorous standards.They are clones taken from the Freiberger
    >Prazisionmechanik Co.The optics in the scopes were Zeiss optics.And as all
    >Freiberger sextants are of the Drum type.Very good quality machining,
    >optics, very dependable and easy to use.The Index mirror is standard size
    >about 52 mm and I think also the silvering is on the front face of the
    >mirror.You will need to use cal. cylinders,dice or dominoes to check
    >perpendicularity of the Index mirror if that is the case.
    >The sextants I used were built in the ' 70's or early ' 80's.I can't say if
    >there were instrument cal. sheets for these on the lids of the boxes because
    >I can't remember.
    >All Freiberger sextants(man.after 1975)come with a cert certifying they are
    >free of Instument Error for practical purposes as do most sextants
    >manufactured today.These Russian sextants are clones of German
    >Equipement.Cassens + Plath and Carl Plath sextants have a max. error spec of
    >9" of arc over the arc's entire radius.Freiberger is right in there also so
    >your Rissian sextant should be the same.I would be more concerned about
    >Collumation Error and Index Error  than Inst. Error.I wouldn't waste time
    >and money trying to have the arc calibrated.I had my MS-733 calibrated years
    >ago at a good chunk of change to find the whole error was 11" of arc.If you
    >want it collumated there are many places that will do that service for you.
    >The Clausen Inst. Co. is the importer for Freiberger sextants in the U.S.
    >and I am sure they have a website.If you need an owners manual maybe they
    >can help.
    >Hope this helps you out and good luck.
    Courtney Thomas
    s/v Mutiny
    lying Oriental, NC

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