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From: Courtney Thomas (no email)
Date: Mon Oct 06 2003 - 23:52:51 EDT
Doug,
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 CHO-M or a 1980
CHO-T. The CHO-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,
Courtney
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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