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Jean-Philippe,
I completely  agree with this:

> The only reserve I can express about the SNO-T is that it is
> finiky as far as the adjusting screws and bushes are concerned. One must
> be very cautious when adjusting the mirrors and study beforehand the
> system.

However, it keeps its adjustment very well. For years, I travel with it
2 times in an airplane, (in the luggage), by train, and 5-6 times by car,
probably 1000 miles total, and the
mirror parallism
does not need any adjustment. I adjusted it only once or twice
after I bought it.

Looking at the IC in my old records I see that it always was
about -0'3 (at least this is my best guess for it) since I bought it, and
I never adjusted it at all.

My only concern was when I sailed in a small boat, the sextant was
sprinkled with sea water almost every time I observed, I washed
the mirrors with fresh water (from my ration; water was scarce on board:-)
but I had no way to check that the salt water did not find its way
inside the worm cover (the worm is completely enclosed).
Bill Morris says that this is unlikely, unless you submerge it completely
in the water. Still it was somewhat disturbing that I cannot SEE the worm
and inspect it to make sure that it is clean.

Even greater problems I imagine will be encountered if one
uses it in a desert or in any voyage on land:-) Fine dust will certainly
penetrate any enclosure,
and there is no simple way to open it for cleaning in the filed.
Moreover, I afraid that dust may accumulate with years, even in
my appartment. And I am not a handy man, to open it with confidence
as Bill Morris does:-)

These considerations make me thing that sextants with open worm
are much simpler, and in many circumstances simplicity should be
preferred.

On land I usually travel with my pocket sextant, but I am considering
buying an SNO-M which looks more robust (but is less accurate,
documented!) for this purpose.

Alex.

   

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