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George-
 > Red can call it what he wishes. He seems determined to pick an
> argument, where none really exists.
 Relying on the semantics of "need" vs. "want" seems a tad extreme when the
topic are sextants, which today are solely a "want" as there is no "need" for
them in general. Surely, none of us "needs" a sextant, or anything to do with
it. I merely said that one prestigious maker seems to think this (index error)
is something their customers may want to zero on the instrument, regardless of
whether you think that is superfluous or unnecessary. As sextants themselves are
today.

> If Red distrusts his own arithmetic,...
 I distrust all arithmetic. It has been found that arithmetic leads to
arithmetical errors, and one reason that we have books of tables is because
navigators tend to make arithmetical errors when forced o "just do the math" all
the way by themselves. I am not too proud to say that I make math errors, I
sometimes get confused (especially in rough weather belowdecks at sea) and I
welcome any tool or process which will *eliminate* a potential source of errors.
That's what navigation is about. No simply having pride in your own success, but
ensuring that your entire process is as robust and error-free a possible.
 If you prefer to rely on your arithmetic prowess instead of "gimmicks" then
please, begin by burning your copies of all "tables" that were developed as
gimmicks to obviate arithmetic errors. Stand by your principles!

> On a slightly different matter, something else Red has said worries me
> somewhat.
 You should be worried, you are imaging things I haven't said.

> He wrote-|
> | While you've got a sextant in your hands for the first time, and
> presumably you
> | are taking the time to check it for errors and adjust them out...

> Well, that might be a reasonable attitude if a sextant arrives
> secondhand, with an unknown history from another owner. But I get the
> picture, rightly or wrongly, that if a sextant arrives new from its
> maker, properly packed in its undamaged box, Red is itching to get out
> the adjusting tool and tweak whatever he can get at.

And that's your own imagination. You have no reason for such an assumption.
Further, EVEN IF THE SEXTANT WAS BRAND NEW, you would be a poor excuse for a
navigator if you rashly assumed that it has arrived intact, with no shipping
damage, and retained the manufacturer's calibration. I am sure that I am not the
only list member who has found that even the "best" sources sometimes employ
workmen who have an off day. Sometimes a workman goes home at the end of the
day, is hit by a truck, and someone else takes over two days later, with the
result that an assembly process gets skipped during the hand-off.

Even closer to our hearts, would be the delivery of a new sailboat. Regardless
of the prestige of the builder, you would be rightly called a fool if you took
it transatlantic without first performing a shakedown cruise and an initial
survey. One does not rely blindly on the performance of unknown strangers when
one picks up their work product. Not in this day and age.

 >Such an
> instrument has presumably been adjusted at the factory, at least as
> well as it ever will be thereafter.

And, if you have ever seen shippers loading a delivery truck, you will know that
one never relies on a precision instrument which has been "shipped". That's why
they are all insured, and sometimes replaced. If you think the mirrors on a
sextant mightn't shift during five thousand miles in transit, by all means,
don't check them.


> Red is perfectly welcome to tweak it as he wishes; it's his sextant,
> after all. A better policy, in such circumstances with a new
> instrument, might be to carefully check over all the relevant points
> (perpendicularity, side error, collimation), but most users would then
> be better advised to keep their hands off the adjustments, unless a
> serious error shows up. And if it does, in those circumstances, I
> would expect the maker to want to know about it.
  You sound like you expect the average user to be a cobbler. And you would have
no reason to know my background and mechanical skills, which involve working to
what some would call crude precision, but others would call extreme precision. A
sextant is built to be robust, but it is also built to be maintained by the
ships' crew, far out at sea. Given a simple set of the proper tools, which
admittedly won't be found in the black gang's quarters, there is nothing to stop
a user from adjusting anything on a sextant. Whatever they can get out of whack,
can be adjusted back into whack.

Don't teach people to fear their machines and worship a cult of mechanic
priests, teach people the care and routine maintance the machines need. And in
the case of a sextant, I never have said it should be "adjusted" routinely. I've
never expressed an urge or need to do that. On the other hand, I do *check* it
routinely. I obtained mine both second-hand (or multi-hand) courtesy of
commercial shippers. Both could have worked "as is" but after two rounds
(iterative) of gentle attention, I was able to get the C&P down to a 0.6 mile
position and a routine position of some 2nm, which I felt were as good as the
sextant would ever get. I've continued to *check* it, but it has not needed any
adjusting since that first round. Accordingly, I haven't done any.

Your assumptions are totally off base.

>I would be rather careful, about
> any instrument that has been in his possession.

It is often said that when we make assumptions we make ASSes of ourselves. You
seem to go rather further, into being either a spiteful or malevolent assumer.
That's totally uncalled for, and only belittles yourself.

   

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