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I am of the same opinion (as George and Red)
on this C-Plath gimmick: adjusting for the
index error. It saves you ONE arithmetic
operation in reducing the sight,
namely one addition/subtraction (of the Index error).

To Joel: is THIS the feature that makes C-Plath
Navistar Classic "the best sextant in the world"?
:-)

Alex.

On Sun, 14 May 2006, Red wrote:

>
> George, failing to use a zero-adjustment, after obtaining a sextant that was
> designed and built and sold at extra cost in order to enable you to make that
> adjustment, is certainly possible. You are right. And building one, at
> unnecessary expense which places your product at a marketing disadvantage, does
> not mean the user MUST use it. You're right again.
>
> But failing to use the device, which can and often will eliminate one potential
> source of math error from your reductions, makes absolutely no sense at all. It
> would be what I call "belligerent ignorance", taking pride in NOT obtaining or
> using the information and resources that in this case are literally at your
> fingertips.
>
> 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, you would have
> to be a particularly stubborn old coot to refuse to use one of the simplest and
> most obvious tools on it to remove one step from all subsequent observations.
>
> I expect those people wouldn't bother using a sextant at all, when they can
> simply look at their own feet and announce just as confidently "I am HERE!"
>
> ----- Original Message -----
> From: "George Huxtable" 
> To: 
> Sent: Sunday, May 14, 2006 1:34 PM
> Subject: Re: sextant calibration
>
>
> > Red appeared to argue with my earlier statement-
> >
> > | "But one adjustment that does NOT  EVER
> > | need to be made is the zeroing of index error, whatever it may be."
> >
> > in writing
> >
> > | The Plath companies apparently disagree with you, George. Their
> > sextants are
> > | built with an extra wheel and scale to allow the user to zero out
> > the index
> > | error. Would I do this every time? No, certainly not. But it is
> > something that a
> > | user certainly would do the first time they got the sextant, and
> > were trying to
> > | set up a baseline of adjustments on it, including the mirror
> > positions.
> > |
> > | More like, to quote Gilbert & Sullivan's Mikado, "Never? Well,
> > hardly ever!" 
> >
> > What I said was that the index error adjustment, to bring it to zero,
> > does not ever need to be made, and that's a correct statement. The
> > fact that Plath have arranged things so that if you want to adjust it,
> > it's easy to do so, does not invalidate what I said. That's not the
> > only instrument for which such provision has been made. I remember
> > seeing an ebony octant, from the early 1800s, provided with a
> > lever-on-lever mechanism for fine-tweaking the angle of the horizon
> > mirror, for just that purpose. It provided just the right sensitivity
> > of adjustment, and stayed nicely put when you let it be.
> >
> > But just because you CAN make such an adjustment doesn't mean you NEED
> > TO. When Red says it's something "a user would certainly do the first
> > time", I wonder where he gets that certainty from.
> >
> > George.
> >
> > contact George Huxtable at george@huxtable.u-net.com
> > or at +44 1865 820222 (from UK, 01865 820222)
> > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
> >
>

   

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