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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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