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At 10:56 19/09/2005, Willem Piccer wrote, about the weight of an observing
instrument-:

>Weight is something which plays a minor role in the discussions we see here
>about the plastic sextant but to me it is important.
>
>If you use your sextant on a platform which is not stable than a sextant
>which has a certain weight will help you to obtain a more accurate
>observation because it is more stable.
>I know there is a sextant from John Bird ( around 1770) which has a "stick"
>on the backside to make it more stable.
>
>I suppose there is an optimum weight for a sextant : on one side not too
>heavy to handle and on the other side heavy enough to obtain a good
>observation.
>I remember when we started to use these light East German sextants that this
>was exactly  what was noticed: easy to lift but more difficult to make a
>good observation

=======================

I've seen that sentiment expressed before, by other seasoned professional
mariuners, and I would like to understand the basis for it. Why should a
heavy sextant be more stable, I ask (as someone who only ever owned a
plastic sextant, but has used others)? I respect the views of those who
have much more experience than I do, but remain as yet unconvinced.

After all, the windage on a sextant is just the same, when made of a light
material or a heavy one, if they are the same shape and size. If a sextant
is physically smaller, as some yachtsman's models are,  then wind forces
will be less. True, a heavy sextant will have more inertia, so it resists
initial movement, but when moving with the ship's roll, then it acquires
extra momentum, which makes it harder to bring it to a stop.

Sextant makers all seem to go to a lot of trouble to skeletonize the frames
of their instruments. If there was as advantage in having a heavier
instrument, why would they bother to do so?

The clinching argument, to my mind, against Willem's view, is that if
weight was a real advantage, mariners would "improve" their lightweight
instruments by simply adding lead ballast, to make the thing more "stable".
I have never heard of this being done, to any sextant, though it would be
easy to do in practice. Why not, then, if the extra weight would make it
somehow better? Convince me that it would.

=======================

I've missed recent Nav-L discussions, having been away on a family holiday
(four aboard) on a hired motor-cruiser on the River Charente, in south-west
France. For me, a real change, in that the only navigational decision was
whether to set off upstream and return downstream, or vice versa. It made
for a good holiday, but reinforced my preference for salt water, and sails.

George.
===============================================================
Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222,
or from within UK 01865 820222.
Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13
5HX, UK.

   

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