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About two weeks ago, George H wrote:
"I've seen that sentiment expressed  before, by other seasoned professional
mariners, 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 thought this was an interesting post and intended to comment on it  but I
have only just now remembered it. Maybe some others will have some  thoughts. I
agree with your theoretical point, George, and so I've been trying  to think
what it is about an instrument with a little "heft" to it that makes it
easier to use. My best guess for now is that this is a feedback and control  issue.
The muscles of the hand and forearm may be able to control a somewhat
heavier sextant because of the feedback its inertia gives (more specifically,  its
moment of inertia). I think this also helps damp out hand tremors (which I
experience). Of course, at a certain point, the instrument would be too  heavy
for most people to hold comfortably so there should be some optimal  "middle"
weight. Just a thought...

Why don't people weigh down lightweight plastic sextants with lead  ballast?
Maybe for the very simple reason that no one thought of it before. It  might
very well be a good idea. Three little lead weights at the extreme corners
might give good stability without adding much weight.

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars

   

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