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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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