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From: Alexandre E Eremenko (no email)
Date: Tue Apr 25 2006 - 10:43:01 EDT
Dear George,
>Any error due to wear on the worm would be expected to repeat at
>one-degree intervals, so could affect readings close
Sounds very convincing!
So it is the arc. Or...the arm pivot.
> Why not really misadjust the index mirror, in a big way,
> Ideally, one might wish to shift the zero by
> perhaps two and a half degrees, to use an
While I am experimenting, I found the following alternative.
Instead of determining my IC
by the usual procedure, using one star,
I use TWO stars at a small distance.
Yesterday I used Castor-Pollux distance for this purpose,
which is 4d 30'.3
(Nautical almanac does not have Castor;
I had to use ISNO Astronomical almanach to compute this).
I will post the details in a separate message,
but from this Castor-Pollux procedure I found the index
correction -0'.7. Such correction would make my all
other star distances taken in the last week almost perfect!
> It's a potential problem, that the older,
> Vernier sextants didn't suffer from.
> Another disadvantage of progress, perhaps?
I also think so. And I hope my next sextant will be
one of those old ones with Vernier and microscope
and no teeth to worry about! If I find a good one.
Alex.
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