NavList:

On worn (or poorly manufacture red) sextants there is a possibility that
a reading taken by bringing the body up will be slightly different than
one taken by bringing the body down.

The real rule is not to take sights in just one direction, but to take
all sights in the SAME direction as you used in determining Index Error.

Lu Abel

Greg R. wrote:
> Sort of an off-the-wall question that occurred to me this past weekend
> while doing practice sights... I've read (and always practiced) that
> because of possible mechanical backlash in the micrometer screw
> mechanism you should do your final altitude adjustment in the same
> direction (i.e. either bringing the body up or down, not back and forth).
> 
> But wouldn't any backlash (i.e. any lag in the body moving up or down
> when turning the micrometer dial in the opposite direction) be
> immediately apparent to the person taking the sight? Both of mine seem
> to start moving immediately when I do that, but maybe there really is
> some subtle lost motion happening there that isn't obvious to the observer?
> 
> I'll try to remember next time I'm out at the beach to take a series of
> sights using both methods (racking in one direction vs. up and down to
> find the horizon "kiss") and see what the results look like.
> 
> --
> GregR
>
> >

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