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Fred,

The altitudes in question are recorded.
They are 37d, 36d, 35d and so on.
Which makes about 70 with the art horizon.
Not terribly high.

The same guy with the same sextant measured
good Lunars at 112d.

Prizmaticity of the art horizon is more plausible,
but his errors are much
scattered, both positive and negative.
Art horizon made of poor quality
window glass with bumps??

Alex.



On Fri, 27 Apr 2007, Fred Hebard wrote:

> This was in the tropics, was it not?  If he's getting latitude by
> noon observation, then the altitude of the sun is very high and the
> artificial horizon doubles the angle.  Not only do arc errors often
> increase dramatically at high angles, but it's much more difficult to
> even see the sun in the index mirror.  It's difficult to achieve
> conjunction of the bodies with an artificial horizon, more so than
> using a natural horizon.  I wonder why he didn't just walk down to
> the beach and use that, depending on it's orientation.
>
> Fred
>
> On Apr 27, 2007, at 5:26 PM, Ken Muldrew wrote:
>
> >
> > On 27 Apr 2007 at 10:59, Alexandre E Eremenko wrote:
> >
> >> But the errors in LATITUDE are enormous by comparison:
> >> 48', 6', 0', -1', 5', 5', 11', -2', -9', 0, -2', +4',
> >> This is not what I would expect from artificial
> >> horizon observations, even with a poor sextant.
> >> Even if we discard the 2 outliers (possibly some blunders)
> >> the average absolute error is 3.4' which is too large.
> >>
> >> Is it possible that some poor quality wood octant was used
> >> for the altitudes, and a metal sextant for the lunars?
> >
> > No, he clearly states that he only has the one, metal sextant with
> > him on
> > that trip. It may have been a problem with his artificial horizon
> > (non-
> > parallel glass, for example) or else he just missed the noon sight
> > due to
> > the demands of his party. I have no other explanation for why his
> > latitudes were so poor.
> >
> > Ken Muldrew.
> >
> > >
>
>
>
> >


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