NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: first sextant sights
From: Alexandre Eremenko
Date: 2006 May 3, 11:43 -0500
Jim,
On Wed, 3 May 2006 jimattac@aol.com wrote:
> I have posted some results I have taken
> under excellent conditions
Where did you post these results?
> and found that the <0.5 claim not unreasonable and certainly
> not if an artificial horizon is used.
Well, of course, if the art horizon is used, one has
to multiply the error by two, when comparing with
ordinary shots.
> Obviously you simply are not going to get the
> same result with a single shot on the deck of
> a pitching sailboat.
Sure. These are the separate things, of different nature.
So I am trying to analyse them SEPARATELY.
a) small boat problems
b) horizon problems
c) reduction and almanac errors
and
d) sextant and observer acuracy in taking sites.
In discussing d) as a separate issue from a) and b) and c),
I am thinking of the observations of star-star and Lunar
distances on land under ideal conditions only. One can
add art horizon observations to the same category.
> Maybe with ideal conditions, lots of work on IE,
> averaging, graphing, good knowledge of instrument
> error and close attention to almanac data
> and reduction method you could but this would
> really be taxing the limits.
That's what I am trying to do.
> It is not founded on any analysis but,
> I do have to believe that top end modern
> sextants are better that what Cook
This is not evident to me.
I've seen the results of Cook's astronomers,
enough of them to judge about accuracy.
But I have seen very few modern results with best sextants
to compare. Maybe someone will post such results?
(I mean distances and art horizon from land).
Alex.
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From: Alexandre Eremenko
Date: 2006 May 3, 11:43 -0500
Jim,
On Wed, 3 May 2006 jimattac@aol.com wrote:
> I have posted some results I have taken
> under excellent conditions
Where did you post these results?
> and found that the <0.5 claim not unreasonable and certainly
> not if an artificial horizon is used.
Well, of course, if the art horizon is used, one has
to multiply the error by two, when comparing with
ordinary shots.
> Obviously you simply are not going to get the
> same result with a single shot on the deck of
> a pitching sailboat.
Sure. These are the separate things, of different nature.
So I am trying to analyse them SEPARATELY.
a) small boat problems
b) horizon problems
c) reduction and almanac errors
and
d) sextant and observer acuracy in taking sites.
In discussing d) as a separate issue from a) and b) and c),
I am thinking of the observations of star-star and Lunar
distances on land under ideal conditions only. One can
add art horizon observations to the same category.
> Maybe with ideal conditions, lots of work on IE,
> averaging, graphing, good knowledge of instrument
> error and close attention to almanac data
> and reduction method you could but this would
> really be taxing the limits.
That's what I am trying to do.
> It is not founded on any analysis but,
> I do have to believe that top end modern
> sextants are better that what Cook
This is not evident to me.
I've seen the results of Cook's astronomers,
enough of them to judge about accuracy.
But I have seen very few modern results with best sextants
to compare. Maybe someone will post such results?
(I mean distances and art horizon from land).
Alex.
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To unsubscribe from this group, send email to NavList-unsubscribe@fer3.com
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