POV-Ray : Newsgroups : povray.general : Accuracy of sunpos.inc for Prehistoric Dates Server Time
31 Jul 2024 16:25:09 EDT (-0400)
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From: kurtz le pirate
Subject: Re: Accuracy of sunpos.inc for Prehistoric Dates
Date: 7 Feb 2007 13:31:40
Message: <kurtzlepirate-94AB12.19314007022007@news.povray.org>
In article <45c9a603@news.povray.org>,
 Nicolas George <nicolas$george@salle-s.org> wrote:

> Well, all this is theory, and you probably can not do it with sunpos.inc.
> The first step can probably be done with ephemerides programs. As for the
> second, I have no idea.

all you say it's right and i think that povary can compute accurancy 
position of sun.

i begun to write a "small" macro for that and results are :


ephemeride values are :


all for the 1978, november 12, 0h ET.

as you can see, accurancy not bad. probably, increase precision with 
venus, jupiter moon and some others perturbations can be done.

 
-- 
klp


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From: Will S
Subject: Re: Accuracy of sunpos.inc for Prehistoric Dates
Date: 23 Apr 2007 10:30:02
Message: <web.462cc26192dd103d6b0a784b0@news.povray.org>
This issue also occurred to me after a visit this weekend - after all one
knows of considerable drift between supposed stellar alignments and the
more recent pyramids.

However - at the risk of being a naive non-expert I note that the
[date/]TIME of solstice does not matter in itself, only a drift in the
sun's maximum position = [defined by] the earth's rotational tilt wrt its
orbit, is material in judging the megalithic significance.  I would suppose
that this would only be subject to some (?roughly linear) tidal drift, and
even this must be rather small. Precession of a solid earth for example
would affect the time but not the angular excursion.  Of course the Earth
is not solid and I suppose this might also be important...

I also note the rather alarming comments in the wiki entry for newgrange
that the passage was 'straightened' during the controversial restoration a
few decades ago (though the current guides suggest that the interior is
untouched).


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