Actually, Paul de Kort may not be wrong at all, depending somewhat on your point-of-view. There are actually three definitions of the zodiac:
1. The zodiac definition that is most familiar to us is the "tropical zodiac", which ties Aries 0 deg to the vernal equinox and divides the tropical year into 12, 30 deg sections. This usage was probably introduced into Greek astronomy by Euctemon in the 5th century BC and was solidified by Ptolemy in his catalog of stars. The tropical zodiac has been used as a simple way to define ecliptic longitudes for 2,500 years.
2. The "sidereal zodiac" is older than the tropical zodiac. This definition also divides the year into 12 sections, but the divisions are defined by the position of Aldebaren at Taurus 15 and Anatares at Scorpio 0 (which is slighly in error - 1 arc min). Thus, the sidereal zodiac moves with stellar precession. The only use I know of for the sidereal zodiac is Hindu astrology.
3. The "astronomical zodiac" is defined by the boundaries of the constellations that lie on the ecliptic based on the constellation definitions adopted by the IAU in the 1920's. This set of constellations includes Ophiucus. I do not recall ever hearing of the constellations in the astronomical zodiac being called "signs", but the sun is, indeed, in Ophiucus in early December.
Happy Holidays,
Jim
James E. Morrison
janus.astrol...@verizon.net
Astrolabe web site at http://astrolabes.org
------------ Forwarded message ------------
From: Willy Leenders <willy.leend...@pandora.be>
Date: Dec 23, 2009
Subject: Re: zodiac lengths
To: Analemma zonnewijzers <i...@analemma.nl>
Hi Hendrik,
When he involves the sciences astronomy and astrology in his work he hits the wrong ball, however.
A sundial is primarily a scientific instrument. The zodiac is a scientifically determined reference system.
A "constellation of the zodiac" is a nonexistent concept. A "constellation of stars" exists. A "zodiac sign" exist too. He (and you) confuses the two.
And therefore, what he wrote in the brochure about the park in the suburb Saendelft in Zaanstad, is nonsense.
He wrote:
"In several thousand years, the signs of the zodiac are shifted from the position of the Earth and the Sun
We also see that the sun is not exactly during one month in a given sign, such as astrology says, deluding us.
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Paul de Kort is a good artist and he makes exceptional artworks and design.
When he involves the sciences astronomy and astrology in his work he hits the wrong ball, however.
A sundial is primarily a scientific instrument. The zodiac is a scientifically determined reference system.
A "constellation of the zodiac" is a nonexistent concept. A "constellation of stars" exists. A "zodiac sign" exist too. He (and you) confuses the two.
And therefore, what he wrote in the brochure about the park in the suburb Saendelft in Zaanstad, is nonsense.
He wrote:
"In several thousand years, the signs of the zodiac are shifted from the position of the Earth and the Sun
We also see that the sun is not exactly during one month in a given sign, such as astrology says, deluding us.
This varies from sign to sign and a few days to almost one and a half month.
And when you are born in early December, you are born under the sign of Ophiuchus, the 13th sign! "
Astrology and astronomy doesn't have differences in their definition of ecliptic and Vernal Equinox or the location of constellations, zodiac signs, sun, moon and planets in the ecliptic.
It is a big misconception that astrologers place their reference system in the stars and do'nt take account of the precession.
In the reference system of astrologers the precession is not useful. Stars and constellations do'nt have a place in it.
And when you are born in early December, you are born under the sign of Ophiuchus, the 13th sign! "
Astrology and astronomy doesn't have differences in their definition of ecliptic and Vernal Equinox or the location of constellations, zodiac signs, sun, moon and planets in the ecliptic.
It is a big misconception that astrologers place their reference system in the stars and do'nt take account of the precession.
In the reference system of astrologers the precession is not useful. Stars and constellations do'nt have a place in it.
Even if there were no stars the astrology would still have its reference system.
It consists of a system of positioning in the the ecliptic, starting from the vernal equinox, divided into 12 equal parts. In this system the position of the sun, moon and planets are projected, as seen from the Earth.
Their place in the ecliptic (at a given time, the birth a person for example) and how they interrelate (opposite each other, overlapping, in angles of 150, 120, 90, 60 and 30 degrees) is the underlying pattern that astrologers use.
It consists of a system of positioning in the the ecliptic, starting from the vernal equinox, divided into 12 equal parts. In this system the position of the sun, moon and planets are projected, as seen from the Earth.
Their place in the ecliptic (at a given time, the birth a person for example) and how they interrelate (opposite each other, overlapping, in angles of 150, 120, 90, 60 and 30 degrees) is the underlying pattern that astrologers use.
I simplify here, not talking about the Ascendant.
I am not talking about the statements by astrologers based on this reference system.
That is because it is outside the domain of astronomy.
That is because it is outside the domain of astronomy.
Willy LEENDERS
Hasselt in Flanders (Belgium)
Visit my website on the sundials in the province of Limburg in Flanders (Belgium) and on worthwhile facts about sundials
Op 23-dec-2009, om 8:45 heeft Analemma zonnewijzers het volgende geschreven:
Hi All,This reminds me of a sundial, made by Landscape artist Paul de Kort in Zaanstad/The Netherlands. For dialing usually the zodiac-signs are defined as 30 degrees of the ecliptica. However, the true sun will pass the 12 constellations of the zodiac and also the constellation Ophiuchus (dutch: 'slangedrager'). Paul did make a sundial in which this 13th 'zodiac'-constellation is incorporated. Very nice.for more work of Paul see: www.pauldekort.nlfor the sundial, see (page 6): http://www.pauldekort.nl/_backgrounds/getijdenpark%20BROCHURE%20lowres.pdfkind regards,Hendrik Hollander--------------------------
Analemma zonnewijzers
Hendrik Hollander
tel: 020 637 43 83
mob: 06 16 462 879
www.analemma.nl
www.linkedin.com/in/hendrikhollander
--------------------------
lees de disclaimer:
www.analemma.nl/maildisclaimer.htm
------------------------------- Original Message -----From: "Bill Gottesman" <billgottes...@comcast.net>To: <sundial@uni-koeln.de>Sent: Tuesday, December 22, 2009 4:51 PMSubject: Re: zodiac lengthsWell done, Frank!
-Bill Gottesman
Frank King wrote:
> Dear Thomas,
>
> You ask interesting questions and the
> answers depend slightly on just how
> precisely you want the model the way
> the sun goes round the ecliptic.
>
> QUESTION 1
>
> ... do [Gemini and Cancer] share
> *exactly* the same region [on a
> sundial] or not?
>
> I think it is reasonable to DEFINE
> the 12 regions of the Zodiac as being
> bounded at 30-degree intervals of
> solar *longitude*. So Aries extends
> from 0 to 30 and so on.
>
> On the ecliptic, these 12 regions are
> distinct and there is no sharing.
>
> When you look at the corresponding
> intervals of solar *declination*
> you do, as you say, get sharing.
>
> In your example:
>
> Sign Longitude Declination
> range range
>
> Gemini 60 to 90 20.15 to 23.44
>
> Cancer 90 to 120 23.44 to 20.15
>
> As you see, Gemini and Cancer share the
> same range of declinations but for Gemini
> the declination is increasing and for
> Cancer is decreasing.
>
> The answer to your question is YES.
>
> So far, this theory has nothing to do with
> the *shape* of the Earth's orbit but it does
> assume that the orbit is a plane which is
> isn't exactly.
>
> [Solar latitude hovers around zero but it
> isn't exactly zero. A REALLY pedantic
> discussion about whether Gemini and Cancer
> exactly overlap would take a book!]
>
> You then ask about dates. That makes the
> story very much more complicated but it
> doesn't stop Gemini and Cancer sharing
> the same region on a sundial.
>
> QUESTION 2
>
> Is the starting date May 20 of one in line
> with the end-date July 22 of the other or not?
>
> You go too fast. Who says the starting date
> is May 20? It sometimes is and it sometimes
> isn't. You have to worry about the leap-year
> cycle and Pope Gregory XIII and his friends.
>
> At the moment we are living close to the middle
> of an almost 200-year run of pure Julian
> calendar. There are no omitted leap-years
> between 1904 and 2096 inclusive. This means
> there is a steady drift in all the dates you
> are interested in.
>
> The starting *declination* of one IS in line
> with the ending *declination* of the other but
> when you worry about dates everything becomes
> harder.
>
> The only sensible answer to this second
> question is NO. It is no because the dates
> change from year to year. See the answer
> to Question 4, but first...
>
> QUESTION 3
>
> The angles of the ecliptic longitude for
> the zodiacs are equally distributed (each 30°),
> [YES that's right] but what about the angles
> in the earth's orbit around the sun (ellipse)?
>
> I don't quite understand this. The ecliptic
> longitude is the same as the angle of the Earth's
> orbit round the sun (though you might want to
> change the sign or add 180 degrees).
>
> The answer is THEY ARE THE SAME.
>
> QUESTION 4
>
> And what about the dates?
>
> They are horrible! I have already said there is
> a steady drift in the dates but it is worse than
> that because of the precession of the equinoxes.
> The answer is THE DATES ARE A MESS and...
>
> QUESTION 5
>
> The lengths (in terms of time) of the zodiacs
> are not equal, but are they constant each year?
>
> The answer is UNFORTUNATELY NO. It is easy to
> see that they are not constant by thinking about
> this time of year. We have just entered the
> sign of Capricorn and at this time of year the
> Earth is closest to the sun.
>
> That's good news because it gets winter over
> quicker. Capricorn doesn't last long! Also,
> this explains why the lengths are not constant.
>
> Unfortunately, there will come a time when we
> are furthest from the sun in winter. Capricorn
> will take longer and we could find the northern
> hemisphere covered in ice.
>
> [ There will then be conferences about trying to
> raise the levels of carbon dioxide :-) ]
>
> QUESTION 6
>
> Can anybody give me a better reference than
> Wikipedia...
>
> The best thing you can do is to ask your girlfriend
> to buy you a copy of "Astronomical Algorithms" by
> Jean Meeus as a Christmas present. You can then
> write a proper program to model the Earth-Sun
> system. It took me about 2000 lines of code before
> I was happy with it but it is a very good way of
> answering your questions!
>
> Best wishes
>
> Frank
>
>
> ---------------------------------------------------
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
>
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