Re: zodiac lengths

[Willy Leenders]

I believe you, Hendrik, but you will have to admit that the text in  
the brochure about the park in the suburb Saendelft in Zaanstad is  
very carelessly written.



Kind regards.

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

www.wijzerweb.be



Op 24-dec-2009, om 9:43 heeft Analemma zonnewijzers het volgende  
geschreven:



Hi Willy,

No worries, Paul and I are totally aware of the differences between  
"constellations of stars" and "zodiac signs". Also how the  
precession of the earth influences the position of the Vernal  
Equinox with respect to the contellations of stars and why my sign  
is Cancer since my birthday is the 1st of July, although the  
position of the sun is in the constellation Gemini.


Paul, as an artist, made an object which, among other things,  
enables people to start a discussion about these subjects and I  
think he has succeed very well!


kind 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
--


- Original Message -
From: Willy Leenders
To: i...@analemma.nl
Cc: Bill Gottesman ; sundial@uni-koeln.de ; Paul de Kort
Sent: Wednesday, December 23, 2009 1:23 PM
Subject: Re: zodiac lengths

Hi Hendrik,

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.
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.

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.

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

www.wijzerweb.be



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.nl

for the sundial, see (page 6):  http://www.pauldekort.nl/ 
_backgrounds/getijdenpark%20BROCHURE%20lowres.pdf


kind 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" 
To: 
Sent: Tuesday, December 22, 2009 4:51 PM
Subject: Re: zodiac lengt

Re: zodiac lengths

[Analemma zonnewijzers]

Hi Willy,

No worries, Paul and I are totally aware of the differences between 
"constellations of stars" and "zodiac signs". Also how the precession of the 
earth influences the position of the Vernal Equinox with respect to the 
contellations of stars and why my sign is Cancer since my birthday is the 1st 
of July, although the position of the sun is in the constellation Gemini.

Paul, as an artist, made an object which, among other things, enables people to 
start a discussion about these subjects and I think he has succeed very well!

kind 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
--

 

- Original Message - 
From: Willy Leenders 
To: i...@analemma.nl 
Cc: Bill Gottesman ; sundial@uni-koeln.de ; Paul de Kort 
Sent: Wednesday, December 23, 2009 1:23 PM
Subject: Re: zodiac lengths


Hi Hendrik,


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.
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.
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.


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
www.wijzerweb.be





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.nl

  for the sundial, see (page 6):  
http://www.pauldekort.nl/_backgrounds/getijdenpark%20BROCHURE%20lowres.pdf

  kind 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" 
  To: 
  Sent: Tuesday, December 22, 2009 4:51 PM
  Subject: Re: zodiac lengths


  Well 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 

Fwd: Re: zodiac lengths

[James E. Morrison]

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,JimJames E. Morrisonjanus.astrol...@verizon.netAstrolabe web site at http://astrolabes.org Forwarded message From: Willy Leenders Date: Dec 23, 2009Subject: Re: zodiac lengthsTo: Analemma zonnewijzers Hi Hendrik, 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.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.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.Willy LEENDERSHasselt in Flanders (Belgium)Visit my website on the sundials in the province of Limburg in Flanders (Belgium) and on worthwhile facts about sundialshttp://www.wijzerweb.be/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 zonnewijzersHendrik Hollandertel: 020 637 43 83mob: 06 16 462 879www.analemma.nlwww.linkedin.com/in/hendrikhollander--lees de disclaimer:www.analemma.nl/maildisclaimer.htm--- Original Message - From: "Bill Gottesman" To: Sent: Tuesday, December 22, 2009 4:51 PMSubject: Re: zodiac lengthsWell done, Frank!-Bill GottesmanFrank King

Re: zodiac lengths

[Willy Leenders]

Hi Hendrik,

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.
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.

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.

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

www.wijzerweb.be



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.nl

for the sundial, see (page 6):  http://www.pauldekort.nl/ 
_backgrounds/getijdenpark%20BROCHURE%20lowres.pdf


kind 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" 
To: 
Sent: Tuesday, December 22, 2009 4:51 PM
Subject: Re: zodiac lengths

Well 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
>
>   Gemini60 to 90 20.15 to 23.44
>
>   Cancer90 to 12023.44 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
> 

Re: zodiac lengths

[Analemma zonnewijzers]

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.nl

for the sundial, see (page 6):  
http://www.pauldekort.nl/_backgrounds/getijdenpark%20BROCHURE%20lowres.pdf

kind 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" 
To: 
Sent: Tuesday, December 22, 2009 4:51 PM
Subject: Re: zodiac lengths


Well 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
>
>   Gemini60 to 90 20.15 to 23.44
>
>   Cancer90 to 12023.44 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. 

Re: zodiac lengths

[Bill Gottesman]

Well 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
>
>   Gemini60 to 90 20.15 to 23.44
>
>   Cancer90 to 12023.44 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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Re: zodiac lengths

[Frank King]

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

  Gemini60 to 90 20.15 to 23.44

  Cancer90 to 12023.44 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


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zodiac lengths

[Thomas Steiner]

Hi,
a lot of sundials show the tweleve zodiac signs. Eg Gemini (♊) and
Cancer (♋) do share the same "region" on the sundial. My question is:
do they share *exactly* the same region or not? Is the starting date
May 20 of one in line with the end-date July 22 of the other or not?
The angles of the ecliptic longitude for the zodiacs are equally
distributed (each 30°), but what about the angles in the earth's orbit
around the sun (ellipse)? And what about the dates?
The lengths (in terms of time) of the zodiacs are not equal, but are
they constant each year?
Can anybody give me a better reference than
http://en.wikipedia.org/wiki/Zodiac#Table_of_dates or even improve
this table?
Thanks a lot,
thomas

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