Talk:Zodiac/Archive 2

Gaps in the sidereal dates
The list of sidereal zodiac dates has serious problems: there are gaps between the signs in the dates. Surely that is not correct; see the sidereal zodiac article. (is that one correct?)--66.243.235.236 (talk) 01:42, 11 June 2010 (UTC)
 * I just noticed this myself. Also, some of the dates differ with those given for this article.--Robbstrd (talk) 20:37, 12 July 2010 (UTC)


 * On 3 April 2009, Dbachmann changed the original pair of sidereal dates which were simply typed, such as 14 April – 14 May for sidereal Aries, to a pair of dates calculated via the template which is obviously flawed. Instead of adding 24 days to the last day of the tropical sign of Aries, 20 April, the template erroneously adds 24 days to the first day of the sidereal sign of Aries, 14 April, so sidereal Aries "ends" on 7 May instead of 14 May. Ditto for all other sidereal signs. The minor differences in dates are due to different editors and their differing criteria. — Joe Kress (talk) 03:07, 13 July 2010 (UTC)

The synagogue mosaic is terrible
What exactly are the merits of this mosaic? Artistically, this is worse than a 6-year-old could draw. Is it the most ancient picture of Zodiac Circle? I doubt it. I am upset just by looking at this art mockery. 85.65.137.175 (talk) 09:52, 4 October 2010 (UTC)

It isn't vandalism
The "13 zodiac signs" thing isn't vandalism. I started a discussion here a couple of hours ago. Whether it will become widely accepted remains to be seen (I don't know how that would even be decided) but the changes shouldn't be reverted as vandalism. Kafziel Complaint Department: Please take a number 00:40, 14 January 2011 (UTC)


 * As a lot of the back-and-forth appears to be coming from anonymous editors unfamiliar with our guidelines and our policy against edit warring, I have semi-protected the article for 24 hours. In the meantime, hopefully a consensus can be reached about how to proceed. Kafziel Complaint Department: Please take a number 01:31, 14 January 2011 (UTC)

Are the IAU dates from 1977? This ref is more recent; it's off by one day for all but one of the dates.

The zodiac has little to do with the stars, just as the months of our calendar have little to do with the moon. The houses are simply named after the constellations; it's divided evenly into 12 because the day and night are divided evenly into 12 hours. 8 pm isn't a shorter hour than 10 pm just because the corresponding constellation as defined by the IAU (or even by common sense) is narrower than the one for 10 pm. Saying you're an Ophiuchus rather than a Scorpio may be fun, but it makes no more sense than the IRS demanding your taxes by the full moon (= middle of the month). Circus horoscopes aren't going to change just because every few years some planetarium pokes holes in astrology as part of a public outreach program. — kwami (talk) 08:59, 14 January 2011 (UTC)

As always, the question is not "is it stupid", it is "is it notable". Of course it is stupid. But is it notable? This article is about a 26 century old tradition. The Ophicuus thing is what, 20 years old? Unless excellent references are shown that establish notability, I assume WP:UNDUE. --dab (𒁳) 12:35, 14 January 2011 (UTC)
 * It's been widely reported in dozens of reliable sources over the past two days. Correct or not, this time around the suggestion is clearly notable. Kafziel Complaint Department: Please take a number 15:46, 14 January 2011 (UTC)

Why not create a "the Opichus controversy" paragraph? If it's kept as a sidenote of something that happened, rather than pretending it never occurred, I'm sure the so-called vandalism will diminish. 159.90.10.250 (talk) 14:49, 14 January 2011 (UTC)

We do address it, and even have an article on it. — kwami (talk) 17:54, 14 January 2011 (UTC)

What "controversy"? Nobody disputes that the ecliptic passes across the IAU boundaries of Ophiuchus. It just doesn't have anything to do with this article's topic. If you suggest that a bunch of online newspaper headlines of the "past two days" has any relevance of a topic of Babylonian antiquity, Hellenistic astrology and Renaissance magic, you obviously have no clue about lazy journalism. --dab (𒁳) 18:03, 14 January 2011 (UTC)


 * This goes back at least to 1977, and probably further. — kwami (talk) 18:18, 14 January 2011 (UTC)
 * we need to distinguish between smart-ass astronomers trying to ridicule astrologers, and astrologers who were actually trying to reform the zodiac. Of course either can be discussed in the article, but make it WP:DUE, in a "20th century" section. --dab (𒁳) 19:47, 14 January 2011 (UTC)

Minnesota Planetarium Society
Seriously, we need writers to start discussing this nonsense on the Minnesota Planetarium Society article. This craziness needs to be nipped in the bud, by propagating clear information, the way only Wikipedia can. -- Zanimum (talk) 14:38, 14 January 2011 (UTC)
 * It's not just the MPS. Lots of planetariums do this from time to time, since people assume the zodiac corresponds to the constellations. — kwami (talk) 17:31, 14 January 2011 (UTC)
 * well it does. Or did. It then went on and shifted, but the original system of 600 BC was obviously directly tied to the constellations. --dab (𒁳) 18:03, 14 January 2011 (UTC)
 * I don't think the constellations were ever equidistant, were they? There would have had to have been major differences in which stars were included in 600 BC. — kwami (talk) 18:06, 14 January 2011 (UTC)
 * I don't think the constellations had well-defined boundaries in antiquity, and I don't think any but the most obvious stars were included in them. I actually think the zodiac constellations may originally have been pieced together so as to be as equidistant as possible. --dab (𒁳) 18:10, 14 January 2011 (UTC)
 * I'd be curious as to how equidistant they could be made to be. Taurus, Leo, Gemini, and Scorpio are all visually quite well defined; I doubt changing them at the margins would do all that much: they'd need to be moved. — kwami (talk) 18:13, 14 January 2011 (UTC)
 * we are talking ancient astronomy, not rocket science, I couple of degrees off doesn't do any harm. Here is what happened: in 1000 BC, Babylonian astronomers simply described the ecliptic by listing some stars (not necessarily constellations) along it. There were about 17 or 18. By 600 BC, the "Chaldeans" began to construct a lot of religious significance attached to astronomy, and for some reasons, they decided there must be twelve houses along the ecliptic. So they picked the twelve best suited stars (and their constellations) from the earlier lists. People saying there are really 13 miss the point entirely. There are any number of stars along the ecliptic, but the astrologers wanted to have twelve, so they picked twelve, out of a larger number they had already listed.  --dab (𒁳) 19:43, 14 January 2011 (UTC)
 * Don't they correspond to the 12 months? 'Course, there are 12½ months to a year, assuming they were still on a lunar calendar, so I'd be curious as to how that came about. Maybe s.t. divisible by 4 for the solstices & equinoxes. Yeah, close enough to 30* for the moon to be centered on a different constellation each month would work, and the solstices/equinoxes do line up, so maybe that was good enough. — kwami (talk) 10:05, 16 January 2011 (UTC)

Ophiuchus, again
I can not find any references to this astrological sign in any of the texts on astrology I have read. I consider this sign to be a hoax, there are only 12 signs in the zodiac.Nekochan1973 (talk) 19:28, 14 January 2011 (UTC)

it's not a hoax, it's just a silly recentism. "zomg the zodiac has been mentioned in the news, quick we must head over to Wikipedia and butcher the zodiac article". For crying out loud, we have discussed Ophiuchus at length, in 2006. It's even still on this page. To Jstuck21677, if your main source of knowledge on the topic is  google news perhaps you could consider using Wikipedia to learn something. You know, by reading it instead of disfiguring it with stupid edits. Also, more than a year ago, the Ophiuchus (astrology) artice has been created. If you must you can include your "reliable sources" there. --dab (𒁳) 19:40, 14 January 2011 (UTC)

Can people also condescend to use the talkpage instead of edit-warring? I will consider reverts that aren't explained in a coherent statement here on talk as subject to rollback. Read WP:BRD. You want to make a change to a long-standing, stable article? Do it. If you are reverted, don't do it again but seek consensus first. --dab (𒁳) 10:26, 15 January 2011 (UTC)

why here, why now?
I just found a 1974 astrological publication, Stephen Schmidt's Astrology 14 Horoscope, which proposed 14 signs of the zodiac, adding Ophiuchus and Cetus. But Schmidt's book was not widely read, and apparently is now forgotten even by astrologers, let alone journalists. The reason we are talking about this is, I presume, the introduction of the Unicode 6.0 standard in October 2010. Mr. Kunkle must have scanned the new characters, and noted the "Ophiuchus symbol" introduced at U+26CE. At least I cannot imagine there is no connection between the introduction of this symbol, and the online hysteria about a 13th sign of the zodiac erupting two months later. Why did the Unicode Consortium introduce an Ophiuchus symbol? Because Ophiuchus as an astrological sign has been popular in Japan, the home of everything that is weird and different, for more than ten years. Why has it become popular in Japan? God knows, but it started with Walter Berg's book The 13 Signs of the Zodiac becoming a bestseller in Japan in 1996.

What really disheartens me the most is that NBC, where this thing apparently originated, reports the precession of the equinoxes as "news", and confronts "members of the US public" with this revelation, who react to this "discovery" with surprise. Who knew, indeed.

This is something that has been known to all astronomers, and all astrologers, for 2,100 years. It has been known to anyone with half an education for at least 100 years. If there is anything to learn here, it is the complete lack of education of the general population in North America, and the failure to at least google and glance at Wikipedia where these things can be read up for free on the part of the popular media. And sadly enough it isn't just a case of "Americans are dumb", I think they are just least embarrassed to show that they are. Of course it wasn't below German media to repeat the headline. I a depressed now. --dab (𒁳) 11:08, 15 January 2011 (UTC)
 * Ah, yes. If only Americans knew more about the zodiac, we could have as good a space program as Germany does. Maybe someday we could even put a man on the moon.
 * This anti-American rhetoric doesn't help the discussion, and as an admin you should know better. This article is about mythology and superstition, neither of which is encouraged in the scientific curriculum in the United States or in any other developed country I know of. Perhaps you were looking for Ecliptic coordinate system and wound up at Zodiac by mistake? It's the only explanation I can think of as to why you seem to think schoolchildren should be taught about the history of Babylonian astrology and men wrestling snakes. Kafziel Complaint Department: Please take a number 09:31, 16 January 2011 (UTC)
 * Perhaps you could read everything he said? It was hardly anti-American. — kwami (talk) 09:52, 16 January 2011 (UTC)
 * "If there is anything to learn here, it is the complete lack of education of the general population in North America." In what way is it not? Maybe you should re-read it. Kafziel Complaint Department: Please take a number 16:11, 16 January 2011 (UTC)

CONSENSUS ATTEMPT at Zodiac sign
see here.

This article is in good shape so why not continue the consensus from here to the Zodiac sign article? Alatari (talk) 22:01, 4 February 2011 (UTC)

Rumors of changes
Hey guys, a lot of my friends have recently been talking about changes in the zodiac system. Something about our planet does circulate around the sun in a different way than we had thought for years and that will change some of the dates in the zodiac system and also I've heard rumors that a "snake" have been added. Just wanna be sure if those rumors are true? -Jalokin95 (talk) 13:51, 16 January 2011 (UTC)

See right above your comment - "Opiuchus, again?". That's what I came here to read about, and the short answer is no, they are not true 80.7.86.234 (talk) 18:34, 16 January 2011 (UTC)

I'm sorry, but I think a few people editing this page are far too close to the subject matter and aren't giving the general public what it wants. Most people don't pay a great deal of attention to the zodiac, so when we see a flurry of news reports about a 13th sign, we want to know about it. And we want to check it out on Wikipedia. Greeting those people with a general zodiac page that doesn't address the question, then dismissing those people on the talk page ... I'm sorry, but that's not what Wikipedia is all about. Can someone please sum up the "13th sign" question? Bdure (talk) 21:22, 15 February 2011 (UTC)


 * Bdure, the facts are these. The zodiac is an artifice, the babylonians and persians used a mix of constellational astrology and evolved it into an 'idealised' notion of an equal circle divided into 12 by about 500BC. They were, undoubtedly, aware of Ophiuchus which is the suspected 13th sign. They did not utilise it. Precession of the equinoxes is a phenomenon whereby the apparent fixed stars (constellations) actually move ever so slightly from their locations from one year to the next. It's tiny, only 1 degree every 72 years. However it's enough that by now, the original constellation that was in the background on the spring equinox has moved by almost a whole sign. As a result we have two zodiacs, the sidereal and the tropical. The sidereal uses the beginning of the constellation Aries which was the constellation the sun was seen at at the time of the spring equinox in around 500-200BC. Then we have the tropical zodiac, which is claimed to evolve from the former such the babylonians began evolving from literal constellations to idealised divisions of a circle. The tropical zodiac states that whatever 'point' of space is found at the moment of the spring equinox, in other words, the precise intersection of the celestial equator with the eclipitc, is the beginning of the SIGN aries (not the constellation of the same name). So signs are not constellations. The problem is in the apparent misunderstanding of this with certain astronomers. They recognise that what was once the spring equinox occurring in the constellation of Aries, now occurs in the constellation of Pisces. However they do not seem to understand that western astrology uses signs based upon idealised divisions of the ecliptic from the spring equinox, and do not use constellations whatsoever. Hence they assert that our current signs are off, in truth the constellations are off from where they were, but western astrology does not employ constellations (though it once evolved from it millennia ago) so it's irrelevant. In addition, they point out that another constellation (remember how they're irrelevant?) intercepts the ecliptic, it is called Ophiuchus, and they suggest it is a 13th sign. However, as is evident now, constellations are irrelevant so there are no new signs. In truth the babylonians were likely aware of Ophiuchus, certainly we know that Hipparchus in the 2nd century BC was aware of precession and was an astrologer, also that Ptolemy in the 2nd century AD was an astrologer and also was aware of both Ophiuchus and precession, as he explicitly mentions both, and yet still continued to use a tropical (constellationally irrelevant) zodiac and was a recognised master physicist and mathematician of his time. Hope this helps shed some light on the situation. In conclusion the astronomers seem to misunderstand how the astrological zodiac is actually calculated. In my view, deliberately. Astrologers have been aware of all this for at least 2000 years, almost certainly longer. There is nothing new here, save for a cheap sensationalist headline perhaps. Xpaulk (talk) 20:52, 18 February 2011 (UTC)


 * The problem stems from people thinking that astrology has s.t. to do with the stars: "reading the stars", "foretold by the stars", etc. Thus they assume that constellations have a present connection with signs. I agree with Bdure that we should mention the '13th constellation' in the lede and either link to it or clarify it. What you just wrote, Xpaulk, would be perfect. — kwami (talk) 23:06, 18 February 2011 (UTC)


 * I agree. Plenty of people come to Wikipedia to see if what they're hearing is accurate. If you can explain that it's not, great. Those of us who don't know the past 2,000 years of the history of astrology and come here to learn what they can would greatly appreciate it. To give another example - Wikipedia has a compete entry on the infamous "Dewey Defeats Truman" headline. The headline is also mentioned in the Harry Truman entry, the 1948 presidential election entry and the Thomas Dewey entry. It's part of the folklore, and the entries would be less complete without it. 64.134.67.163 (talk) 15:45, 24 February 2011 (UTC)

Zodiac sign
Since the side-real and tropical signs are the same it would be easy for any common user to come in here and try and find some information on this '13th sign media event' in the Zodiac sign page only to be greeted with the tropical only dates and no Ophicus(sp) explanation/denial/rebuttal. To deflect edit warring I would suggest the chart and some of the explanation from the Zodiac article be migrated into the sign page. The arguments that lead to the excellent layout of the Zodiac page would seem to apply here also. Alatari (talk) 17:02, 4 February 2011 (UTC)

Newbie here :-) with finger on Oph pulse for going on 25 years; familiar with issues, history, etc.; makes this suggestion: for clarity, the "symbol" assigned to Ophiuchus on the Zodiac page should be removed. Here are the reasons: (1) Symbol use gives the impression that Oph is a zodiac "sign".  (2) As far as I am aware, no symbol has officially been decided upon by those who are working with the Oph energy in the context of Astrology.  (I am curious, just for my own information, who came up with this symbol and what it represents to him/her/them.)  Thank you.  Donnajpro (talk) 00:41, 12 March 2011 (UTC)

Why is Ophiuchus still here?
Seven mentions of Ophiuchus seems excessive for a constellation that was never part of the Zodiac. If inclusion is based on the artificial IAU boundaries crossing the ecliptic, this literal interpretation should also mention the constellations of Orion and Cetus since their boundaries fall well within the 9° band either side of the ecliptic. And why are we promoting Walter Berg's 13 sign book (here and elsewhere on WP)? Far from being a pioneer as suggested, the small paperback was rushed out to take advantage on the first Press 'sensational' discovery of the misnomered "13 signs" in 1995. It all started as a publicity stunt by astronomer, Jacqueline Mitton to promote a BBC TV astronomy series. She was as surprised as anyone at how credible journalists fell for this 'news' just as they did in the USA in January 2011. An explanation is necessary here but putting it into tables with dates is misleading and duplicating the information into two sections: zodiacal constellations and modern astronomy is totally unnecessary.

In 1983, Stern magazine published the 'scoop of the decade' - the Hitler Diaries. People need to know it was a hoax, but it should not predominate pages on the life of Hitler. Robert Currey  talk  23:06, 12 July 2011 (UTC) Note: I edited heading to avoid conflict with previous Ophiuchus heading. Robert Currey  talk  08:12, 13 July 2011 (UTC)
 * Ophiuchus (constellation) belongs to the Table of dates, while Ophiuchus (astrology) is being considered for deletion. Readers would like to see a comparison of the dates of tropical, sidereal and IUA. I believe that Walter Berg is too uncommon and should be removed. --Regards, Necessary Evil (talk) 23:56, 12 July 2011 (UTC)


 * Thanks Necessary Evil, IMO re-editing of Ophiuchus (astrology) is better than deletion as it is a controversy and the background needs to be explained in full. I don't think this Zodiac page is the place to showcase a pseudo-zodiac sign: Ophiuchus - a single mention and link is sufficient.  I agree that it is certainly not the page to promote a minor book about it.


 * I understand that the date table is of interest and quite appealing. However, I feel it is misleading in several ways:
 * First the Tropical data links #17 to a site that is full of advertising http://my.horoscope.com/astrology/horoscope-sign-index.html rather than content. Many of the dates listed on this commercial site are incorrect for 2011 (no matter which time zone is used).
 * Second there is no precision on the tropical dates. It suggests that the sun leaves a sign on one day and enters another on the next!  As I am sure you and others here know, the solar ingress occurs at a different precise time each year and this only occasionally occurs at midnight GMT by coincidence.
 * The Tropical Dates listed are not accurate for 2011. (I have not checked Sidereal and IAU dates) For example the Sun entered (Tropical) Taurus at 10:19 (some sources say 10:17) GMT on April 20 2011.  Yet, the table lists that 'Taurus begins' on April 21 - which would not be correct anywhere not even in New Zealand!
 * The table is also misleading in that these ingress dates vary from year to year. So someone looking for their Sun Sign on this table will be misled.  This table requires lots of careful maintenance and being inaccurate this far into the year, the job is clearly not being done.  Since it can only be done manually, I suspect it will be allowed to lapse year after year given the 24 million other pages on WP that need to be updated and maintained.  This could be solved with a new page with data for every year from 1900 to 2050.
 * The IAU Zodiac is a nonsense invention. No one at the IAU claimed that their arbitrary boundaries would establish a new zodiac or if my assertion is wrong can someone please support it with a citation?  There have always been pretenders to the Zodiac. I know that Cetus whose boundaries touch the ecliptic has been proposed - why only Ophiuchus?.  I remember a book from the 70s where someone claimed a new sign, Arachnida in between Taurus and Gemini. Orion was in older proto-zodiacs - notably those based on the undulating path of the Moon. Anyone who has studied the history of the Zodiac will know that reference to Ophiuchus on this page is about as relevant as including a nearby kiosk selling tourist 'tat' in an article on the architecture of the Great Pyramid.


 * The table looks attractive and informative but it appears to be designed primarily to justify inclusion of Ophiuchus by inserting the IAU boundaries. The zodiacal symbols are already listed in a diagram. IMO the date table should be revised to inform about the two traditional and established Zodiacs only or the entire table deleted as a specious gimmick. A compromise suggestion is that the Table could be updated to include Cetus and moved to the Ophiuchus page if this page is not deleted.  This might give a fuller explanation of the controversy.  Robert Currey   talk


 * Actually I think the IAU boundaries are significant and well worth the mention. We need to remember that the zodiac is not just an astrological frame of reference but the traditional astronomical frame of reference too, so information about how it connects to the constellations - historically and currently - is of value to the page.
 * I have made some text edits to clarify the situation over the Ophiuchus confusion. I agree that it was innapropriate to draw attention to Berg's self-promotional text, so I have replaced this with a historical account of why the matter really drew media attention in the mid-1990s. If the so-called Ophiuchus (astrology) page is retained then this information may be best moved there. I personally believe it is better to cover the issue to this level of detail here, and then do away with that superflous page, and with it all the problems that attend it.


 * My remaining concern is over the paragraph in that section which begins "There have always been a number of "parazodiacal" constellations that are also touched by the paths of the planets". The relevancy of this information is lost on me, it is not appropriately sourced, and it stretches points that are highly questionable.  The fact that the Southern Fish is shown in classical maps as swallowing or swimming in the stream poured out of Aquarius' pitcher in no way means that the two constellations were meaningfully associated. A great many of the constellations were associated through connecting myths, so the passage doesn't offer much by way of relevant information and only adds further points of confusion IMO.  What does the word 'parazodiacal' mean anyway?  My recommendation is that the  entire paragraph is deleted - but I'll leave that for others to decide upon.  Zac  Δ talk   10:44, 13 July 2011 (UTC)


 * The Table of dates is very old, and wasn't created to promote the astrological Ophiuchus at all. See e.g. 2008-08-11 . BTW I think that the column "Brightest Star in constellation" could be skipped. I think it was some kind of NPOV to balance the astrological "Birth stone". --Regards, Necessary Evil (talk) 12:47, 13 July 2011 (UTC)


 * Granted that the table under 'The Twelve signs' is very old, but the 'Table of dates' refers to the IAU boundaries, which is where I feel the Ophiuchus reference is relevant astronomically. But I'm happy to go with what others feel is most appropriate. I'm not sure about deleting the brightest star column - this is really nothing to do with the associated birth stones, which I agree is irrelevant information that carries no weight historically. The brightest star information relates only to the constellations listed - so the question is whether this creates unneccesary confusion, given that the list is mainly concerned with defining the zodiacal signs, which of course have no associated star. Zac  Δ talk   13:20, 13 July 2011 (UTC)

About Hindu zodiac influences on Western zodiac
We know it is of Mesopotamian origin, so present in the Persian empire as in the Hellenistic kingdoms and consequently in India with local variations. In fact the Chinese constellation system is very different. But to say that the zodiac is unilaterally influenced by the Hindu zodiac has no historical evidence. The Yavanesvara which appeared in western India suggests a different thesis.

Other reasonable hypothesis but unfortunately without historical evidences: a)    Indo-European migration, to see Vedic and Mitanni pantheon (same Gods names). b)     The Semitic (Chaldean) origin that it is more probable as the classic authors say us. We have only these clues. We know that Accadian and Babilonian religion is linked with Sumerian astronomical/agricultural religion. The planets and stars were observered on the ziggurat temples. Example the continuity between Inanna/Isthar/Aphrodite (identify with the planet) Sin for moon etc etc. Why not for zodiac ?. Finally we know that Sumerians traded with Indus valley. But we cannot write these in enciclopedia.....

For the moment we can to affirm only that zodiac is brought by the Greeks/Yavanas in India. In future if we will have other evidence .... --84.222.74.83 (talk) 11:18, 18 July 2011 (UTC)


 * I agree. The comment lacks citation. I think it should be removed. Zac  Δ talk   11:23, 18 July 2011 (UTC)

The phenomenon of precession of the equinoxes is known to the Greeks, who use it in astronomy but not in astrology that continued to use the ancestral tropical system. We know the work of Hipparchus of Nicaea. Today in same manner in the astrology we use the ancient system and not the Hipparchus system. Ophiuchus is present in astronomical zodiac (sideral) but not in astrological zodiac (the last obviously is older than Hipparchus and it is traditional. The Sideral(Hipparchus) system appared in India astrology in the XIX century by Sri Yukteswar Giri. Attention not obviously in astronomy that already used the sidereal system to see the islamic Uluğ Beg only for an example. The paragraph that must be changed, confuses astronomy with astrology indeed both use the zodiac. --Andriolo (talk) 15:39, 18 July 2011 (UTC)

For the reasons listed above, and the confusion between astrology and astronomy about sidereal coordinates of the Hindu zodiac paragraph. And for the lack of references I propose the deletion of the paragraph.--Andriolo (talk) 18:36, 18 July 2011 (UTC). I'ven't deleted it but I changed a little the paragraph to improve a bit. In western side there are substantially two zodiacs: the astronomical (sideral without precession) with 13 constellations (attested from late Roman Empire period, but probably born in “scientific” schools in Alexandria) and the astrological (Chaldean traditional with precession ). Attention the caldeans known the phoenomenon to see Kidinnu (gr: Kidenas) that influenced Hipparchus which did the calculations. Also for the medieval Albategnius the chaldeans known the phoenomenon before greek conquest. This division does not exist in the Indian world. However the sideral system in Hindu astrology is relatively recent. --Andriolo (talk) 22:35, 18 July 2011 (UTC)

Confusing lede
The lede of this article is poorly constructed and incorrect in its details. It reads:


 * In astronomy, the zodiac (Greek: ζῳδιακός, zōdiakos) is the ring of constellations that lines the ecliptic,[citation needed] which is the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and planets also lie roughly within the ecliptic, and so are also within the constellations of the zodiac. In astrology, the zodiac denotes those signs that divide the ecliptic into twelve equal zones of celestial longitude. As such, the zodiac is a celestial coordinate system, or more specifically an ecliptic coordinate system, taking the ecliptic as the origin of latitude, and the position of the sun at vernal equinox as the origin of longitude.

The zodiac is not the "ring of constellations" - it is the mathematic division of the ecliptic, specifically designed to offer a distinct frame of reference from that of the irregularly spaced constellations. This lede makes it sound like there is an astronomical zodiac AND an astrological zodiac, which is not the case. The last line of the lede is correct - the zodiac is and always has been used for astronomical measurement and the astrological meanings extend from this, but do not generate a separate form of division. There is a lot of confusion here between the ecliptic and the zodiac - the paths of the Moon and planets do not lie within the ecliptic, they lie within the zodiac - (the belt of celestial space that extends 8-9° either side of the ecliptic in order to contain the apparent paths of the observable planets). Also, it is not just astrologers that have used the signs of the zodiac to divide the ecliptic into twelve equal parts - this was the standard astronomical frame of planetary movement until recently, and the one that was traditionally used to record the positions of stars as well as planets.

I notice that the current lede is unreferenced, goes back to the initial version of the page, and doesn't adhere to what is said in the main body of the article. Does anyone want to defend the lede as it stands or should I suggest a rewrite that clarifies these issues? Zac Δ talk   20:24, 26 July 2011 (UTC)


 * The confusion is very evident even in the lede and requires disambiguation. This is usually resolved by creating separate articles and cross-referencing. Zodiac:astrology should be disambiguated from zodiac:astronomy, and zodiac:astrology should be further disambiguated into tropical and sidereal. And then there's the Chinese zodiac. It may be the only way to put an end to all the confusion, which it seems some people are only too happy to perpetuate. A good, well researched discussion on the tropical and constellational zodiacs, written expressly to resolve this recurring confusion, appears in a recent article, "Toward and Understanding of the Two Zodiacs" by Glenn Perry PhD in the April 2011 issue of ISAR International Astrologer, pp 53-63. Ken McRitchie (talk) 14:03, 3 August 2011 (UTC)


 * Hi Ken, I don't agree with the suggestion that "Zodiac:astrology should be disambiguated from zodiac:astronomy" - this implies that astrologers have been using a different zodiac from astronomers which is not the case. This just needs a clear explanation of what the zodiac is and what it was designed for (ecliptic-measurement). I agree that there should be differentiation between the western zodiac and the Chinese one which is entirely different in its composition.  Within the western system there is one basic structure and always has been since it was originated, differentiated only by the position of its commencement point: the vernal point for the tropical zodiac and a fixed star for the sidereal zodiac. I think this article can explain the issues in the western zodiac clearly enough, but it's going to require time and attention because at the moment there are a lot of elements of confusion on this page. Zac  Δ talk   14:16, 3 August 2011 (UTC)


 * The section "In modern astronomy" is a complete screw-up of misinformation between zodiac signs and constellations. This gives the false impression that there is some kind of modern astronomical zodiac which is used as an ecliptic measurement system in a way that the tradtitional astronomical zodiac (used by astronomers and astrologers alike) did not. The only difference is that modern astronomers have ceased to use sign-symbols as short-hand annotations and now use absolute longitude only - I presume to create a sense of detachment from a system it has historically shared with astrology. But I'm pretty sure that it's a more recent convention than this passage implies and will try to look into when astronomers ceased to using sign notations in their planetary position tables. I would think, more likely to be 19th or 20th century than 18th century.  Zac  Δ talk   14:31, 3 August 2011 (UTC)

Zodiac as a measurement system
There appear to be about four measurements that involve the Zodiac in a broad sense.
 * 1) Ecliptic longitude, measured from the March equinox of date. Modern astronomers prefer the notation 0–360°. Western astrologers prefer the notation of a zodiac sign name followed by the number of degrees into the sign. I don't know what notation Hindu astrologers prefer.
 * 2) Ecliptic longitude at a stated epoch, such as J2000.0. Since the convention is that a measurement at any other time is transformed using a model for precession and nutation to show what the measurement would have been at the beginning of AD 2000, this is actually a sidereal system, comparable to that used by the Hindu astrologers.
 * 3) A patch of the celestial sphere with dimensions of 30° ecliptic longitude by approximately 16° celestial latitude, in which a celestial body may be located at a given time. Whether the celestial latitude and longitude of date, or of a particular epoch, is intended should be stated or implied from context.
 * 4) A constellation associated with the Zodiac in which a celestial body may be located at a given time. The Centre de données astronomiques de Strasbourg has a web page which makes available the boundaries of IAU constellations both at the epoch 1875 (which was the epoch used for the original definition) and at the epoch 2000. So the IAU agrees with tradition that the constellation boundaries, whether vague (traditional) or exact (IAU), are fixed to the stars and not to the March equinox. Jc3s5h (talk) 15:08, 3 August 2011 (UTC)


 * Hi Jc3s5h - thanks for commenting. (I was hoping you would)
 * From what you describe, 1 is the bog-standard tropical zodiac and so is 3.
 * I'm not sure I understand your explanation of 2. This sounds to me like it's the bog-standard tropical zodiac too, but simply with a date adjustment for the vernal equinox. Maybe I haven't understood properly, but it seems to describe the type of thing is done regularly by astrologers working on historical charts in order to take the effect of precession into account. Can you clarify why you think it describes a sidereal system (which takes its zero point from a fixed star) rather than the tropical system (which takes its zero point from the VP)?
 * 4 - we have to be clear to establish that these are only zodiacal constellations (ie, constellations that cross the zodiac belt of the ecliptic) and not part of the zodiac system of a mathematical division into 12 equally spaced 'signs'. The background constellations have always been referred to in this way, but it doesn't comprise a formal system of zodiacal reference. I may be mistaken (again, it would help if you could clarify), but I assume that modern astronomers don't use the irregularly spaced constellations in order to catalogue the ecliptic positions of planets by celestial longitude, but that they only use absolute longitude (or other systems such as RA and declination). Are you able to confirm, or do you know otherwise? Thanks Zac  Δ talk   17:25, 3 August 2011 (UTC)


 * With case 2 the coordinate system is fixed to the stars as the coordinate system existed as of the beginning of AD 2000. Similarly, the Hindu system uses a coordinate for celestial longitude as it existed around 2000 years ago. I will give a more specific example but it will require me to poke around in the Multiyear Computer Interactive Almanac. Jc3s5h (talk) 18:09, 3 August 2011 (UTC)

Here is the example I promised. There is a distant radio source in another galaxy, which the International Earth Rotation Service designates as "0109+224". It's located in the constellation Pisces. Because it is so far away, it isn't expected to have any observable change in direction, compared to the average of all the distant stars. So it has been designated one of the radio sources that make up the International Celestial Reference Frame. Here is a table of its right ascensions at the epoch J2000. (Right ascension (RA) is similar to celestial longitude, except it is measured along the celestial equator, instead of the ecliptic. Unfortunately MICA does not compute celestial longitude for J2000, but RA will serve our purpose.) We know the radio source isn't moving, and all the coordinates are the same, so this shows us that the J2000 coordinate system always gives the same coordinates to fixed stars.

On the other hand, we can calculate the ecliptic longitude of the same radio source for the equinox and ecliptic of date: We see that the celestial longitude is changing due to precession. This is because we are calculating based on where the moving equinox is in 1800, 1900, and 2000. Jc3s5h (talk) 18:58, 3 August 2011 (UTC)


 * I think I understand the example well enough (I printed everything out to study what you wrote). However, the example suggests that once the reference is changed to celestial longitude rather than right ascension, its reference is to the tropical frame of reference not the sidereal one. Otherwise the celestial longitude wouldn't change as it does in the 2nd table.  The change is caused by the precessional drift which affects the tropical zodiac, not the sidereal zodiac. That's why western astrologers need to adjust for precession when considering historical charts.  As you say yourself, it's because of the way the equinox has moved between 12800-2000 - if this were using the sidereal system it would be unaffected by that movement. Do you see what I mean?  Zac  Δ talk   19:31, 3 August 2011 (UTC)


 * I'd agree with what you're writing, with two exceptions. First, I imagine "12800" is a typo. Second, either system of coordinates, equatorial (with right ascension) or ecliptic (with celestial longitude) can be either "of date" or referenced to a certain epoch, like J2000. It's just that certain combinations are commonly used with astronomers, and others are not. The ecliptic system isn't usually used with J2000, so MICA won't output results in that system. It wouldn't be too hard to write a program to convert to that system if I wanted to, but there is a limit to how much work I'm going to do for this discussion. Jc3s5h (talk) 19:50, 3 August 2011 (UTC)


 * We can dispense with the first disagreement: it's a typo :) On the second, I think your input is really useful so I want to make sure we understand each other. R.A. is a red-herring - it's not at all relevant because it's not related to the zodiac.  If the system you demonstrate here isn't usually based on celestial longitude then we're not talking about a 'zodiac system'. Historically astronomy was almost entirely focussed on the zodiac and the use of celestial longitude, because this was the best frame of reference for visible planetary movement.  But modern astronomy has different concerns to traditional astronomy, which makes the zodiac redundant to its current needs. (Not the case for astrologers because their concerns have remained the same as in the past: the measurement of planetary cycles as they relate to the Earth - they still need to utilise the geocentric frame of reference).


 * It's possible to convert any celestial reference from one system to another but the only point of consequence here is that when the conversion is made, it is usually made to celestial longitude which commences from the vernal point, which means that we are talking about an ecliptic-reference which is tropical, not sidereal (tropical means 'turning'. ie, shifting/involving precession). There is a big clue in the fact that when modern astronomers do speak out about the subject of the zodiac they are usually quick to make a big thing about precession, as if astrologers don't account for it. (They do). Yes, it would be possible to program a different sort of conversion, but if you have to do this yourself then how could we refer to it as an established convention that is notable because the modern astronomical community is known to make use of it?


 * Having said all that if you want to propose a revision for the section headed 'In Modern astronomy' to include substantiated details of how modern astronomers use the zodiac in a way that differs from the historical use I would try to help out as a reader who might struggle to understand the concept, just as the general reader might. At the moment that passage is very confusing and implies that there is an 'astronomical zodiac' which is 'astronomical' and an astrological one which is not. It needs to be corrected to make it clear that the traditional western zodiac has always been an astronomical frame of reference. It aquired seasonal symbolism because astronomy is never free from the relevance of time, and time (when presented as a calendar) is never free from symbolic associations - astrology never used a zodiac that was separate from the astronomical one Zac  Δ talk   21:10, 3 August 2011 (UTC)


 * A more extensive system for computing the position of solar system bodies is Horizons from the Jet Propulsion Laboratory. If you look at this part of the documentation you will see that "Ecliptic and mean equinox of reference epoch" is supported, and that the reference epoch may be "J2000.0 or B1950.0". So use of that coordinate system is clearly established, just less popular than some of the other ones. I have not used Horizons myself yet, since it is less user-friendly than MICA. Jc3s5h (talk) 22:59, 3 August 2011 (UTC)

Zac, about your statement "From what you describe, 1 is the bog-standard tropical zodiac and so is 3." To me, an area of sky is a different concept from an angular coordinate. So for 1, I could say that right now the ecliptic longitude, using the ecliptic and equinox of date, for the star Vega is 285.49454°, even though its celestial latitude, + 61.73448°, means that it is far outside the zodiac. For 3, the patches of sky that define different signs can be either tropical or sidereal, whichever is stated or implied in the text. Probably the astrological description "tropical" or "sidereal" is more appropriate than "of date" or "J2000" because if an astronomer were to say an object is in Aries (without further qualification) he would mean it is in the constellation Aries; I have never heard of astronomers using zodiac signs as areas of sky that an object could be located in. Jc3s5h (talk) 23:25, 3 August 2011 (UTC)

(Just had an edit conflict so will post what I was going to post and then look at your new post above):
 * I see the reference but I'm unsure why you say "use of that coordinate system is clearly established". The only thing that the phrase mean equinox of reference epoch establishes is that Horizons uses the tropical system (which commences from the equinox), not the sidereal one (which doesn't). And I'm guessing it uses absolute longitude rather than zodiacal sign reference, is that right?


 * Again, this is what you describe in the first definition but with the effect of precession factored in. It's a mistake to assume there are two separate zodiac systems - one being of the current date and another making use of a certain epoch's starting point. This is just one system making recalculations for differences in time, and that is the notable feature of the tropical zodiac - it shifts against the stars and so it has to be recalculated for any period in which it is used. Astronomers have always used references to epochs for this, because the shift is barely perceptible unless significant time frames are involved (although of course, software programs can be used to create precise calculations for any give date). Do you think the point of interest here lies in the fact that modern astronomers can still make use of the system, even though it's not popularly employed, and that they tend to use specific epoch dates for reference ? Zac  Δ talk   23:50, 3 August 2011 (UTC)


 * Zac wrote "I see the reference but I'm unsure why you say 'use of that coordinate system is clearly established'. The only thing that the phrase mean equinox of reference epoch establishes is that Horizons uses the tropical system (which commences from the equinox), not the sidereal one (which doesn't)."


 * No, not at all. You couldn't actually get output that is labeled "mean equinox of reference epoch", you would have to choose either "mean equinox of B1950" or "mean equinox of J2000". So if we concentrate on the second choice, the system is based on the direction of the equinox at the beginning of 2000. That direction is fixed relative to the distant stars, which are so far away that they the relative motion among them is too small to measure. This is just like the sidereal zodiac, which is fixed to the position of the equinox in about 500 BC. This is in contrast to the "of date" system, which is relative to the position of the equinox at the moment of observation.


 * Of course, the astronomers do update the epoch from time to time, about every 50 to 100 years. So if you wished, you could think of the reference epoch system as "tropical in jumps" and the "of date" system as "smooth tropical". Jc3s5h (talk) 00:19, 4 August 2011 (UTC)


 * Maybe I’m misunderstanding you completely but I think you’re confused in what you’re saying about the direction of the equinox being fixed relative to distant stars. The vernal equinox is determined by the point at which the ecliptic intersects the equator, and that’s the major principle of the tropical zodiac – that the equinox is the point of commencement which shifts in relation to the constellations. The sidereal zodiac is not fixed to the equinox of about 500 BC, it’s fixed to the stars.


 * With regard to your earlier post, the ‘zodiac belt’ is traditionally described as extending 8-9° either side of the ecliptic, but all this means is that this is the area of interest (geocentically, in regard to the visible planets) because this contains their extremes latitudes N or S of the ecliptic. So the visible planets remain within the belt of the zodiac but the stars don’t – doesn’t matter the system still works as a reference for bodies outside the zodiac.


 * To put this another way, the zodiac is centered on the ecliptic and it’s the ecliptic that really matters as the astronomical frame of reference – it gives the 360° reference for celestial longitude, but it’s also the line that determines the measurement of celestial latitude, North or south of the ecliptic.  We can’t define the position of a body in space from longitude without the latitude too (just as we can’t using RA without the use of declination).


 * I’m not surprised about what you say of astronomers only talking about objects in the constellation of Aries. That’s what I’d expect. But whereas you say Vega is 285.49°, an astrologer (and astronomers traditionally) would say it is at 15°♑ 49’ (ie, 15°49’ Capricorn) because each sign is 30° and Capricorn as the 10th sign commences at 270° in absolute longitude (or what you would just call 'celestial longitude'). This would be accompanied by the celestial latitude location.  Astronomically the reference to signs is just like a shorthand notation. It works in just the same way that we call today the 4th of August, rather than the whatever number of day it is now from New Year's day.  But it’s true the system is not commonly used by astronomers anymore – I think the only reason it was dropped was to dissociate astronomy from dubious connections with astrology, but dropped it definitely has been.


 * Got to sign off now, it’s early hours for me. Not sure how this is going to be best worked into the content – any ideas on that? Be careful about jumping to conclusions on the sidereal issue. Maybe I'm the one misunderstanding you, but I'm just not seeing your argument  Zac  Δ talk   00:42, 4 August 2011 (UTC)

Zodiac as coordinate arbitrary break
Zac wrote "Maybe I’m misunderstanding you completely but I think you’re confused in what you’re saying about the direction of the equinox being fixed relative to distant stars. The vernal equinox is determined by the point at which the ecliptic intersects the equator, and that’s the major principle of the tropical zodiac – that the equinox is the point of commencement which shifts in relation to the constellations. The sidereal zodiac is not fixed to the equinox of about 500 BC, it’s fixed to the stars."

In the J2000 system, the origin of longitude is where the vernal equinox was in 2000, and it never moves with respect to the distant stars. If observe a supernova tonight with a celestial longitude of 50° relative to tonight's equinox, I could transform it to the J2000 system using a web page provided by NASA, and find the J2000 longitude is 49.83810°. Or, I could use the same page to transform it to something close to what the Babylonians used when they set up the system and which was inherited by the Hindus and is the basis of their sidereal zodiac. Supposing they set up their system in -500 (or 501 BC) that would be J-500, and the latitude would be 15.10586°. So J2000 and J-500 are conceptually the same thing, it's just the magnitude of the transformation that is different. Jc3s5h (talk) 01:07, 4 August 2011 (UTC)


 * "the origin of longitude is where the vernal equinox was in 2000" - which is why I say this is using the tropical system - the use of the vernal equinox for the origin of longitude is the very defintion of the tropical system. "and it never moves with respect to the distant stars" - but isn't that because you've fixed the date of reference; ie, it's not the system itself which is fixed to the stars in the way that the sidereal zodiac is.


 * This doesn't sound any different from what is done by astrologers using the tropical zodiac (also using the year 2000 epoch) which is why the star position of Vega you reported is the position an astrologer gets by use of the tropical zodiac reported as signs and degrees. A sidereal astrologer, on the other hand, would get a very different position to the one you reported.


 * Here's a suggestion that might settle this more easily. Take one of the prominent fixed stars. Post the longtitude and latitude position for today and then adapt your reference and post what it was in the year 1500 (AD). I'll check how that compares with what the usual use of the tropical zodiac reports. Tomorrow :)  Zac  Δ talk   01:35, 4 August 2011 (UTC)


 * I will do as you ask. In the mean time, notice that the amount of longitude shift from tonight to J2000 is about 0.16°. That might seem negligible to an astrologer. But if a professional telescope was pointed in the wrong direction by that amount, the object of interest would be outside the field of view of the telescope. From the point of view of an astrologer, there is a big difference in the sidereal longitude of 501 BC and tropical longitude because the sun and planets will be in the wrong sign if you use the wrong system. From an astronomers point of view, there is a big difference between sidereal longitude of 2000 and tropical longitude (that is, using the equinox as of the moment of observation) because if you use the wrong one, the object will be in the wrong telescope field of view. Jc3s5h (talk) 02:33, 4 August 2011 (UTC)


 * What you are describing is the only effect of precession. It's not something that astrologers or historical astronomers have not realised or fail to take account of (about 1° every 72 years). "From the point of view of an astrologer, there is a big difference in the sidereal longitude of 501 BC and tropical longitude because the sun and planets will be in the wrong sign if you use the wrong system" - no, at that time the systems were coinciding and the big difference didn't exist. It took about 2000 years for them to seperate by the distance of one sign. This is not really a distinction based on astronomers v astrologers point of view - the site you linked to is providing a simple conversion tool. All astrology calculation software has this sort of thing built into it, it's only printed tables and ephemerides that will give star positions by epoch, with the expectation that the necessary precessional calculation is performed to give an exact location for any date (for those who do it manually as it was done in the past). This is why there is a lot of work to be done on this page, to make the whole precession issue clearer  Zac  Δ talk   09:24, 4 August 2011 (UTC)

Here is the example you asked for

Both stars are relatively bright (about 3rd magnitude) and not very distant, so they have some proper motion (they appear to move relative to the distant background stars). I did a rough calculation and found they would move by as much as 0.15° from -500 to 2000, so I rounded all the degree measurements to the nearest 0.1°.

Markab is in Pegasus and is fairly close to today's origin of celestial longitude. Hamal is in Aries, and is close to the origin of longitude as it was in -500. Jc3s5h (talk) 13:24, 4 August 2011 (UTC)


 * Thanks. Just in case you don't realise, astrologers (unless they are not very good) know the constellation placement of stars as well as the zodiac sign positions. The star meanings depend on constellation reference, so even though zodical longitude is used to define position, it's necessary to develop familiarity with the constellation details too.


 * I've reproduced your table below with your original entries in square brackets. You can see from my insertions that we are using the same tropical zodiac system - the figures match.  Sidereal astrologers would not get anything near these positions for 1500 and 2000 (except in latitude which hardly varies).


 * The only difference between your entries and mine (which show the zodiacal longitude reference first and then the absolute longitude equivalent afterwards) is that your figures are using fractions of degrees in decimal, rather than the sexagisimal format which calculations in minutes, degrees and seconds ought to be using - you can see this where you have tabulated the position for Markab for 2000 as 353.5 (ie, 353½), whereas mine is 353°30' (rounded up), 30' being half a degree, which is what your entry is expressing.


 * So that you can see there's no doubt, and I'm not just making the figures up, the thumb below gives a partial screenshot from the astrological software I used to get the positions (this one shows the 500 BCE positions). It gives other information that I cut, and allows calculation according to various sidereal systems, but I have it set to use the tropical zodiac, the default option. If you click on it, you'll see the details I've used. Zac  Δ talk   15:00, 4 August 2011 (UTC)



Jc3s5h, in light of this, are you happy to accept that there are not four different zodiac systems as suggested at the top of this discussion section, but that points 1, 2 and 3 are all details that relate to the tropical zodiac? It would be good to clear up these issues before I propose edits on the content. The relevant points of clarification I suggest are: Would you (and other editors) agree – or is there anything I’ve missed? I also hope to add useful information on the roots and historical development of the zodiac system. Zac Δ talk   15:35, 4 August 2011 (UTC)
 * 1) The western zodiac is a tropical one (we don’t need to state that this is the case both astronomically and astrologically because it shouldn’t really be in dispute; but we should remove confusing references that might be interpreted as suggesting otherwise).
 * 2) The sidereal zodiac which is used by Hindu astrologers uses the same mechanics and differs only in its commencement point (giving coverage as to why this is, and explaining the precession element clearly).
 * 3) Clarification of what is meant by describing a constellation as a ‘zodical constellation’ so there is no confusion that makes the reader think that a constellation is the same as a zodiac sign.


 * I'm not surprised the figures agree, I have no doubt that astrologers can do precession calculations. What I'm getting at is that you are applying the term tropical longitude to two concepts that are different to astronomers. The first system is J2000, which is useful for gathering observations taken at different times and expressing in the same system so they can be compared. The second system is the "of date" system, which means the equator and equinox as they exist at the time of an observation. This is useful for pointing telescopes so that the object will be in the telescope's field of view.


 * Let's say a child is born this year on August 23 at 1121 UT1 on the grounds of the Royal Observatory, Greenwich. Using the equinox and equator of date, the cellestial of the Sun is 150.0024°, or 0°♍ 0'9" using notation akin to your previous post. But if the ecliptic and equinox of 2000 is used, the cellestial longitude of the Sun is 149.8374°, or 29°♌50'15". So I suppose it would be important to the Western astrologer to use the correct system, because using the wrong one gives the wrong Sun sign. So which of the two systems would the Western astrologer use? I don't think I can move on to your most recent set of questions until I understand your answer to this. Jc3s5h (talk) 16:20, 4 August 2011 (UTC)


 * I want you to be fully satisfied so there’s no lingering doubt. This is not a case of two systems; just one system being referenced to two different dates. In basic terms J2000 values give the positions of the year 2000 of the Julian calendar, used as an astronomical convention to make sure all astronomers reference astronomical positions of a collaboratively agreed date. Whereas the ‘of date’ reference is to the position of the actual event (not the current date). Agreed?


 * Imagine we were discussing right ascension instead – would you say there are two different systems of right ascension, one system that uses the J2000 position and another system which uses the ‘of date’ position? No - it’s the same astronomical frame of reference, just giving different values for how astronomical bodies move in time.


 * Astrologers don’t talk about ‘J2000’ - although, historically, tabulated star positions would be given for every 50 years or so, and then manually adjusted by calculation to derive the correct value for any date. Also, astrologers don’t have the phrase ‘of date epoch’ in their terminology – but to answer your question, that is what is used in determination of the vernal equinox for the year of any event, because the initiation of a new zodiacal cycle (0° ♈) is calculated precisely for the time that the Sun crosses the equator in March of that year. All astrological calculations are made as precisely as they are able to be. Astrology also refers to different longitude positions at different stages of life; and again the effect of precession is accounted for, so that the zodiac positions are always astronomically accurate. This is surely the same as the astronomical approach to deriving exact positions for any given time.


 * BTW, astrologers also get their astronomical time references from sidereal time, which is then converted to local time for the event (I mention this only because we are talking about epochs and time references, and the issue of sidereal time may have become the point of confusion). Does that explain? Zac  Δ talk   18:16, 4 August 2011 (UTC)


 * "I want you to be fully satisfied so there’s no lingering doubt. This is not a case of two systems; just one system being referenced to two different dates. In basic terms J2000 values give the positions of the year 2000 of the Julian calendar, used as an astronomical convention to make sure all astronomers reference astronomical positions of a collaboratively agreed date."
 * It seems we need to define "system". If we look at pages B26–7 of the Astronomical Almanac for the year 2011 we see 8 different "systems" listed, including, among others, "mean equator and equinox of J2000.0", "mean equator and equinox of date", and "true equator and equinox of date". Since the difference between "true" and "mean" are quite small, I've been neglecting them for this discussion. But it's clear that in astronomy, when you change which equinox you are measuring from (where the equinox is right now, or where it was in 2000) you have changed to a different system.


 * " Whereas the ‘of date’ reference is to the position of the actual event (not the current date). Agreed?" In the "of date" system, celestial longitude is measured beginning at the March equinox as it is located at that moment, along the ecliptic, to a point directly above or below the object of interest. But since the equinox moves rather slowly, finding its position once per day will be accurate enough for many purposes.


 * "Imagine we were discussing right ascension instead – would you say there are two different systems of right ascension, one system that uses the J2000 position and another system which uses the ‘of date’ position? No - it’s the same astronomical frame of reference, just giving different values for how astronomical bodies move in time." I would say that for moderate precision work, there are two systems of RA and declination, the J2000.0 system and the "of date" system. For higher precision, the "of date" system must be divided in two, the "true" system and the "mean" system. And then there are several more that were introduced in the 1990s and 2000s to take full advantage of the precision possible with Very Long Baseline Interferometry. Jc3s5h (talk) 18:59, 4 August 2011 (UTC)


 * Yes, but the use of mean values and true values (also used in astrology) is not of consequence to this page. You seem to be talking about minor systems of employment rather than the major frames of reference this page is concerned with - only two: Tropical and sidereal. The sidereal system can also use various forms of commencment. Perhaps this is information that goes into the details of relevant sections or a footnote.  Zac  Δ talk   20:47, 4 August 2011 (UTC)

Unfortunately the astronomical community has preempted many of the words we might want to use; we've already discussed "system". You stumbled upon another preempted word: "frame". For example, there is the International Celestial Reference System, which describes in detail the concepts and goals of the system, and the International Celestial Reference Frame, which is the practical realization of the system. The practical realization consists of a list of 212 extragalactic radio sources and their positions. Perhaps we could say there are two four approaches for coordinate systems related to Earth (with astrological names in italics when they differ from equivalent astronomical terms):

† On the date given the equator and ecliptic had a certain orientation, and the intersection of those planes was a line that established the equinoxes. The position of the object is given relative to those planes and the March equinox as they were oriented at the date listed in the date column. The object who's position is being given is not necessarily transformed to were it was at the time of the epoch. Jc3s5h (talk) 21:52, 4 August 2011 (UTC)


 * "The practical realization consists of a list of 212 extragalactic radio sources and their positions. Perhaps we could say there are two four approaches for coordinate systems related to Earth ..." - Sorry, I'm knowledgeable in this subject, but I'm struggling to understand what you are trying to say that is of relevance to this page's theme. The one thing that has been clarified is that these are tropical references, not references to a sidereal system such as the Hindu astrologers use: the argument you presented. This is a page of information designed for members of the public with all levels of prior-experience, so the explanations need to be clear, not obtuse, overly technical, or difficult to comprehend. And ultimately this page needs to have reliable information about the well established facts. This sounds a little too much like speculation on your part to propose original thoughts that are not based on established knowledge or reliably sourced mainstream information about the zodiac.   Zac  Δ talk   23:03, 4 August 2011 (UTC)


 * Perhaps I could understand your position by having you define "sidereal system" in a general sense, without it necessarily having been set up around 500 BC. Jc3s5h (talk) 23:21, 4 August 2011 (UTC)


 * You know, when I read that, my immediate thought was "surely, it's explained on the page". But no, I've just checked - I'm a bit astronished to realise that the page doesn't have a clear discussion of this, apart from suggesting it's what Hindu astrologers use, and then not being very clear about it. The sidereal zodiac is exactly the same as the tropical zodiac in being 360° divided into 12 equal divisions of 30° each (named Aries, Taurus, etc), but instead of commencing from the vernal equinox as the zero degree as the tropical zodiac does, its commencment point stays permanently aligned to a fixed star reference. It's a little more complex than that in its details, because there are various systems according to different thoughts on what is the best sidereal poistion to maintain. The Hindu sidereal system is permanently aligned to Spica but it places 0° Libra at the position of Spica (which is 180°) so the commencement point of 0° Aries is always opposite to Spica.


 * The two systems were thought to pair up around 200 AD. Hence, since the vernal equinox drifts about 1° every 72 years (relative to the fixed stars); over the last 1800 years the two systems have separated their initial measuring points by about 25°. So whereas we both calculated the position of Hamal in the year 2000 at approx 8° Taurus (or 38° absolute longitude - you would probably just say 38°); in the sidereal system it is charted as approx 13° Aries (or just 13°). This is why I'm saying that everything you are talking about is making use of the tropical system, not the sidereal system. There is a substantial difference between these two systems in the data they produce, but the only conceptual difference in the systems is that the commencement of the circle of longitude measurement in the tropical zodiac is permanently aligned to the equinox (or vernal point), whereas the sidereal system ignores the vernal point (and so ignores the issue of precession) in favour of alignment to a fixed star.


 * BTW, when the zodiac was set up originally by the Babylonians, as a mathematical division of the ecliptic into 12 equal signs, it was designed to be a calendrical device that had its commencement at the equinox, so I don't accept the view that the Babylonians had anything but a tropical zodiac in mind Zac  Δ talk   00:25, 5 August 2011 (UTC)


 * OK, so I would say that ecliptic latitude and longitude "of date" are exactly equal to the tropical system, and there are many notations that can be used, depending on the needs of the moment (sign + number of degrees from eastern edge of sign, degrees, hours, radians, revolutions). There is no system used by astronomers that has all the major features of the sidereal system. For example, there is no numerical coordinate system used by astronomers that has 12 uniform divisions that approximately corresponds to the location of the zodiac constellations at the time the names were assigned. Up to this point, there is no coordinate system that is intended to remain fixed to the distant stars and remain in permanent (eg, 1,000 years) use. The ICRS seems like it could fill that role, but it's only been around a decade or so; it's much too soon to see how that will turn out.


 * Epoch systems like J2000 are a hybrid. As with the sidereal system, distant stars with no measurable proper motion always have the same coordinates. As with tropical system, just by glancing at the longitude of the Sun, you have a good enough idea of what season it is to plant crops or know whether it's time to put the overcoat in the attic. The durability of J2000 is intermediate too; it gradually took over from the B1950 system, with the IAU recommended switchover being in 1984. There is no schedule to replace it, perhaps it will last 100 years. So this is intermediate between the sidereal system that has lasted around 2000 years, and the "of date" system, where an individual calculation of the equinox location might be used for a second or a year, depending on the precision of the work being conducted. Jc3s5h (talk) 00:56, 5 August 2011 (UTC)


 * The last sentence is still not right - you need to give this some thought. J2000 is an epoch system, not a different definition of the zodiac. It's only a date of reference for the tropical zodiac using all of the T.Z. features.  It doesn't commence its zero point from that date (1st Jan); it uses the 'of date' vernal equinox of that year, and as such it does no more than reference the tropical zodiac positions of that year, as would be the case if all astronomers decided to use a reference system to any other date before or after it.


 * It has no relevance at all to the sidereal zodiac. (I'm wondering why you refer to the sidereal zodiac as having lasted 2000 years. It was the tropical zodiac that was introduced by the Babylonians - specifically designed to create mathematical division of the ecliptic aligned to the equinoxes and solstices, instead of positions that relied on unreliable visual proximity to stars). Anyway, give this some thought. Remember that the page needs to build its content on independently sourced references, not what you or I think; so if you do think J2000 matters in any way (I don't) then you need to find some authoritative source that has made the argument already. Zac  Δ talk   08:57, 5 August 2011 (UTC)

Zodiac as coordinate, 2nd break
Probably the J2000.0 system does not need to be mentioned in the article. Probably the "of date" ecliptic system should be included because it is really just another name for the tropical zodiac longitude measurement, with (except in quite old texts) different notation. The reason I would like people to clearly understand J2000 is so the mention of the "of date" ecliptic system will be written in a way to exclude the J2000.0 system. So I'm not advocating inclusion, I'm advocating carefully written exclusion.

About the statement "It doesn't commence its zero point from that date (1st Jan); it uses the 'of date' vernal equinox of that year", no, that's not true. It always use the vernal equinox of 2000. I believe this passage from page 13 of P. K. Seidelmann (ed.), Explanatory Supplement to the Astronomical Almanac, (Sausalito: University Science Books, 1992) supports that. "In principle it is possible to obtain a standard celestial coordinate frame that is fixed in space by using the frame that is appropriate to an arbitrarily chosen instant of time, which is known as the standard epoch. The positions of the equator and equinox for such a standard epoch cannot be observed directly, but must be specified by adopting a catalog of the positions and motions of a set of stars or other celestial objects that act as reference points in the sky. The standard epoch is now J2000.0, although the epoch B1950.0 has been used for much of this century." Jc3s5h (talk) 13:54, 5 August 2011 (UTC)


 * Your first comment was reassuring and I like the idea of carefully writing text that brings clarification :) It would be very good to have a statement about whether modern astronomers still make use of this system, to what extent, and how conventions have or have not changed. I'm not sure I follow the second comment - isn't your argument that the 'of date' reference uses the VP of that year?  If J2000 relies on a date in 2000, and uses the VP of 2000, why do you call it incorrect to say it uses the 'of date' vernal equinox of that year ??  Zac  Δ talk   14:16, 5 August 2011 (UTC)


 * I understood your remark to mean that J2000.0 used the vernal equinox of January 1 in the year that the observation took place in. But reading it again, I see that isn't what you meant. Jc3s5h (talk) 14:20, 5 August 2011 (UTC)


 * OK - reading it again now I can see how you might have thought that. It wasn't what I meant but I should have been clearer. Zac  Δ talk   16:19, 5 August 2011 (UTC)


 * Thanks for the comment. I agree with your latter comment, obviously. I'm not sure if you were reporting a view or proposing your own views that "the basis of astrology is the influence of "the stars". Its basis is obviously much more than about "the stars", and it has to be remembered that, historically, that phrase is a colloqialism for anything of celestial influence. The main astrology article actually covers this quite well in the section headed 'Etymology and basic definitions'. That said, I am not trying to deny that the stars matter too. --   Zac   Δ talk! 23:07, 6 August 2011 (UTC)

Cetus and Ophiuchus as a Parazodiac
In ancient times, Cetus could been part of the constellation Pisces and Ophiuchus served for the 8th astrological month we now associate with the constellation Scorpio, or possibly Libra was either a subgroup of stars with the constellation Virgo. The ancient astrologers in India, Persia and Babylonia once had an "Arachnida" constellation for a zodiac but was phased out along with the concept of Orion and Perseus when the sun's orbit traveled farther south on the eliptic and the North Astronomical pole moved a few degrees away from the constellation of Draco. We would later have reimagined Scorpio, Aquarius and Gemini from the former "Phoenix", "Eagle" and "Hawk" constellations to the current designs of an Scorpion, the Water Carrier and the Twins. 71.102.3.122 (talk) 06:39, 12 November 2011 (UTC)


 * Please provide your sources. The ecliptic (the Sun's apparent orbit) does not move much over thousands of years among the stars. According to the IAU 2006 precession equations, the ecliptic has shifted only 0.67° over 5000 years (π$A$). This is insignificant compared to the size of constellations so has no affect on which constellations are zodiacal. You are thinking of the movement of the celestial equator, which has an accumulated lunisolar precession ψ$A$ (the angle along the J2000 ecliptic due to the movement of the equator) of 69.41° in 5000 years. See Williams 1994, p.720, Fig.1 and Capitaine P03, p.582, §7.1. Even though the celestial equator and the celestial poles do move significantly, they only affect which ecliptic constellations contain the equinoxes and solstices — they have no affect on which constellations are along the ecliptic. However, the constellations to which stars are assigned differ significantly among different cultures. Even the contellations in the Western tradition have changed over human history. Although the Babylonians included Libra (the balance) among their zodiacal constellations, Ptolemy did not. Instead, Ptolemy called its stars Claws (of the scorpion). Furthermore, Ptolemy clearly lists many stars that are near but outside named constellations, that is, outside the outlines of the mythical figures. Ptolemy first lists constellations north of the zodiac (including Ophiuchus), then twelve zodiacal constellations which are identical to the modern constellations except for Claws instead of Libra, and then those south of the zodiac. See Ptolemy's Almagest annotated and translated by G. J. Toomer, Book 7. The scorpion is an arachnid, that is, it has eight legs. Furthermore, its claws, as attested by Ptolemy, are not part of the constellation anyway. The shape of its bright stars evoke an image of the curved tail of a scorpion, rather then the compact body of a spider. — Joe Kress (talk) 03:25, 15 November 2011 (UTC)

Good article?
If there is one astrology/astronomy article that is a priority to take to good article and featured article, it is probably this one. Itsmejudith (talk) 21:35, 18 November 2011 (UTC)


 * The article is not exactly accurate in my opinion and needs more citations in some paragraphs 91.138.238.198 (talk) 16:24, 19 November 2011 (UTC)

Paragraph needs citations
The following paragraph in the page makes some claims without any citations:

'''The Babylonian star catalogues entered Greek astronomy in the 4th century BC, via Eudoxus of Cnidus and others. Babylonia or Chaldea in the Hellenistic world came to be so identified with astrology that "Chaldean wisdom" became among Greeks and Romans the synonym of divination through the planets and stars. Hellenistic astrology originated from Babylonian and Egyptian astrology [CITATION NEEDED HERE]. Horoscopic astrology first appeared in Ptolemaic Egypt [CITATION NEEDED HERE]. The Dendera zodiac, a relief dating to ca. 50 BC, is the first known depiction of the classical zodiac of twelve signs.[CITATION NEEDED HERE]'''

The Hellenestic astrology from what i know IS NOT originated from the Egyptian and has differences compared to the Babylonian 91.138.238.198 (talk) 16:21, 19 November 2011 (UTC)

Other zodiacs?
Shouldn't this article mention the other zodiacs (Chinese, for example) or at least have a link to them, because people could come here looking for zodiacs in general. Thylacinus cynocephalus (talk) 03:42, 1 December 2011 (UTC)

Some clarifications on the modifications of the Table of Dates section
I just wanted to mention a few things on my edit of the Table of Dates section, specifically the table itself, on this page.

First off, if anybody can, please confirm the dates of the reference I used with an additional source, especially the sidereal dates, that is, any source besides horoscope.com, that site seems questionable and unprofessional to me. But it seems you search for sidereal zodiac on the internet and it's hard to find anything but the mix-up about Ophiuchus being the "13th sign".

Also I believe some of the labels seemed somewhat crowded with information available elsewhere (for instance, "IAU constellation boundaries (2011)" is redundant when you have another label "Constellation" right above it). I thought it would look a bit cleaner without that redundant or unnecessary information (Jyotisha may be necessary, but the link is available elsewhere on the page under a more recognizable name).

Isangaft220 (talk) 15:15, 22 February 2012 (UTC)
 * In 2003 the label was called Actual Astronomical Dates --Regards, Necessary Evil (talk) 16:22, 22 February 2012 (UTC)


 * Since you are most concerned with the sidereal dates, have you located a good definition of the sidereal signs and/or dates. If an authoritative definition can be found, any number of astronomical books and computer programs can be used to find the dates. Jc3s5h (talk) 16:29, 22 February 2012 (UTC)

Table of dates
1. Is there any official reference to such dates? 2. The reference to "IAU boundaries (2011)": Astronomical Almanac Online!(subscribers) U.S. Naval Observatory 2008 is not available as of this time. --Regards, 125.33.240.149 (talk) 21:42, 15 August 2012 (UTC)

Taking question 2 first, I seriously doubt the U.S. Naval Observatory will be providing dates when the Sun leaves and enters various constellations, because this is not a matter of much interest to astronomers. Maybe some expert with the Wayback Machine actually supported the claimed date at the time the citation was written.

There is no exact set of dates that can be used. The reasons, in order of significance, are


 * Time zones. The Sun moves from one sign or constellation to the next at the same instant throughout the world (ignoring some minor points like parallax and Einstein's theory of relativity). But this instant will have different dates in different parts of the world.


 * Leap year. Roughly speaking, astronomical events that occur at a fixed time in a tropical year tend to be one calendar day earlier shortly after a leap day, compared to their calendar date three years later.


 * Minor variations in the Earth's orbit due to the gravitation influence of the Moon and other planets.

So to be accurate and useful to a world-wide audience, it would be necessary to give the dates in some form of Universal Time and to recompute the dates each year.

The astronomy community is quite well organized, and it is easy to find sources that closely agree with each other and are more-or-less official. So far as I know, the astrology community is not well organized and nothing even approaches being quasi-official. Jc3s5h (talk) 22:38, 15 August 2012 (UTC)


 * After using the Wayback Machine (which turned out to be more intuitive than I expected) I'm convinced the citation to the Astronomical Almanac looked the same in 2010 as it does now. Essentially it means you could, with a great deal of effort, use the Sun chapter of the Astronomical Almanac (which is published each year) to figure out when the Sun was in each constellation. I have several annual issues of that almanac and I can assure you the information is not directly available; it would require hours of calculation. Therefore I will remove that citation. Jc3s5h (talk) 22:48, 15 August 2012 (UTC)

About the template "Template:Zodiac date IAU"
Template_talk:Zodiac_date This section is a soft redirect.

About the template "Template:Zodiac date IAU":

1. 25.5 + 38.2 + 29.3 + 21.1 + 36.9 + 44.5 + 21.1 + 8.4 + 18.4 + 33.6 + 27.4 + 23.9 + 37.7 = 366.0

Why isn't it 365.2425?

2. What's the meaning of constant value 365.25636?

Why isn't it 365.2425 + 365.2425 / 25772 ≈ 365.256672?

3. Are the following results of the template calls all correct?

2005: 18 April – 14 May

2006: 18 April – 14 May

2007: 19 April – 14 May

2008: 18 April – 13 May

2009: 18 April – 14 May

2010: 19 April – 14 May

2011: 19 April – 14 May

2012: 18 April – 14 May

--Regards, 124.64.219.129 (talk) 11:40, 4 September 2012 (UTC)

I suggest that this discussion should take place at Template talk:Zodiac date.

Also, there is User:Jc3s5h, who (a) tagged the talkpage of the subtemplate Zodiac date IAU for references and then (b) came to my talkpage threatening deletion of the template if I didn't "cite my sources". WTH? If the template isn't accurate enough for you, either stop using it or improve it. Don't delete a template doing astronomical calculations because it doesn't have 100% accuracy. Also, don't use unreferenced on talkpages. I will be happy to see the template removed from use in article space pending discussion or improvement, and I am happy to discuss what it does at Template talk:Zodiac date, but not in the Jc3s5h spirit of deletionist ultimatums.

I estimated that the accuracy of the template was going to be about 3 hours. This isn't, strictly speaking, good enough, because it means it will get the date wrong about 3/24 or about one time in eight. So yeah, there is definitely a point in not using it pending improvement. This doesn't mean it should be deleted. --dab (𒁳) 10:03, 5 September 2012 (UTC)

Note: I have removed the template. This is a content issue and not something we helpers can help with (we only deal with problems on editing Wikipedia). Anyway, the discussion is already underway, the template is not necessary. Cheers. -- O BSIDIAN  †  S OUL  10:18, 5 September 2012 (UTC)


 * I will do as Dbachmann suggests and discuss this at Template talk:Zodiac date. Jc3s5h (talk) 12:54, 5 September 2012 (UTC)

Popular mnemonic "The ram, the bull, the heavenly twins..." can be sung to help with memorization.
I don't edit often. Looking for input from those that do edit often. I feel that my edit was valid, and it was quickly removed.

I added this fact, along with a link to an mp3 of the song being sung to show how easy it is to learn. (My daughters and my nephews have all learned it very easily, and can now stand outside singing this song and recognize the signs of the zodiac that are above the horizon). It was removed, with the remover listing it as "spam", and saying that it doesn't work with that tune.

I had read this mnemonic in the book Space (by Michener)long ago, and looked it up online quite a bit, and still found it difficult to learn. I found only one reference to it oringially being sung as a sort of nursery rhyme for babies and small children, and then sang it to this, with slight modification to the words that are listed here on Wikipedia. (Who's to say that the version listed here is the only version).

Although the person who removed this apparently doesn't like it, I do feel that the fact that this can be sung--and I think was originally sung--does indeed add to the understanding of mnemonics in relation to the zodiac, and greatly increases the odds of someone actually learning the zodiac based on any of the mnemonics listed on this wikipedia page.

I don't edit often, so I'll leave it to the regular editors to consider. But I think it defeats the purpose of wikipedia if my input can be so easily discarded, although it did add to the usefulness of this section of the page.

Here is an mp3 sung version of the mnemonic:

http://tinyvox.com/voxes/f8/37/f837bcc37c0dee485664d547f142bf42.mp3 — Preceding unsigned comment added by Alfranco584 (talk • contribs) 17:48, 12 October 2012 (UTC)

What did you know before then?
I did read the references, but not quite sure you understand the differences between astrology and astronomy. Newton may have introduced us to the galaxies and such, but astrology never changes. Astronomy implies that everything is moving. Technically it is, but there are some things that never change. A relative point is always relative to one object, and since there are no known fixed objects, we have to assume that everything is relative. Is there a fixed point? No one knows. I'm sure there might be some people who think they know, but they will always be guessing. Stuffed tiger (talk) 15:44, 5 November 2012 (UTC)


 * Astrology does indeed change. The positions of the Sun, Moon and planets in modern astrology are calculated using Newton's law of universal gravitation and Einstein's general theory of relativity. See for example the ephemerides listed in the astrology shop of the American Federation of Astrologers. Modern Western astrology is tropical, meaning that the vernal equinox, the starting point of the zodiac, moves relative to the fixed stars. This "precession of the equinoxes" is regarded by modern astrologers as exactly the same as modern astronomy's "general precession", which is composed of a major component named the "precession of the equator" (formerly "lunisolar precession") and a component 100 times smaller named the "precession of the ecliptic" (formerly "planetary precessiomn"). Although modern astronomy (and astrology) has no fixed point, it does have inertial space, defined by the positions of many extragalactic radio sources which have no observed motion across the celestial sphere, which is sufficient for modern astronomy. As soon as the planets Uranus, Neptune and Pluto were discovered, they were given symbols similar to the calssical planetary symbols and their influence on the affaire of people were described, generally based on the equivalent gods, another change in astrology. — Joe Kress (talk) 23:54, 6 November 2012 (UTC)