Skyscript Astrology Forum

Thanks to Alexander Jones, we now have the evidence we need for the use of zodiacs from earliest times up until the full tropical conversion in the 5th century. Jones' book is Ptolemy in Perspective (2010) and sells for $219 on Amazon. (Academic publisher, $175 as an ebook) Luckily for astrologers, the chapter on the early use of the zodiac is available on the Internet.

Most of the text is highly mathematical. This chapter is about 30 pages long with 82 extensive references. Jones' research is to date by far the most important zodiac research for astrologers. Here are a few quotes from the chapter "Ancient Rejection and Adoption of Ptolemy's Frame of Reference in Longitudes:"
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QUOTES:
The predominance of sidereal longitudes in the astronomy of the papyri and astrological texts, at least as late as the third century, is not in doubt....(p. 17)

...this is a clear demonstration that Then's formula effectively converts Ptolemy's longitudes to the prevailing sidereal frame of reference...From the first century to the first half of the fourth there are no more than one or two data points that could be interpreted as tropical longitudes, and these are just as likely to be errors. (p. 17)

The graphs show the ambiguity of the situation for the fifth century;...the cluster of data points between A.D. 400 and 500 might appear consistent with Ptolemy's tropical longitudes or sidereal longitudes. (p. 19)

From the combined evidence of the papyri and the astrological texts (especially Vittius Valens) we can see that the astrologers of the first four centuries of our era knew and used a great variety of tables to compute the longitudes of the heavenly bodies and the cardinal points of their horoscopes...Yet there is a broad consistency in the longitudes, whether we look at the long-term pattern exhibited by horoscopes that were computed from unidentified tables, or we look at the parameters built into the extant tables. The longitudes tend to be greater than the ostensibly tropical longitudes yielded by Ptolemy's tables....(p. 27)

...it cannot be emphasized too strongly that up to the present we have not seen a single complete horoscope computed for the date before the late fourth century that, taken as a whole, fits Ptolemy's tropical frame of reference better than the common sidereal frame of reference, not a single table other than Ptolemy's that assumes a solar longitudinal period less than 365 1/4 days. (p. 29)

Thus we can see a remarkable discontinuity in the astrologers' practice...after 350, Ptolemy is practically the exclusive resource [tropical], and Theon's forumula [conversion to sidereal] is abandoned. (p. 34)
([.....] mine, T.H.)

The ancient reception of Ptolemy's astronomical tables went in two stages: initial, gradual and limited acceptance during the first two centuries following the Almagest's publication, and an apparently abrupt transition to complete acceptance, to the exclusion of other sets of tables and without adjustment of the frame of reference, during the fourth century. (p. 39)

...when astrology rebounded during the fifth century, the old practices had been swept away..." (p.40)

[That is, tables that produced sidereal longitudes were no longer used. T.H.]

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From the fifth century on western astrologers were tropical, although sidereal calculations survived among the Persians. This is why Benjamin Dykes' translations are so valuable and exciting. Much of that material is carried over from earlier centuries and writers.

Kollerstom's research is discussed in this chapter as well as Valens' calculations.

EDIT: Jones' chapter on the Internet is no longer available, so I have erased the link.

Thanks Therese for posting this, it's fascinating and needs to be better known! Unfortunately the chapter available to "view only" is incomplete, with gaps - but I'm afraid I won't be shelling out $219!
Graham

very interesting therese. thanks! i need someone to condense what the basic jest of this is~!

Graham, I believe I have a PDF of the chapter which used to be on the Internet if you would like it. Yes...checking....my hard copy is 44 pages. But I won't be back at the computer until this evening (in California).

Therese

It's too technical for me too, but I think I understood this much:
It had been thought that the slippage in accuracy of computed planetary positions noted from Ptolemy's time up to mid 4th century was due to astrologers erroneously making an adjustment for movement of the VP because of so-called "trepidation" (supposed oscillation of the VP forwards and back by 8?), but this does not adequately account for the discrepancy with (what would be) correct Ptolemaic tropical values. We can only fully explain the apparent slippage by accepting that the zodiac was generally calculated sidereally up to mid 4th century.
Valens thought the structure of the zodiac was defined by the VP, but didn't know about precession; he made adjustments to the tables he was using to allow for the VP being at 8? Aries (not 0?), where presumably he thought it would be for all time.
I hope someone will correct me if I'm wrong.
Graham

Therese I remember you, Deb, and others discussed this same topic before. I found the link she provided at that time to Google books here:

http://skyscript.co.uk/forums/viewtopic ... s&start=30

For some reason I?m able to see a little more of the chapter you quote via her link than via yours, but not very much so. And this could be an idiosyncrasy of my browser or something. I do thank you for your link.

I also see that Deb cautioned at that time that there was much more to this book than the online excerpt from Google books, and that a fuller reading was essential lest the meaning be potentially distorted. Her full statement is in the link above. Please provide a legal link to the full chapter if you have one! Otherwise I?d have to take Deb?s word that ?The article needs to be read in its entirety because it would be too easy for anyone to cherry pick comments out of the article to give an impression of the matter being far more simplified and conclusive than it really is.?

Thanks,

Phil

Phil wrote: I also see that Deb cautioned at that time that there was much more to this book than the online excerpt from Google books, and that a fuller reading was essential lest the meaning be potentially distorted. Her full statement is in the link above. Please provide a legal link to the full chapter if you have one! Otherwise I?d have to take Deb?s word that ?The article needs to be read in its entirety because it would be too easy for anyone to cherry pick comments out of the article to give an impression of the matter being far more simplified and conclusive than it really is.?

The only link I have is the one I posted which was from an email several months old. There is no doubt whatsoever about Jones' conclusions in that chapter. They are crystal clear, and he provides the math to back up his findings. I have carefully read the chapter several times through, and one cannot argue with his conclusion. 39 pages of text, 5 pages of notes. Please email me if you want more details. eastwest9@snowcrest.net

Using other less stringent methods, Nick Kollerstom reached the same conclusions. His article in full is on the Internet. Do a search for "Kollertrom The Star Zodiac of Antiquity."

Therese

Thanks Therese. Well for now I might defer to Deb, who noted in your last discussion about the exact same topic, last year, that Jones?s paper

??presents a much more complex situation than what could be described as one fundamental sidereal/tropical split.?

And that ?...ultimately it leaves a lot of questions hanging in the air. We end up a lot more informed about what we don't know than what we do know.?

Again, the link to that discussion is above. I?ve ordered the book at my library, as Deb recommended due to the complexity and nuance of the subject. But my email is coming your way. Maybe the chapter is conclusive. Thank you!