Skyscript Astrology Forum

Hello,

At mark's suggestion, I repost a question I had post in the Philisophy and Science Forum, with Therese Hamilton answer:

carriere.francois wrote:Hello,

I am looking for the moment when the Sassanian passed from a sidereal Helleno-Sassanian zodiac to a tropical zodiac. Early writings (Masha'Allah or Abu'Mashar, as translated by Dr Benjamin Dykes in Persian Nativities I-III) seem to show it was based on sidereal zodiac. About al-Qabisi, I can't tell. In any case the reference was the star zeta Piscium. James Holden (A History of Horoscopic Astrology) seems to have same opinion. Perhaps I think it was around the 9th or 10th century and because sidereal tables (the "zij") may have not been available anymore. Am I correct? Maybe Martin Gansten will want to briefly comment on this issue?

Therese Hamilton wrote:I had this exact same question. When I looked into this question a while ago, I think I came to the conclusion that the change-over began during Al-Qabisi's time period since Masha'Allah was clear in using a sidereal zodiac. (Persian Nativities I, p. 16) Of course if we had the dates when specific tables were introduced we would have our answer. I'll see if I can find my notes on this and post my findings a little later.

As my name has come up, let me say at once that I don't know the exact answer to this question, but my impression is that it was a process rather than a moment in history. In any case, it was later than many seem to think! I'm fairly sure that Rob Hand mentions somewhere (in a PH or possibly ARHAT publication) that some charts include both tropical and sidereal positions (indicating that different kinds of tables were used), but I couldn't say where; it's been too long since I read it.

I had expected Pingree to discuss this, but, as I have searchable PDFs of several of his books and articles, I just did a quick search (for 'sidereal' and 'tropical') and came up with nothing -- not even in his From Astral Omens to Astrology. This was so surprising that I have to wonder if he was shirking the issue for some reason (perhaps it is just very hard to determine). But it may be that I just haven't looked in the right places.

A few references worth following up on this issue:

1. Raymond Mercier's 65 page article/booklet "Studies in the medieval concept of precession" which is cited by Juan Revilla. However, I have been unable to find any reference to this text anywhere on the internet. Instead I have found a text by Raymond Mercier ''Studies on the Transmission of Medieval Mathematical Astronomy'' 2004 – Routledge. This may be a later update to this earlier work and is 334 pages long. So I am assuming Mercier's earlier work is incorporated here.

https://www.routledge.com/Studies-on-th ... 0860789499

2. David Pingree's article: ''The Greek influence in early Islamic mathematical astronomy'', Journal of the American Oriental Society, 93: 32-43, 1973.

3. James Holden's ''"A History of Horoscopic Astrology". The section on Arabian astrology is reproduced on the CURA site. I have placed a link below:

http://cura.free.fr/xxv/23hold1.html

This link below is to a forum piece by the Costa Rican astrologer Juan Revilla which helpfully covers these and some other sources discussing the foundational chart for the city of Baghdad in 762 CE.

http://expreso.co.cr/centaurs/posts/mun ... ghdad.html

Juan Revilla points out these early Perso-Arabic horoscopes seem to be using sidereal tables for planetary longitudes but the tropical positions for the houses.

This may seem initially paradoxical but when you consider the culturally eclectic astronomical sources the early Islamic Caliphate was relying on this is not so bizarre. The sidereal astronomical tables for planetary positions no doubt came from Persian sources and were bolstered by Indian thinking. The use of tropical positions is quite possibly an adaption of Ptolemy's Handy Tables.

The real question though was what were these astrologers thinking? Were they aware of these contradictions? If not it suggests they were not aware of precession at this point. So their astrology cannot be described as a conscious selection of a sidereal or tropical zodiac since they were probably unaware of the distinction at this point.

From what I have read it seems Islamic astronomy made great strides in the 9th century and superceded the Greek, Indian or Persian traditions. At this point it moved from being purely derivative to genuinely innovative.

https://en.wikipedia.org/wiki/Astronomy ... amic_world

https://www.astronomyclub.xyz/theory-re ... ology.html

Mark

given that nuroz is celebrated with the vernal equinox, the ancient (pre-sassanian) iranians seem to be of the solar dynasty to cop a concept i believe is in the puranas ... rather than lunar dynasty qua vedic

Hello,

I am looking for the moment when the Sassanian passed from a sidereal Helleno-Sassanian zodiac to a tropical zodiac. Early writings (Masha'Allah or Abu'Mashar, as translated by Dr Benjamin Dykes in Persian Nativities I-III) seem to show it was based on sidereal zodiac. About al-Qabisi, I can't tell. In any case the reference was the star zeta Piscium. James Holden (A History of Horoscopic Astrology) seems to have same opinion. Perhaps I think it was around the 9th or 10th century and because sidereal tables (the "zij") may have not been available anymore. Am I correct? Maybe Martin Gansten will want to briefly comment on this issue?

The change from sidereal to the tropical zodiac has become fact during the reign of caliph al-Mamun or circa 830 CE. This fact is attested in the Mumtahan zij or Verified zij-the first Arabic zij in the tropical frame of reference. There is a long story behind this change which I have clarified in details in my article "Mumtahan zij- a turning point from sidereal to tropical solar return", published at the moment only in Italian.
But as Martin Gansten correctly notes, this was not a moment but a process. Especially in the west part of the Caliphate, I mean mainly regions of Maghreb and Al-Andalus the sidereal tradition survives until the end of XIII Century mainly on the basis of al-Khwarizmi's zij which was prepared in sidereal frame of reference.

Thank you Astroart. This is exactly the kind of information we've been looking for. We hope to see your article in English soon! From the dating you gave, the tradition was entirely sidereal when Masha'Allah was alive (d. 815), but the tropical zij was introduced during Abu'Ma'shar's time.

The process of conversion to the tropical zij no doubt took some years when there might have been confusion in using tropical and sidereal tables. We would need to study horoscopes from the transition period to ascertain the zodiac(s) being used during that time period.

Meanwhile, for those of us who want to practise our Italian: is the article available online?

Here is the Italian on-line version of my paper:

http://www.apotelesma.it/wp-content/upl ... uharov.pdf

For those who can't read Italian the link below might be informative. A while ago I did an Internet search and found this paper. But the 97 pages wouldn't load easily on my old computer.

http://www.ub.edu/arab/suhayl/volums/vo ... er%201.pdf

"Astronomical Handbooks and Tables from the Islamic World" (750-1900)

Many thanks to both of you!