Zodiac: from Sidereal Sassanian to Tropical zodiac

1
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?
Regards,
François CARRIÈRE

2
carriere.francois wrote:
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?
As this question is historical and concerns a change in technique I would suggest you repost this in the Traditional forum. I think your more likely to get responses there too.

regards,

Mark
As thou conversest with the heavens, so instruct and inform thy minde according to the image of Divinity William Lilly

3
carriere.francois wrote:
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.
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.
http://www.snowcrest.net/sunrise/LostZodiac.htm