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Deb, did you try the DeLuce option for the traditional Baghdad date and time? (July 31, 762, 2:40 p.m. or thereabouts) The DeLuce ayanamsa is often called the zeta Piscium value, but I can't test it as I don't have that option that works. I do have an Indian program I can try later, but I haven't really learned that program yet.

There are a few internet sites that can help with ayanamsa options. I'll try to look them up a bit later. I'm also writing a post, but don't know when it will be finished. As always, Martin is helpful with his posts. I do plan to reply to the post you wrote yesterday.
http://www.snowcrest.net/sunrise/LostZodiac.htm

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I finally figured out why the ayanamsa question involving the zeta Piscium zodiac has been driving me crazy. The current ayanamsa value given in software must be based on an erroneous and much too high precessional rate, unless there is some other computational method or error that I don't understand. (Is anyone in touch with Juan Revilla, astrology's astronomical expert?)

EDITING NOTE, December 28:

I have since discovered that the DeLuce ayanamsa has no relationship to zeta Piscium, although someone has given it that name. DeLuce states in his book that the ayanamsa he uses is based on the birth of Christ. So the software value is likely correct for that date (as per DeLuce's dating).
Last edited by Therese Hamilton on Sat Dec 28, 2013 11:05 pm, edited 2 times in total.
http://www.snowcrest.net/sunrise/LostZodiac.htm

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A Very Brief History of the Most Popular Sidereal Zodiacs

221 AD: Based on statements by academic scholars Cyril Fagan decides that 15? of Taurus and Scorpio are the correct historical Egyptian longitudes for Aldebaran and Antares respectively. This places the zero date when the tropical and sidereal zodiacs coincided at 221 AD. This zodiac has become known as the Fagan-Allen zodiac because Garth Allen (Donald Bradley) adjusted Fagan's original value by 6 minutes based on the results of his own research. Let's say that at this time the longitude of the Sun on a particular date is 6? of Leo.

285 AD: In 1956 the Indian government decides it has to do something about the disastrous multiple calendars used throughout India. Each district has its favored dates for religious celebrations. A committee is formed headed by N.C. Lahiri. This committee chooses Spica at 180? as 0?Libra. The point opposite is zero Aries. Due to accrued precession between 221 and 285, the Sun is located at 6?53' Leo. So the difference between longitudes in the Fagan zodiac and Lahiri will always be 53 minutes for any date and for any planet or house cusp.

291 AD: K.S. Krishnamurti conducts extensive research and study of horary charts. He concludes that the Lahiri zodiac must be adjusted by 6 minutes (approximate...there is a precise value) So the Sun is now at 6?59' Leo due to the accrued precession between 285 and 291.

397 AD: Ayanamsa used by B. V. Raman and his followers. The tables that produce this zero date may be a conscious adjustment or accidental change from the zeta Piscium (Zij) tables. These tables were apparently used by Raman's grandfather and Swami Sri Yukteswar, who were contemporaries. There is no record of the origin of these tables, but they are the closest to the zeta Piscium zodiac. The Sun in Leo has now "progressed" from 6? 59' (Krishnamurti) to 8? 20' Leo, the difference between Krishnamurti and Raman being 1? 21'.

564 AD: A historical event. Sassanian astronomers decide that in this year zeta Piscium is the zero position for their reformed Zij tables. We can see that due to the progression of years from 291 to 564, the Sun's longitude has progressed even further into Leo from the Indian government or Raman positions. There are no existing Zij tables, but Kennedy and Pingree believe they have reconstructed these values according to parameters they chose in Masha'allah's Astrological History. (This zero date is discussed on the Swiss Ephemeris site where all the ayanamsas are outlined.)

In my opinion it's possible that these tables never were precise or entirely correct for all the planets. I suspect they disappeared rather quickly when tropical tables became available. This was sometime (perhaps shortly after) Masha'allah's death. There must have been a period of confusion as astrologers began to use he newly available tropical tables. No doubt horoscopes probably contained both tropical and Zij longitudes until the Zij tables disappeared.

We can calculate the true longitudes in exact degrees and minutes as correct Zij tables would have placed them because we have the precise position of zeta Piscium in longitude. From any known ayanamsa zero date (zodiac), we can convert any longitude to the zeta Piscium zodiac. So the conversion of Krishnamurti to zeta Piscium is 3? 53' because in that zodiac zeta Piscium is located at 26? 07' Pisces.

We add the difference (3? 53') between that longitude and zero degrees in the zeta Piscium zodiac. This same conversion would be used for any year for any planetary longitude. If we were converting from the Raman zodiac we would add 2? 32' because the Raman zero year is closer to the zeta Piscium year than Krishnamurti.

All the other ayanamsas listed in astrological software, in books or on-line were chosen by individuals, each of whom felt that ayanamsa value gave the best results in actual astrological work or in theory. (The so-called Yukteswar zodiac was never intended for astrology as it's based on a theoretical date in Indian cosmology. In practice Sri Yukteswar seems to have used the same tables as Raman's grandfather as noted in an ayanamsa value given in The Holy Science.)
Last edited by Therese Hamilton on Sat Dec 28, 2013 6:15 am, edited 6 times in total.
http://www.snowcrest.net/sunrise/LostZodiac.htm

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Martin wrote:
The way I see it, there are just two basic alternatives: either the zodiac is fixed in relation to the constellations (sidereal) or fixed in relation to the seasons (tropical). Within either option, you then need to decide where to locate the starting point (because a circle has no beginning).
This is the way I see it as well. Although there are a number of so-called "sidereal" zodiacs, my personal opinion is that if the sidereal zodiac is a valid entity, there is only ONE such zodiac. I believe we're in the ball park with the Lahiri and Krishnamurti values. Those who use one of those zodiacs can use the varga (divisional) charts such as the navamsa to attempt to zero in on a suggested zero point. With computers we should be able to come very close to a correct starting point, but astrologers as a group are more interested in clients than research.
Historically, it is true that only one tropical zodiac has been in much use, namely, the one that equates the vernal equinox with 0? Aries -- no doubt because this zodiac came into use at a time when the vernal equinox was very near the beginning of the constellation Aries anyway. But some have argued for, and experimented with, a reverse tropical zodiac for the southern hemisphere (taking the northern autumnal equinox as 0? Aries), and other theoretical positions are possible.

If I still used the tropical zodiac, I'd be quite troubled by the hemisphere dichotomy and the seasonal definitions of the signs that apply only in the northern hemisphere. This seems to be an area that astrologers shy away from discussing. This may be the biggest theoretical reason to question the validity of the tropical zodiac for astrologers. I can see why the precise measurement of the tropical zodiac would be attractive and necessary to astronomers, however.
http://www.snowcrest.net/sunrise/LostZodiac.htm

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Deb wrote:
Getting back to the planet positions suggested now, I think this is very convincing in coming closer to the historically recorded positions than anything else I've seen. The table below shows Albiruni's reported figures, alongside the modern computations of Tuckerman (reported by Pingree and Allawi) and then the ones reported by Therese. If we add the 3?53 to the ascendant of the earlier chart it brings the ascendant to 5?11 Sagittarius, so makes a perfect fit with the historical references Allawi reports (p.63) that the ascendant is in the 246th degree of absolute longitude, and there are 117 degrees between the ascendant and the Sun, to reflect the distance between the "'face of Baghdad' and the azimuth of Mecca."
Quite a useful table, Deb. Thank you. It's exciting to see the values come together to align with historical reference. There is, of course the option of adjusting the ascendant slightly by changing the time. I have only followed James Holden's chosen time of 2:40 pm. I would probably adjust the time slightly myself to move the ascendant more comfortably into the 246th degree. (Is the 246th degree 5+ or 6+? I don't know.)

Right now the corrected ascendant is 6? 01' (rather than 5? 11') I get a 1 minute difference for Mars (4? 16') and a few minutes difference for Rahu (N. Node), both negligible. I have this nifty Texas Instruments 59 programmable calculator (courtesy of my husband) from the days before computers that will add, subtract, multiply or divide degrees and minutes in a second or two. Love it!
http://www.snowcrest.net/sunrise/LostZodiac.htm

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Martin wrote:
I think it was DeLuce who based his value on the assumption that the vernal equinox ought to have entered sidereal Pisces around the birth of Jesus...
This is correct! I just checked DeLuce. I wonder how the DeLuce ayanamsa came to be called the zeta Piscium ayanamsa?! Now I understand why that ayanamsa has such an extreme value. So this value in astrology software is probably correct if dated from the time of Christ.

According to DeLuce, there's a reason for the confusion over the ayanamsa:

"In India today there is disagreement among astrologers as to the date of zero ayanamsa. Presumably for religious and metaphysical reasons it has been hidden in order to exclude those who are not properly initiated to possess this essential key to the vital secrets of scientific astrology." Robert De Luce, Constellational Astrology (1963), p. 4.

Ah, the spiritual philosophy of the 1960s!

The great thing about being an astrologer: We're always learning something new...
http://www.snowcrest.net/sunrise/LostZodiac.htm

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Thanks for pointing me in the right direction Martin, and thank you Pankajudbey, for adding those links with detailed information. I've read through most of the first two links, so a lot has sunken in, but I think I need to stop and digest for now, otherwise I'll lose what I've just absorbed :) These are great resources to return to - I couldn't get the third link to open though.

Therese - I don't think I could have followed much of the information in those links had I not read your subsequent posts and your "brief history" first. If I can persuade you - please consider developing this a little and publishing it as an article that explains the issues for novices. I would certainly have a place for it here on Skyscript, though I'm sure there are many magazines and journals that would want to publish something that gives a valuable and necessary overview of the complicated issues, in a way that is so easy to understand.
Therese wrote:Is anyone in touch with Juan Revilla, astrology's astronomical expert?
Juan is a member of the forum although its been about 6 months since he last posted - I've just sent him an email and PM to let him know about this thread and your concern about a computational error in software.
Therese wrote:Deb, did you try the DeLuce option for the traditional Baghdad date and time? (July 31, 762, 2:40 p.m. or thereabouts) The DeLuce ayanamsa is often called the zeta Piscium value, but I can't test it as I don't have that option that works. I do have an Indian program I can try later, but I haven't really learned that program yet.
I did, but the positions generated seem to be way off. Here is a link to the chart so you can view it:

http://skyscript.co.uk/im/Baghdad_Deluce.gif

I wanted to make some more comments but there's too much going on family-wise at the moment, so I'll post this for now and come back later.

Thanks again for the explanations!

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Deb wrote:Thanks for pointing me in the right direction Martin, and thank you Pankajudbey, for adding those links with detailed information. I've read through most of the first two links, so a lot has sunken in, but I think I need to stop and digest for now, otherwise I'll lose what I've just absorbed :) These are great resources to return to - I couldn't get the third link to open though.
Indeed, many thanks to Pankaj for the links. The Digital Library of India is a wonderful resource, but the Internet connection can be a bit erratic. I'm sending you the article (from Indian Journal of History of Science) by email, Deb.
https://astrology.martingansten.com/

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These positions are for Surya Siddhanta Ayanamsha with the calculations based on the routines of Surya Siddhanta with a bit of modern fiddling.(Jagannath Hora)
Image
Sun in sidereal Leo trine to Jupiter in Sagittarius conj the cusp of ascendant(within 5 deg).The position of heavvies like Saturn and Mars are significantly ,whereas Mercury and Venus are not that different than DeLuce version.
Image
PD

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Therese Hamilton wrote:
Martin wrote:
Indeed, many thanks to Pankaj for the links. The Digital Library of India is a wonderful resource, but the Internet connection can be a bit erratic. I'm sending you the article (from Indian Journal of History of Science) by email, Deb.
Could you also send the article to me, Martin? I could not get the link to open. Use my eastwest9 email address. Thank you.

Therese
Try this one
http://www.dli.gov.in/rawdataupload/upl ... 60_257.pdf

I think it is the same