Martin Gansten wrote: Wed May 14, 2025 3:26 pm
If you have been following my work, you may have read the book that the title of this thread refers to, in which I mention my objections to the term 'western astrology'. In my opinion there is no western tradition of astrology, in any meaningful sense, until the early modern period. The astrology that I do would have seemed quite familiar to a medieval Persian astrologer, but that style in itself contains elements derived both from India and directly from the Hellenistic world. There are no 'pure' astrological lineages, nor any real east/west divide; rather, as Pingree said, the transmission of astrology progressed 'in appropriate circles'.
It's been quite a few years since I read the book that the title of this thread refers to. ; )
This deserves a topic all its own, but I will be brief.
All intellectual traditions are, of course, products of cross-cultural exchange, and no lineage is ever “pure.” Yet by recognizing Western astrology as a historically identifiable tradition. We trace a thread: from Alexandria’s synthesis of Babylonian, Egyptian, and Greek thought; through Persian and Arabic custodianship in the early medieval period; into the Latin-language translations that fueled university curricula and courtly practice after the 12th century; onward through Renaissance printing houses where astrological treatises proliferated. Though fragmented in the modern era, that thread still continues and, one might say, has a strand or two added due to the rediscovery of ancient texts. Acknowledging this cumbersome continuum reminds us that today’s astrology—as eclectic as it is—has been a conversation nearly two millennia old, one that has continually adapted while preserving its foundational core: signs, planets, and houses.
Martin Gansten wrote: Wed May 14, 2025 3:26 pm
In my opinion, the ayanāṃśa question can't be divorced from the overall calculation of planetary longitudes, where we all (presumably) use modern values rather than, say, the
Perpetual Tables or a medieval
zīj. I vaguely recalled an old but interesting paper by Therese Hamilton where she found modern recalculation of longitudes with the Krishnamurti ayanāṃśa often to be the best match for longitudes given in Babylonian tablets, and after some searching I found it
here. If memory serves, I have also seen a similar comparison (by Therese or someone else) based on early Arabic-language charts, perhaps from Māshāʾallāh. Sorry to be so vague, but this is just from memory; perhaps someone else knows what I mean and can give the reference.
It's hard to tell if it's a similar comparison, but that's why I mentioned Raymond Mercier in my prior post. He concludes that multiple ancient astronomical traditions—Greek, Indian, Persian, and Arabic—converged on a sidereal zero point located just east of Zeta Piscium, likely originating with Hipparchus.
This is a topic that truly deserves its own discussion too, but I’ll try to keep things concise—though it may warrant deeper treatment at another time.
If the only ephemeris available has already been calculated using a specific ayanāṃśa, then naturally one must work within that framework. For modern times, I must respectfully disagree with the notion that ayanāṃśa is merely a by-product of which ephemeris one uses. Fundamentally, ayanāṃśa is a matter of defining the zero point of the zodiac—it's a question of zodiacal convention, not a computational artifact. Starting from a tropical ephemeris , the ayanāṃśa remains an entirely independent parameter. It specifies how the tropical vernal equinox is projected onto the sidereal framework. Conflating this distinction risks confusing (a) an astronomical data source with (b) a zodiacal calibration method—two fundamentally different layers of analysis.
Setting aside, for the moment, the question of Hellenistic sidereal values, Hamilton’s work suggesting that the Krishnamurti ayanāṃśa aligns closely with the handful of recorded longitudes on five tablets in surviving Babylonian horoscopes is certainly interesting. But this alignment does not settle the matter. While her conclusion may appear pragmatically justified by numerical fit, though clearly unintentional, she inadvertently implies a historical continuity that has not been established. The observational limitations of Babylonian astronomy, combined with the fragmentary nature of the surviving data, make it difficult to draw any definitive conclusions. Moreover, agreement with a few isolated texts does not make the Krishnamurti ayanāṃśa a universal or historically authoritative choice. Within the same context, the Fagan/Bradley fares almost as well, and if more Babylonian horoscopes are uncovered, it may indeed perform as well or better than Krishnamurti ayanamsa.
Any serious effort to understand Babylonian horoscopes must begin with the sidereal framework they actually used—not one retrofitted from later or unrelated traditions. A remarkable convergence of sidereal zero points was proposed independently by F. X. Kugler (c. 1900), later codified by Peter Huber (1958), and further refined by Britton. Fagan’s independent work, along with Bradley’s 1957 adjustments, closely corroborated the positions established by Kugler and Huber. As a side note, Huber’s 1958 publication postdates both Fagan’s 1950 book and Bradley’s refinements, suggesting that his contribution was more a confirmation and formal codification than a source of influence on their earlier determinations. All these sources—Kugler, Huber, Britton, and Fagan/Bradley—indicate a sidereal zero point where Spica (Chitrā) stood at approximately 29° Virgo, offering compelling evidence for a star-based reference system deeply embedded in Mesopotamian astronomical practice.
The Krishnamurti ayanāṃśa, though numerically close to Fagan/Bradley, derives from a variant calibration of Spica’s (Chitrā) position at approximately 30Virgo. While modern astrologers are free to adopt whatever ayanāṃśa best serves their predictive or philosophical needs, historical reconstruction demands a more rigorous standard. When studying ancient systems like Babylonian astrology, we must privilege the internal logic and attested reference points of the original tradition. Only then can we avoid the circularity of validating modern constructs with modern tools—and preserve the interpretive integrity of the sources we seek to understand. Rochberg’s
Babylonian Horoscopes (1998) operates entirely within this framework established by Kugler and Huber.
The Krishnamurti ayanāṃśa has gained popularity within and without its own modern Indian framework—but that success should not be mistaken for historical relevance. Babylonian horoscopy operated under a different sidereal logic, shaped by distinct observational practices, cultural assumptions, and astronomical goals.
Martin Gansten wrote: Wed May 14, 2025 3:26 pm
I don't think there is a value in adhering to ancient (or medieval) astronomical/mathematical models as such. Doing so could land us in some very odd positions (trepidation, anyone?). For instance, Vettius Valens explicitly supports the Babylonian definition of 0° Aries as located 8° prior to the equinox, which he clearly regards as a fixed value. This is neither Ptolemy's tropical zodiac nor a sidereal definition in the modern sense, because Valens didn't understand precession. But I'm not aware of any modern Hellenistic-style astrologers actually using Valens' preferred zodiac when applying his techniques.
First, modern Western sidereal astrology does not rely on ancient or medieval astronomical models per se but instead uses a rigorously reconstructed sidereal framework based on a convergence of derived values by Huber, Britton, and Fagan/Bradley, aligning the zodiac with observable sidereal fixed star positions. The contemporary sidereal zodiac used by Western astrologers—sometimes called the "Fagan-Bradley" or "Western sidereal" system—derives its ayanāṃśa not from any arbitrary tradition
Respectfully, invoking Valens here feels like a non sequitur—it doesn’t advance our conversation. Valens' use of a zodiac starting 8° before the vernal equinox is historically interesting, but it isn't relevant since I was speaking of Mercier's findings. I agree it is ultimately anachronistic for modern use. His conception predates a functional understanding of axial precession and the trepidation model.
So while Valens’ texts are rich in technique, we don’t need to adopt his cosmology wholesale—especially not his zodiacal framework. The sidereal zodiac in modern Western sidereal astrology is anchored in astronomical precision, not in outdated assumptions.