At the Astrological Lodge on May 16th 2022, as part of my talk on The Age of Pisces, I addressed in passing the issue of precession in tropical zodiac transits. Equinoctial precession is not an abstract measure, but accrues in real time, at 1° approximately every 72 years (71.6, since we're being fussy). So by this age, our tropical transits are an accumulated one degree in error. Robert Hand deals with this point in the Introduction to his classic Western work, Planets in Transit, and recommends doing the precessional correction then converting the chart back to the Tropical zodiac, which seems rather a rigmarole. Much simpler is to use the Sidereal Zodiac as default, where the whole matter does not arise: to be clear - you do not have to precession-correct SZ transits.
A slow-moving planet like Pluto can take up to a year to shift only one degree in longitude, and even by aged 36, precession can make an appreciable difference in exact outer-planet timing. In mundane forecasting, of course – the charts of nations - the cycles are much longer and the accrued error much greater. Take the USA’s Pluto Return, for example, which Club Tropicana are celebrating in 2022. Now, Pluto’s orbital period is 248 years (247.9 to be precise), and the USA was born July 4th 1776, which by my maths is only 246 years – the USA’s actual sidereal Pluto return arrives in February 2024. Astrologically speaking, whatever is purported to have occurred in America under this transit in 2022 will be nothing compared to what happens in two years time.
Sidereal conjunction of Neptune to England's natal Moon
The error is of course cumulative. Take Neptune’s orbital period of 164 years, which at one degree per 72 years accrues approximately 2.5 degrees of precession per cycle. Neptune's orbital motion also happens to be around 2.5 degrees per year, so its each successive tropical circuit is one degree in error. In a very old chart, like for example, England’s national horoscope of December 25th 1066, which has had six Neptune conjunctions to its Moon in Pisces in nearly a thousand years, the error by now is six years. Sure enough, England’s next tropical Neptune-Moon conjunction of May 5th 2024 is actually exact on May 19th 2030. For a technique like a Tropical Solar Return, the symbolic difference is even more dramatic. One degree per 72 years equates an error of a whole day in your Sun’s return chart when you reach this age. Even by aged 36 this equates to half a day or 12 hours; by aged 18 it is six hours, and by aged six it is two hours in error – already enough to give a wrong ascendant. No wonder Solar Returns are such an integral part of Western Sidereal Astrology. There is no getting around this. You have to factor in precession to your coordinates when sky-watching, otherwise the object you are looking for simply won’t be there. One degree every seventy-two years gives 25,920 for the entire 360 degree cycle, a period known as the Great Year. Graham Hancock's bestselling book Fingerprints of the Gods, incidentally, explores this astronomical phenomenon in depth, and he references key numbers in the Great Year (12, 72, 2160, 4320 and their multiples) which he suggests are baked into comparative world myths: Mayan, Norse, Egyptian, Vedic, etc. According to the official record, Hipparchus of Rhodes discovered precession c.150 BC, and gave its value at approximately one degree every hundred years. A genius breakthrough for its time, but what Hancock and others say is that the Great Year was already a known world archetype, and a much more accurate figure of a degree every 72 years was common scholarly knowledge. This goes beyond symbolic hair-splitting and shows the Sidereal Zodiac is not simply a matter of whether one is Taurus or Gemini. There is a real issue of timing accuracy, where the familiar Tropical zodiac most Western astrologers use is in error. Vedic astrology is explicitly Sidereal, but Western Astrology was also originally grounded in this star-based system, and I hope a movement back to it is underway.