Tropical and Sidereal - the plot thickens!

I usually skim over any mention of sidereal astrology. I knew only that sidereal (Vedic) is the system of astrology used in India, and that the zodiac signs relate to a slightly different period - a variance of almost one full sign, when compared with the tropical zodiac.

I was inspired to try to discover more.

After a session of searching the internet, I've found out that the difference between sidereal and tropical is mainly in the calculation of the starting point of the zodiac.

In Western/tropical astrology the calculation of the Sun passing through the 1st degree of Aries is marked by the Spring equinox or March 21st. By extension, if one looks in a Western ephemeris it is clear that the beginning of each season is lined up with the Sun passing into each of the cardinal signs in the zodiac – Aries, Cancer, Libra, and Capricorn. The tropical zodiac, therefore, is a symbolic system based on the Sun/Earth relationship and is oriented to the seasons.

In sidereal astrology the calculation of the Sun passing through the 1st degree of Aries is marked by the Sun passing through the actual observable fixed stars making up the constellation Aries and has nothing to do with the seasons. “Sider” means “star” and therefore sidereal astrology is based on the actual astronomical positions of the planets against the backdrop of the fixed star constellations. The sidereal zodiac is not symbolic but is oriented to an observable phenomenon.

Once upon a time, around 285AD the two systems were in harmony, and gradually ever since then the two have slowly moved apart due to the precession of the equinox.

Precession of the Equinox is the age old phenomenon whereby an observer on Earth will notice that after one year, he will not realign with the exact same point in inertial space. In ancient times observers on Earth noticed that the vernal equinox aligned with the constellation Aries, then after a few thousand years with constellation Pisces. Now as many know, we are at the "dawning of the age of Aquarius." This backward procession is the precession of the equinox – whereby the equinoctial point slowly recedes through the 12 constellations of the Zodiac, completing a full cycle in around 26,000 years.

So.....which is the more accurate system for use in trying to assess human personality from an astrological chart of the time of their birth - Sun based, or Star based? "Suck it and see!" Try both and decide which works.

I understand that the differences in the two systems are more extensive that described above. Apparently in Vedic/sidereal astrology a lot of emphasis is placed on the Moon's position, and the Sun is less important. Other subtle differences in interpretation exist too.
It's not possible to do a "straight swap", by simply moving the position of natal planets to allign with the sidereal system, and use tropical interpretations. Or so it appears to me.

Even if we did make a "straight swap", the overall flavour of the chart would remain very similar. What would happen is this. Any planet at less than 24* of a sign would move into the previous sign. 24* is the current approximate difference in calculation between the two systems... this has to be approximate because there is argument about this too ! The amount difference in longitude in the two methods of calculation is known as the ayanamsa, by the way.

An easy way to do the swap-over in your head: if the planet’s degrees are less than 24 in any given sign, add 6 degrees and go back a sign. For example, if a planet is at 11 degrees Gemini then add 6 degrees and go back to Taurus. The Sidereal position would be 17 degrees Taurus. I've looked at my own chart with this in mind.

My Aquarian Sun would move into sidereal Capricorn, but Jupiter in tropical Pisces would take the Sun's place in sidereal Aquarius. Mercury in Capricorn would move into sidereal Sagittarius, Venus in Sagittarius would go to sidereal Scorpio, and so on. I have only one planet in my chart which would remain in the same sign - Mars at almost 29 Scorpio would stay there, giving me Venus at one end of Scorpio and Mars at the other end. My Aries Moon would become a sidereal Pisces Moon, Saturn likewise into Pisces. Uranus from Taurus to Aries. Neptune from Virgo to Leo, Pluto from Leo to Cancer.

Nothing so far would lead me to think that one system is more accurate than the other.
I could make a case for either, there is no glaring inaccuracy. Perhaps Mercury in Sagittarius is not quite "me" , though !

A person with a "bundle" pattern in their chart - all planets grouped in 3 or 4 signs, or even a strong stellium, might be able to asses the difference in systems with more accuracy than I am able to do.

The really glaring difference for me, would be my ascendant moving from Cancer to Gemini. Definitely inaccurate. However, my birth time could still be out by up to an hour or maybe more. I used to think I had Leo rising some years ago. Stories of my birth time varied as told by Dad, Mum, and Auntie! Dad said "teatime", Auntie said "about half past two", Mum was in no state to know, but thought "around 3 o'clock." A professional astrologer has rectified the time using details of events in my life, and came up with 2.27pm as the nearest degree he could be sure of - but he said that for sure my ascendant is Cancer.

If my birthtime had given me an ascendant just into Leo, that would fit, because sidereally it would be in Cancer, which I consider to be correct.

In my own case, then, it would all come down to time of birth. If an accurate time of birth gave me a Leo ascendant, I'd say sidereal fit me better. If an accurate birthtime gave me Cancer ascendant in tropical, then definitely tropical is the better fit. So.... as it stands at present, tropical works best for me.