When I am thinking about this, one more question comes to my mind: what's the point of the sidereal zodiac then?
The point of the sidereal zodiac is that it works, and the best evidence is to try it out.
Everything I have read about the diferences of the two pointed out that the sidereal zodiac is the real one, because it copies the real sky. That's obviously wrong, as it also ignores the different lengths of the constellations but gets the precession right.
I do not understand the point of your first sentence since both zodiacs happen to use the actual sky. The difference is that the tropical zodiac is based on the seasons, while the sidereal zodiac is based on the constellations. As you noted, the Hellenistic astrologers considered both, either because they were not aware of precession (Valens) or did not matter to them at the time (Ptolemy).
The argument about the length of the constellations is overrated. The fact is that they all fall roughly within their boundaries to the extent that 99% of sidereal astrologers have their zodiacs all within a range of 2-3 degrees compared to the 25 degree difference to the tropical zodiac. (see also -
https://www.astrologyweekly.com/forum/showpost.php?p=876390&postcount=50)
Note that it was recently brought to my attention that the IAU boundaries might have been different from the ancient ones:
''
Thus, if the retrospective search for the location of the vernal point at focuses on the time of Hipparchus, one can hardly resist the suspicion that Hipparchus himself has taken a hand in modifying the constellation outlines to bring this about. For this there is some evidence. Inspection of the zodiacal figurations within their thirty-degree compartments (most conveniently depicted in Bouche-Leclercq 131 ff.) reveals that some displacement of the zodiacal figures has taken place. For example : Cancer’s territory once obviously extended into Gemini, just as on the other side Leo’s head and front paws protrude ten degrees or more into Cancer : the sign’s boundary has been adjusted to secure sb0° as the solstitial point. Exactly the same has happened in respect of Capricorn : no wonder Manilius calls it a cramped constellation, for whilst it has plenty of room to stretch in Sagittarius, it is outrageously elbowed aside by Aquarius ; but an explanation lies to hand if its boundaries have been redrawn to secure V^0° as the autumnal point.'' - Manilius, & Goold, G. P. (1985). Astronomica. BG Teubner.
I personally can see and draw a much larger crab and ram, but that may be just me.
But you mention that you wanted to use it because it more closely follows the hellenistic traditions of the constellations, but then, what about the different lengths and additional constellations that aren't part of it?
The sidereal zodiac is based on twelve constellations on the ecliptic. The reason of 12 x 30 degrees, or the constellations themselves may seem arbitrary, but that is what the Babylonians used - constellations and a sexigesimal system.
First and foremost, the sidereal zodiac is traditional because it originates in antiquity, and was used by everyone in antiquity, it was the original and dominant form of the twelve-fold circle. All Babylonian and most of the Hellenistic astrologers used a sidereal zodiac since they put the equinoxes and solstices either at the 8th, 10th or 15th degree of the images (there was debate about the correct degree since the Sun is difficult to observe relative to the stars).
However there is no mention of a zodiac that begins with the vernal equinox until the astronomer Hipparchus in the 2nd century BC (some astronomers like Apollinarius followed suit, while others like Eudoxus before him had them placed at the middle of the signs). Astrologically, as far as I am aware, a brief mention can be found in Manilius and in a summary of the first century astrologer (court astrologer of Emperor Tiberius and compiler/editor of Plato's works) Thrasyllus, who actually criticizes it: "the tropics are not made at the first degree of a sign, as some maintain, but at the eighth degree."
Here is what recently an academic said about the hundreds of uncovered Hellenistic horoscopes:
''it cannot be emphasized too strongly that up to the present we have not seen a single complete horoscope computed for the date before the late fourth century that, taken as a whole, fits Ptolemy's tropical frame of reference better than the common sidereal frame of reference, not a single table other than Ptolemy's that assumes a solar longitudinal period less than 365 1/4 days.'' - Jones, A. (Ed.). (2009). Ptolemy in perspective: use and criticism of his work from antiquity to the nineteenth century (Vol. 23). Springer Science & Business Media.
Ptolemy's arguments and adoption of the tropical zodiac were not immediately accepted, and people continued to use sidereal tables well into the middle ages. The best counter-argument I got to this was that calculations did not matter, but what mattered was their ''thinking''. Note, that at the time of Ptolemy, the Babylonian zodiac was less than a degree apart from the tropical. Eventually parts of Hellenistic astrology were transmitted to India, and the Indians still use only a sidereal zodiac to this day.
Secondly, it is plausible rather than impossible. If the zodiac was based on the seasons, Cardano and Campanella argued that it should be reversed for the newly inhabited Southern Hemisphere, some traditional astrologers, acolytes of Ptolemy (
http://www.cieloeterra.it/eng/eng.index.html) today also argue for the reversal.
However, reversing all signs (or just the essential dignities and significations) in the Southern Hemisphere does not fix problems at all, it actually brings more (
https://www.timeanddate.com/astronomy/equinox-not-equal.html ), this change can easily necessitate many zodiacs for different latitudes -
https://books.google.bg/books?id=FE...v=onepage&q=Cardano reversal tropical&f=false
Even without considering the Sun's motion, the simple fact that you do not make most astrological judgement based on whether it rained or it was 35°C or whether the month was hot in Egypt or cold in Rome should make anyone question this silly argument. (Even though that may be significant in itself, it is obvious that tropical astrologers completely ignore that.)
Thirdly, as you found out yourself many core significations of the signs are ''directly derived'' from the constellations. This is because the signs clearly originate after the imagery of the constellations, their names being an argument by themselves.
The other extra-zodiacal constellations, of which Ptolemy gives 36, are never reached by the planets so obviously they are not as important as the 12 zodiacal constellations. In my opinion, it is better to use those constellations as paranatellonta with the Ascendant and the 7 planets rather ecliptical projection -
https://www.astrologyweekly.com/forum/showpost.php?p=908585&postcount=2
They are to be examined in the same way as the signs.
Fourthly, as to daylight based techniques such as antiscia, it is notable that the early Hellenistic astrologers used antiscia based on sextiles and trines which are impossible in the tropical zodiac. As to the fact that some people on this forum believe that by using the sidereal zodiac makes you somehow live without understanding of the seasons (or without access to weather forecasting) furnishes no suitable or acceptable argument.
I am sure there is more to it. Even some tropical astrologers testify for precession-corrected transits and solar returns. In my opinion, all mention of planetary cycles and returns in Vettius Valens and elsewhere deserve only sidereal measurement since it is absurd to measure ''returns'' relative to the moving equinoxes (instead of a fixed zodiac). A sidenote to that topic is that a known tropical astrologer in the 16th century Francesco Giuntini (Junctinus) advocated a return to sidereal solar returns in 16th century.
I am trying to avoid bringing the zodiac problem on this board because it can digress all topics into the dark side, so if you have more questions, maybe you could consider the chill off-topic board -
https://www.astrologyweekly.com/forum/showthread.php?t=116254
This seems correct, I am just starting with astrology and trying to filter through the various sources. But you mention that you wanted to use it because it more closely follows the hellenistic traditions of the constellations, but then, what about the different lengths and additional constellations that aren't part of it?