Skyscript Astrology Forum

Now the sign of Aries as a whole, because it marks the equinox, is characterized by thunder or hail, but, taken part by part, through the variation in degree that is due to the special quality of the fixed stars, its leading portion is rainy and windy, its middle temperate, and the following part hot and pestilential. Its northern parts are hot and destructive, its southern frosty and chilly. - Robbins, F. E. (1940). Tetrabiblos (Vol. 435). Loeb Classical Library.
http://penelope.uchicago.edu/Thayer/E/R ... C*.html#11

If I understand this correctly, Ptolemy says that the whole weather of the sign is produced by the equinox, but that the ''decans'' or leading, middle and following parts are based on the fixed stars.

Does anyone know a source in the late Medieval or Renaissance period using those indications for meteorology? Did they apply precession - using the tropical zodiac for the whole part, but fixed stars for the decans and northern and southern parts (probably used with planets like the Moon, since the Sun never travels north and south of the ecliptic)?

Or did they assume tropical zodiac for both, ignoring the mention of fixed stars in the chapter? Also if it is true that those qualities are based on fixed stars, does it tell us something about the relationship of the tropical and sidereal zodiac at the time of Ptolemy? For example, why would earthquakes, droughts and destruction be caused by cloudy fixed star clusters rather than specific degrees of the zodiac.

I checked a couple of medieval and early modern sources, but probably not the right ones to find anything about Ptolemy's meteorological astrology. Then I turned to the commentaries, and it seems that at least Ibn Ri???w??n and Cardano take the remark about the equinox as Ptolemy is referring to the tropical sign (which is subjected to precession), but the three thirds and the northern and southern parts are considered to be understood as the parts of the stellar configuration.

In any case, Ptolemy is adapting older material whose traces are found in Valens and Hephaestio. Incidentally, the corresponding passage from Valens has been discussed here:

http://skyscript.co.uk/forums/viewtopic ... highlight=

Levente Laszlo wrote:I checked a couple of medieval and early modern sources, but probably not the right ones to find anything about Ptolemy's meteorological astrology. Then I turned to the commentaries, and it seems that at least Ibn Ri???w??n and Cardano take the remark about the equinox as Ptolemy is referring to the tropical sign (which is subjected to precession), but the three thirds and the northern and southern parts are considered to be understood as the parts of the stellar configuration.

In any case, Ptolemy is adapting older material whose traces are found in Valens and Hephaestio. Incidentally, the corresponding passage from Valens has been discussed here:

http://skyscript.co.uk/forums/viewtopic ... highlight=

Interesting, despite the difference of 8 degrees between the tropics, the considerations are similar, which probably confirms that they were based on stellar considerations.

I still have trouble understanding how would one go about moving each third around the tropical zodiac - does he adopt a separate frame of reference that is sidereal from the second century, or simply move the considerations every 720 years. Of course, that is said if exactitude was meant, rather than general observation of the part. Ptolemy is somewhat ambiguous in this part.

It is interesting you connect the source to Nechepso and Petosiris. Perhaps the assignment to decans is not coincidental. Decans were also based on stellar considerations.

Ptolemy might have thought of the tropical frame when talking about the sign in its entirety, and the constellational when describing its parts. At least this is how the commentators seem to interpret him.

But if you ask me, I say, while he was rationalizing and tropicalizing astrology, he left behind quite a few loose ends (constellational considerations, topical places, coerced numerical values like the "ages of men", undefined or idiosyncratically used concepts like testimony, overcoming, spear-bearing, etc.; just to mention some).