In this episode of the serial I’m going to consider medieval directions. Or to be more precise, I begin to consider medieval directions.
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There is a small update in the Tools. I’ve added a new tool. This new tool can find a point of the ecliptic from its right ascension, oblique ascension, and oblique descension.
I thank rabbi Avraham Ibn Ezra for the inspiration 
Checking his method of cusps calculations, I felt a necessity of this tool.
Though, it is a usual thing in old-fashioned calculations in various house systems, actually. Regiomontanus has the same searching for the ecliptical point from its oblique ascension.
I considered the Hellenistic method of primary directions in two previous posts Primary Directions: the story of calculations (vol.1 and vol.2). Most Hellenistic astrologers directed this way. But there is a very important exception. This exception is Ptolemy.
Ptolemy was an eminent scholar of his time, the level of his knowledges and abilities was much higher than the level of a common astrologer of that time. Ptolemaic method of directions is much more advanced with respect to mathematics and astronomy, than the Hellenistic method I considered before, but his method wasn’t spread among Hellenistic astrologers.
Let’s consider the Ptolemaic method of primary directions as it is described in Tetrabiblos III,10.
I examined the system of ascensions of the Zodiacal signs used by Hellenistic astrologers. You can find it in the previous post of this line. This time we consider Hellenistic method of primary directions. Let’s consider an example of calculation of primary directions from the text of Paulus Alexandrinus.
I wrote two posts on story of primary directions. It was couple years ago, and now these posts are buried deeply in the archives of Angelicus Merlin Group. Therefore I decided to repeat that stuff and perhaps to develop the subject.
First of all, because primary directions are based on daily rotation of celestial sphere, we must have a mathematical model of this rotation to calculate directions. The first model of this rotation was made in Babylon, but astrologers of Hellenistic period mostly call it “according to Egyptians”.
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