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Martin Gansten wrote:
Michael Sternbach wrote:Hope you can find a moment for checking out the references you have in mind soon. We do need to know! :lol:
I'm sure others have those works on their shelves, too, but I'll try.
Who are those early modern authors you mentioned? I encountered two different methods of determining moiety, however, their results are the same.
Yes, you are right: a moiety or 'average of their respective orbs' would necessarily be the same as assigning 7°30′ to either side for the Sun, etc. (I was thinking of authors like Lilly, e.g., CA p. 107.) The question of half-orbs becomes more pointed when discussing things like a planet being conjunct a cusp or some other point that doesn't have an orb of its own.
The latter view being particularly useful when it comes to aspects with astrological elements that supposedly have no "radial field" of their own (ASC, MC, Arabic parts, Lunar nodes etc.) -- yes, that makes sense.
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Martin Gansten wrote:The chapter that I quoted before from Abū Maʿshar (Great Introduction VII 5, 9th century CE) actually has a very full discussion of application and separation both by conjunction and aspect, running over several pages and including the concept of moieties as one consideration among others. I'll just quote part of the section on conjunctions here (transl. Burnett):
If one planet conjoins a number of planets in different degrees and is lighter than them, it applies to the nearest planet and the nearest planet ⟨is applied⟩ to it. When the light planet passes the slow one by one minute or less, it separates from it. When a planet separates from another in conjunction and it does not apply to a⟨nother⟩ planet, one of them is in the other’s nature as long as they are in the sign in which they conjoined. The most powerful mixing of their natures is when they are in the same term and they are not separated by more than the quantity of half the body of ⟨the planet⟩ of fewer degrees. When one of them leaves the term in which they conjoined, their mixing becomes weaker. In addition to this, when their separation is more than the quantity of half their bodies, the mixing of their natures is weaker. If another planet meets it at its separation from it before it leaves the term in which they have conjoined or before it separates from the first planet by the quantity of half the body of ⟨the planet⟩ of fewer degrees, the light planet is in the nature of the two planets, i.e. the one separating from and the one applying to it. When it separates from the second planet bodily, its condition with it is like its condition with the first planet from which it had separated. If a number of planets conjoin and they are in the same degree and minute or they are near in degrees, then they share each other’s natures, and each of them remains in the power of the other’s nature until it separates from it by the quantity of half its body. If their conjunction is at the end of the sign, the power of half their bodies is in the sign which follows them. When the lighter of the planets moves to the second sign, it remains in the nature of the other until it is distant from it by the quantity of half its body, but this kind of mixing of their natures is weak.
Edit: the word 'body' as used here is what we today would call 'orb'.
That's an awesome find, Martin! Much appreciated. :)

Now we can date the idea of moiety orbs at least to the 9th century AD.
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Martin Gansten wrote: Edit: the word 'body' as used here is what we today would call 'orb'.
But here we must not forget that, what we call orb, is only the length of a planet's ray.

Saturn's orb is 9 degrees, i.e. his Influence is 9 degrees before and 9 degrees after him.

Thus the whole body of Saturn is 18 degrees, and his 'half body' of the quotation above is the same as his orb of 9 degrees.

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You're absolutely right, Johannes! I was in a bit of a hurry when chasing up that reference yesterday, but looking at it more closely now, I see that Abū Maʿshar talks of 'half the body of the planet of fewer degrees'. So if the conjunction is between Saturn and the Moon, then it would be weaker after the Moon has separated from Saturn by 9°. So this is not the 'average' mentioned by al-Bīrūnī, if indeed 'average' is correctly translated in the first place (Arabic is not one of my languages, unfortunately).
https://astrology.martingansten.com/

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The divergent use of "half orbs" with different authors can indeed be confusing. I must confess that I was in a bit of a hurry myself and intended to dedicate myself to the entirety of Abū Maʿshar's text on application and separation later.

Thank you for the clarification, Johannes.

Of course, that leaves us with the question if any of the other sources mentioned by Martin might be relevant in this regard or if we have to content ourselves with al-Bīrūnī's respective remark as the earliest tangible reference to moiety orbs.
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