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OK. So I had to switch to Neo-Converse (directions against the diurnal rotation) to get the 59 value because traditionally the 71 arc is the same in both directions.
Image
Moving the MC backwards so that it meets the Sun in the west is not the same arc as moving the Sun forward to meet the MC because they are at different declinations (the MC of course has the entire range of declination except that the ecliptic would have a different declination at the MC during the course of the day). The traditional arc is always measured from east to west which would use the arc that the Sun would trace in the sky which would give a different proportion of the DSA than the MC arc going backwards.
Last edited by zoidsoft on Thu May 14, 2015 8:09 am, edited 2 times in total.
Curtis Manwaring
Zoidiasoft Technologies, LLC

19
This makes some sense to me but Zoller's instructions just state that you get the arc of direction by getting the difference between the Sun's RA and the MC's RA and that you subtract one from the other depending on what quadrant the Sun is in... Is it not this simple? Which is more correct, the later time or the earlier time?

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Lazarus wrote:This makes some sense to me but Zoller's instructions just state that you get the arc of direction by getting the difference between the Sun's RA and the MC's RA and that you subtract one from the other depending on what quadrant the Sun is in... Is it not this simple? Which is more correct, the later time or the earlier time?
That is correct. Zoller being the traditionalist would use the 71 value because NC (neoconverse) is a modern interpretation. There are actually 3 different formula's (in the proportional semi-arc method) that can be used depending upon what points are being used as significator and promissor. Computer software typically uses the long variation of measuring the proportions of one point in the sky (not on the asc or mc) to another because it can handle all situations (of planets not on the asc or mc which is frequently the case). It is shorter and quicker to do it your way by hand (right ascension), but that is the only case you can use the right ascensions in that way (to a point crossing the MC). You'd use the oblique ascension/descension if you're measuring the proportion of a point to the ascendant or descendant and finally there is the long formula that can apply to all situations (imagine a planet that happens to be exactly on the MC and one that happens to be on the ascendant for instance).
Curtis Manwaring
Zoidiasoft Technologies, LLC

21
Typically what happens is you will want to find the arc (proportion) of one planet (lets say in the 10th house not exactly on the MC) to another planet (lets say in the 11th). In this situation you cannot use subtraction of right ascensions. You have to ask yourself what constitutes a conjunction in the sky when two planets situated in this way will typically trace arcs either above or below the other. In one case lets say Jupiter in the 10th we trace an arc to Mars in the 11th. If Jupiter has a higher declination, it will usually pass above Mars, but which kind of vertical line do we draw for Mars? Again it will be different if you use the bodies with or without latitude. And then using the arc from Mars to Jupiter would again typically be different because it is likely they are not at the same declination.

The Regio (circle of position) method imagines a "horizon" being drawn for each planet and then uses the oblique ascension or descension calculation to get the differences between 2 points. It's an elegant solution mathematically, but it is not what Ptolemy describes in the semi-arc method.
Curtis Manwaring
Zoidiasoft Technologies, LLC

22
If you're trying to find out when fame will occur (usually what Sun conj MC means), you might want to check out zodiacal releasing from the lot of spirit (the lot of the Sun) because fame is usually a process, not a "hit" that comes and goes. For instance one does not usually become obscure after such an occurrence, but is instead remembered for their contribution. Before this though, one should understand Valens eminence method using the trigon lords in order to understand the stature of the nativity.

http://www.csus.edu/indiv/r/rileymt/Vet ... entire.pdf
Curtis Manwaring
Zoidiasoft Technologies, LLC

23
Wow the Valens sounds very interesting, I will read it when I can. I guess I just need to do some more work in order to understand exactly what is happening mathematically with these directions. The thing that worries me is that in the lesson on primary directions given by Zoller he only gives three methods of calculating these directions. They are I. Directing by Right Ascension II. Directing by Oblique Ascension III. Directions involving degrees not angular
Now I tried the last method to see if I could arrive at the 71 years arc but it did not yield this result and so I may try it again. However in Zoller's own natal chart which he uses as an example the MC is first directed to the Sun which is in the 11th and the method he uses is to get the difference between their RAs. He then directs the MC to Jupiter, which is in the 9th and uses the exact same type of calculation... hence my confusion about the matter...

I also really appreciate your interest in helping me out. Cannot thank you enough as this is very helpful because it is challenging me to really understand the math and astronomy.

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Lazarus wrote:really understand the math and astronomy.
Hi Lazarus,

I've only read the thread on the diagonal, but I'll post here links to two articles I wrote regarding the Primary Directions. It presents a very simple explanation (I hope) for the diurnal/nocturnal arcs, and a simple formula to calculate the Primary Directions using the proportional semi-arc method.

* On Diurnal and Nocturnal Arcs: http://blog.flatangle.com/2014/diurnal-nocturnal-arcs/
* Primary Directions, a simple approach: http://blog.flatangle.com/2014/primary- ... ns-simple/

The equation is correct, as I demonstrate in the second article, and I have implemented it in flatlib.

Hope it helps you cross check your calculations! :)


Jo?o Ventura

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Lazarus wrote:The thing that worries me is that in the lesson on primary directions given by Zoller he only gives three methods of calculating these directions. They are I. Directing by Right Ascension II. Directing by Oblique Ascension III. Directions involving degrees not angular.
Those are the 3 formulas that I told you about in regards to proportional semi-arc directions. You can only use the difference in right ascensions in the case where one of the points is directed to the MC. The 2nd is to be used when directing a point to the horizon and the 3rd is the longest formula for use in any situation.

All direction types are about defining what constitutes a direction. As Martin Gansten says, there can be no argument about when a planet crosses the horizon or meridian. However what constitutes a conjunction between points not on these planes is a matter of interpretation. Ptolemy said that when a planet sweeps the same proportional arc that another planet has in regards to it's proportion of distance between the asc and mc, then they are considered conjunct.

So what is done is to find where the significator is (lets say that it has 1/2 the arc between the ascendant and mc). If the diurnal semi-arc is 108 degrees, then 1/2 of that is 54 degrees. Then the arc of the other planet must be considered and if the promissor's arc would total 122 degrees between the asc and mc, then 1/2 of that arc is 61 degrees... The 1/2 technical term is called the PP (Proportional Point).

Now much determines what points to use, such as whether to use the bodies of the planets (with latitude) or their ecliptic projections, whether to do the same with aspects of these points (are they cast along the ecliptic? the equator? or symmetrical to the ecliptic (Bianchini)?) What constitutes a conjunction to these (proportions, theoretical horizons (regio and use of derived poles that one can cast a meridian or horizon line through)? All of these questions are answered differently depending upon the method being used (Polich Page, Under the Pole, Ptolemy, etc).

What is sought is called the AOD (Arc of Direction) and then a key is applied to this arc to convert it into time. Ptolemy is 1 degree = 1 year, Naibod mimics the solar motion, Placidus does similar but according to each particular day of motion (as a variable), etc...
Curtis Manwaring
Zoidiasoft Technologies, LLC

26
Joao Ventura those are helpful articles you've written. I'll probably have to reread them. One thing that would make them clearer is if you actually worked out the examples mathematically instead of just giving the formula.

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Curtis based on everything I still am not understanding how the longer arc for the Sun/MC is more correct from an ancient of ptolemic standpoint as it seems that all the sources I am reading point to getting the difference between RAMC and RAPlanet for the directional arc for planets above the horizon and the MC... perhaps I'm not clearly understanding this still