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margherita wrote:
jventura wrote: As i said, my "hand" calculations don't match pyMorinus anymore,
Gimme an example, a chart with data, Ascendant and Moon and a direction you want to check.

margherita
I've been testing it with my own data.. I'll check with other data, to see if the calculations match, and if not, I'll post them here.

Thanks,
Jo?o Ventura

Edit: BTW Margherita, what did you mean in your previous post: Morinus can deal very well with semi-arc directions (latitude 0), more specificaly, the latitude 0?

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jventura wrote:
Edit: BTW Margherita, what did you mean in your previous post: Morinus can deal very well with semi-arc directions (latitude 0), more specificaly, the latitude 0?

semiarc directions could be calculated with planetary latitude. But Ptolemy method is with no latitude.

Obviously I have not checked everything but just what useful (and traditional). So I'm sure that semiarc without latitude are perfectly right in Morinus, but I have not checked all the latitude options, because I did not care.

margherita
Traditional astrology at
http://heavenastrolabe.wordpress.com

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margherita wrote: semiarc directions could be calculated with planetary latitude. But Ptolemy method is with no latitude.
Oh, you meant ecliptical latitude! For a moment I thought you were talking about equatorial latitude.. :)

Thanks,
Jo?o Ventura

36
Hi everyone,

I've finished writing a new blog post about a simpler and generic formula for the calculation of Primary Directions using the proportional semi-arc method.

You can find the post here: http://skyplux.wordpress.com/2013/05/19/primary-directions-a-generic-approach/

People who have been doing hand calculations of Primary Directions know that there are three different classes of formulas to calculate PD's, namely directions to a meridian (easy one), to the horizon (quite boring, because of the oblique ascensions), and to a planet or point.

In section 4 of the post, I show one simple formula which is generic enough to solve the three mentioned problems in the same way. I demonstrate mathematically that the formula is adequate to solve each of the single "problems". The formula is just another way of expressing the semi-arc method, but it seems simpler to me..

[for software developers]
For software developers this means that instead of three different functions, you only have one, which is simpler. To people who like to calculate PDs by hand, it means less formulas (and no Oblique Ascensions!).
I've implemented this method in skyPlux and reduced my Primary Directions calculations from 800 lines to about 25 lines of code, including one function to compute the diurnal/nocturnal arcs of a planet and another to find if a planet is above/bellow the horizon.
[/for software developers]

I've compared my results to http://www.astrotexte.ch/sources/primaries.jsp by Dr. R?diger Plantiko, a resource identified as reliable by Martin Gansten in his book, and the results match with an error less than 1".

Later, I will compare them to pyMorinus, as promised, and if I find any errors, I should post them here so Margherita can check them, since I believe Margherita has been helping the programmer of pyMorinus on the PDs module..

Finally, I believe the formulas are correct, but if anyone detects any error, please let me know!


Thanks,
Jo?o Ventura

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jventura wrote: In section 4 of the post, I show one simple formula which is generic enough to solve the three mentioned problems in the same way. I demonstrate mathematically that the formula is adequate to solve each of the single "problems". The formula is just another way of expressing the semi-arc method, but it seems simpler to me...
In the proportional semi-arc method, the only formula needed is the one for mixed ascensions. Directions to the Ascendant (oblique formula) and the MC (simple subtraction) are simplified special cases where the formula can be reduced from the method of mixed ascensions.
Curtis Manwaring
Zoidiasoft Technologies, LLC

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zoidsoft wrote:
jventura wrote: In section 4 of the post, I show one simple formula which is generic enough to solve the three mentioned problems in the same way. I demonstrate mathematically that the formula is adequate to solve each of the single "problems". The formula is just another way of expressing the semi-arc method, but it seems simpler to me...
In the proportional semi-arc method, the only formula needed is the one for mixed ascensions. Directions to the Ascendant (oblique formula) and the MC (simple subtraction) are simplified special cases where the formula can be reduced from the method of mixed ascensions.
Hi Curtis,

yes, that's it! That is what I tried to demonstrate in that "section 4" of the post..
Probably it was already mentioned in Gansten's course! I didn't took the course, neither searched for other sources.. But this is way simpler for me now, so the posts (and the general idea) will stay available, may anyone need that info in the future.. :)


Jo?o Ventura