In a recent thread we have discussed about the fact Ptolemy could use the method of ascensions or not, and links with Placidus method.

So I quickly re-did Ptolemy's last three examples of primary directions (Book III,11), when the significator does not fall on an angle.

I like very much Schmidt and Hand just I believe they are a little partial with Placido

The link is:

http://heavenastrolabe.net/ptolemy-and- ... irections/

margherita

It's been a while since I looked in those chapters but if I remember well, I believe that in the examples he gave he didn't do Sun or Moon to planet directions but only directions with angles. He only did in the theoretical explanation. So it still might be subject to interpretation what Ptolemy meant. Quite annoying, it's like someone giving an example of a difficult formula but only using examples which make it much more simple and in which one could skip part of the formula.

Apologies if my statement above is wrong, it's been a while ago and I might have misread Ptolemy.

Eddy wrote:It's been a while since I looked in those chapters but if I remember well, I believe that in the examples he gave he didn't do Sun or Moon to planet directions but only directions with angles. He only did in the theoretical explanation. So it still might be subject to interpretation what Ptolemy meant. Quite annoying, it's like someone giving an example of a difficult formula but only using examples which make it much more simple and in which one could skip part of the formula.

Apologies if my statement above is wrong, it's been a while ago and I might have misread Ptolemy.

Well, I did not quote Placido, I quoted Ptolemy.

In the first three examples, the significator, an example point at 0 Aries, is at the Ascendant, at MC, and at the Descendant.

In the rest of examples the significator is not in an angle. In fact Ptolemy writes:

Now let it be assumed that the beginning of Aries is not on any of the angles,

the examples in my article are these last ones, when the significator is removed from angles. I wanted just to show how easy it's the semiarc method and how Placido knew well Ptolemy.

margherita

margherita wrote:In the first three examples, the significator, an example point at 0 Aries, is at the Ascendant, at MC, and at the Descendant.

In the rest of examples the significator is not in an angle. In fact Ptolemy writes:

Now let it be assumed that the beginning of Aries is not on any of the angles,

the examples in my article are these last ones, when the significator is removed from angles. I wanted just to show how easy it's the semiarc method and how Placido knew well Ptolemy.

margherita

Thanks for the reply Margherita. Now I remember what my ambivalent feeling was with the examples of Ptolemy. Using 0?Aries namely always gives an easy calculation because the temporal hours of this point are the same as the equinoctal hours because 0? Aries is on the equator. So I think that Regiomontanus could also be considered as the system Ptolemy meant. But I too think that he meant semi-arc because they are one of the easiest to calculate by hand.

Eddy wrote:Thanks for the reply Margherita. Now I remember what my ambivalent feeling was with the examples of Ptolemy. Using 0?Aries namely always gives an easy calculation because the temporal hours of this point are the same as the equinoctal hours because 0? Aries is on the equator. So I think that Regiomontanus could also be considered as the system Ptolemy meant. But I too think that he meant semi-arc because they are one of the easiest to calculate by hand.

Actually, recalculating Ptolemy's example with the Regiomontanus method gives different results, as noted by Morin in Astrologia Gallica 22.1.9. Morin argues from the assumption that Ptolemy meant to direct according to the 'modus rationalis' of Regiomontanus, and criticizes him for his sloppy work. In reality, of course, Ptolemy had it right (and Placidus understood his method correctly); it was Morin's assumption that was wrong.

Martin Gansten wrote: Actually, recalculating Ptolemy's example with the Regiomontanus method gives different results, as noted by Morin in Astrologia Gallica 22.1.9. Morin argues from the assumption that Ptolemy meant to direct according to the 'modus rationalis' of Regiomontanus, and criticizes him for his sloppy work. In reality, of course, Ptolemy had it right (and Placidus understood his method correctly); it was Morin's assumption that was wrong.

Argoli too in his Tabulae Primi Mobilis says there are two different methods in directing, the one "Ptolemy teaches with little clarity" and the rational one, ie Regiomontanus one.

margherita