The Lot of Fortune
Apolgies for the rubbish in the previous post. I was having problems with my tablet's keyboard. LOL
Firstly, the Lot of Fortune is not of Arab origin (or for that matter Persian or Jewish). It dates back to the very beginning of Horoscopic Astrology and is of Hellenistic origin. The Greeks referred to it as a Kleros or in English, a Lot. Originally the word meant a plot of land that citizens were given (or allotted). We still use the word in that sense, such as allotments, or parking lots. It's astrological meaning derives from that process, it's what is allotted to you by the gates or the cosmos, or God.
The Latin translation of Pars, doesn't really have quite the same meaning and the use of the term, Arabic Part, is positively misleading. The system of Horoscopic Astrology was in part designed around the Lot of Fortune and the other Lots (Kleroi).
The system also included the interpretation of charts according to whether they were day or night chats. The previous chart you used was also a day chart (Sun above the horizion) One of the subtle differences is that the calculation of the Lot differed depending on whether it was a day or a night chart.
For a Day chart you start at the Sun and count the number of degrees to the Moon, you then project that distance from the Ascendant-(in the same direction as you counted (either clockwise of anti-clockwise).
For a Night chart you start with the Moon and count the number of degrees to the Sun. You then project that distance from the Ascendant, again in the same direction that you counted.
Mathematically the Lot of Fortune is calculated:
Day: Ascendant + Moon - Sun
Night: Ascendant + Sun - Moon
In both cases the Sect light (Sun by day, Moon by night) carry's the light to the out of sect light. It carries the light into the darkness, or if you like, it brings the light of the cosmos into the physical body - it invests the body with a soul. It is therefore principally concerned with the physical body and what befalls it, such as accident, disease, the beneficence of others, the malfeasance of others.
The only exception to this method of calculation was Ptolemy, who used the Day formula as his only formula. As Ptolemy survived into modern times, when many of the others were lost, or only survived through Arab intermediaries, meant that Ptolemy's calculation was viewed as the correct one, and the formulae that came via the Arab Astrologers was mistaken or even invented by them.
I always use the original formulas for day and for night calculations but you will find that many Horary Astrologers use Ptolemy's formula because Lilly believed that Ptolemy was the original version of Astrology and the Arabs were deviant.
Interpretation is mainly from the Lord of the Lot (planet that rules it). It's place in the chart is also relevant, especially if it's angular or aspects the Ascendant by whole sign.