I am still in the beginning exploratory stage of astrology, therefore if I state how to use divisional charts I may have to recant things later on, but I will state some ideas I have read on various uses of the divisional charts.
Some people interpret certain divisional charts the same way as the D-1 root chart, e.g. the D-9 and/or the karakamsha lagna: D-1 AK placement in the D-9 as the 1st house.
There has been much talk about analyzing the D-9 charts for synastry in marriage, but those who did this also compared many other things, besides just the D-9 charts, and so this has given some the wrong impression that the D-9 is related to marriage, which I do not believe. I think the only reason the D-9 was used in synastry analysis was because the D-9 is perhaps the most powerful divisional chart as far as planetary strength and showing the nature of a thing or person ? in regards to analyzing it as a stand-alone chart or even comparing it with another person's D-1.
Some people interpret certain divisional charts by analyzing certain dasha sequences using the D-1 root and that particular divisional chart, e.g. the D-1 planets with the D-60 planets in conjunction with the moola dasha.
Some people interpret divisional charts by interpreting and understanding the names of the deities which rule various divisions, e.g. the D-27 and D-60.
Some people used the divisional charts as a measurement of planetary strength in a similar manner as in if we see, e.g., the Moon in Scorpio in the D-1, we would consider this to be a debilitated Moon, and so if the Moon is in Scorpio in many divisional charts used for this purpose, then we would consider the Moon to be afflicted, even if the D-1 Moon is exalted.
Here are two examples of using the divisional charts as a measurement of planetary strength:
Dvadashavargiya Bala (12-fold strength)
1) D-1 sign placement of each planet (e.g. exalted, friendly with ruler of that sign, etc.)
2) D-2 sign placement
3) D-3 placement
4) D-4
5) D-5
6) D-6
7) D-7
D-8
9) D-9
10) D-10
11) D-11
12) D-12
A table is drawn listing each planet from Sun to Saturn (not nodes) in a column, then the top row lists each of these divisional charts according to the standard of whether that planet is Friendly, Neutral, Inimical, or Ruler of that Sign placement or the ruler of that Sign in relationship to the planet in that sign in each D-1 through D-12 placement. Then the results are tallied up in another table with the planets given a category of auspicious, neutral, or adverse placements, and one can then see if that planet is placed in favourable signs for itself, or adverse signs, or neutral signs, overall. This enables a more comprehensive look at how the planet will act for that natal chart.
The second example of using divisional charts for measuring planet strength is called the Panchavargiya Bala or 5-fold strength. This is based on 5 factors: Ksetra Bala, Ucca Bala, Hadda, Drekkan, and Navamamsa.
Ksetra Bala this is based on a tally of points given for each planet in sign placements in the D-1 based on whether it owns the sign it is in, or it is friends with the ruler of the sign it is in, or if it is neutral to the ruler of its sign placement, or if it is an enemy of the ruler of the sign it is in.
Uccabala: This is a measurement of how near or far a planet is to its exaltation and debiliatation points.
Hadda or ?limit? is the Egyptian Bounds/Terms placements in the D-1.
Drekkan is the planet placement in the signs of the D-3.
Navamamsa is the planet placement in the signs of the D-9.
Both the 12-fold strength and 5-fold strength can be, and are, used to analyze the solar return chart. However, these divisional charts are different from the Addey system.
Which brings me back to the mention of the D-9 and H-9 being the ?same,? in fact, the D-9 and H-9 are not the same, in spite of the fact that the end result looks the same - this is a
coincidence. Let us look at the principle of calculation of the D-9:
D-9 ?
The Nav?m?a calculation are for a Movable R??i from there itself, for a Fixed R??i from the 9th thereof and for a Dual R??i from the 5th thereof.?
I believe the calculation rules of each divisional chart give clues as to what that divisional chart is based upon, and therefore how it may be of interpretive use. Notice that, contrary to the Addey system and parivritti charts, the divisional charts have a certain basis for each type of sign and sometimes the calculations are reversed in alternating signs and such. Notice that the focus of the D-9 calculation is on Cardinal signs starting with the same Cardinal sign; Fixed signs start with the 9th sign from themselves; and Mutable signs start with the 5th sign from themselves.
This tells me there is something important for Cardinal Signs in relation to themselves; something important in regards to Fixed signs and the 9th house; something important in regards to Mutable signs and 5th houses. It also tells me the D-9 has some relation to the trikona houses, or triplicities, or both. I believe these calculation rules are important for understanding the nature of each unique divisional chart. The reason I say this is because the Addey system divides up signs into numbers and repeats from the start of the zodiac to the end, in a cyclical pattern, thus deserving of, e.g. the title: H-5 and not D-5.
This is how the Addey system is different, because the Addey system only used one principle for everything, and the divisional charts use many different principles, depending on which divisional chart it is.