My understanding of the divisional charts comes from Birhat Parashara Hora Sastra (BPHS) - it is an account of all slokas written on Vedic astrology by Sage Parashara, who many consider as the founder of Vedic astrology :) You can find an online version of BPHS at this link. So, there are 16 divisional charts and each one of them has a specific purpose. Please have a look at this table.

Divisional Chart	Vedic Name	Main purpose	Shad Varga	Saptha Varga	Dasa Varga	Shodasa Varga
D-1	Rasi chart	Physical appearance, and Life's direction	6	5	3	3.5
D-2	Hora	Wealth	2	2	1.5	1
D-3	Decanate	Happiness through co-borns	4	3	1.5	1
D-4	Chaturthamsa	Good luck, Childhood, and Home/Property	-	-	-	.5
D-7	Sapthamsa	Children, and Grandchildren	-	1	1.5	.5
D-9	Navamsa	Spouse, and Married life	5	2.5	1.5	3
D-10	Dasamsa	Career, Power, and Authority	-	-	1.5	.5
D-12	Dvadasama	Parents	2	4.5	1.5	.5
D-16	Shodasamsa	Vehicles, Conveyance, and Happiness	-	-	1.5	2
D-20	Vimsamsa	Spiritual and Religious beliefs	-	-	-	.5
D-24	Chaturvimsamsha	Higher education, Intellect, and Academic achievements	-	-	-	.5
D-27	Bhamsha	Strengths & Weaknesses (Physical & Mental)	-	-	-	.5
D-30	Trimsamsa	Misfortune	1	2	1.5	1
D-40	Khavedamsha	Luck from mother's side of the family	-	-	-	.5
D-45	Akshvedamsha	Luck from father's side of the family	-	-	-	.5
D-60	Shashtiamsha	All general indications. Some say it represents effects of past-life karmas.	-	-	5	4

There are 4 methods (Shad Varga, Sapta Varga, Dasa Varga, and Shodas Varga) that assign weights on a 20 points scale to divisional charts. Based on the average of the points assigned to these charts the D-1, and the D-9 are important divisional charts. I'll add the D-10 chart to the list as it is used to analyze the career direction. So my recommendation for you would be to do a detailed analysis of the D-1 chart (the main birth chart) and read the D-9, and the D-10 chart alongside it. So, let's discuss these D-charts:

D9-chart

If you'd prefer watching a video on this topic, then please click here. If you prefer reading, then here we go. The D-9 chart is an extension of the 9th house, which is the house of luck and good fortune. But why is it analyzed to determine the characteristics of the spouse and the quality of the married life? Perhaps BPHS is alluding to the fact that finding a good life partner is a matter of good fortune. Hope you agree. Before we learn how to use the D-9 chart, I am sharing the slokas on Navamsa as stated in BPHS & Saravali. I've tried to explain them and I've broken them down in different categories. So, let's begin:

Theme - Physical appearance
"This sloka from Saravali states that if a malefic or a benefic if be in own Rasi or Navamsa, the effects will be right from birth, In other cases, it will be in the course of one's life that these effects will come to pass”
This dispels the common notion that the D-9 chart is only relevant when you are married. The D-9 chart is relevant right from birth e.g. if someone has Mercury in the Navamsa of Virgo then that person will show signs of intelligence from childhood.

"This sloka from Saravali states that the native will be influenced in appearance, disposition etc. by the strongest planet or the ascendant lord or the Navamsa ascendant lord.”
So, your appearance and physical well-being could be determined by the Navamsa Ascendant lord.

"This sloka from BPHS states if there be a birth in one of Aries, Taurus and Leo ascendants containing either Saturn or Mars, the birth of the child is with a coil around a limb. The corresponding limb will be in accordance with the Rasi or Navamsa rising."
This sloka confirms the importance of the D-9 chart right from birth.

Theme - Comparing the D-1 chart to the D-9 chart
The following slokas compare the main birth chart (D-1 chart) to the D-9 chart. So, these slokas study the placement of the house lords of the D-1 chart in the D-9 chart. Have a look at this sloka.

“Should the 5th lord be in his own house, or in own Navamsa or in exaltation, the native will be endowed with comforts related to lands, conveyances, houses etc. and musical instruments”
So, if the lord of a house of the D-1 chart is exalted, or is in own sign in the D-9 chart then that house would become strong. E.g. if you are a Pisces ascendant then your 5th house lord is Moon, and if Moon is in the sign of Taurus (exalted) or is in Cancer (own sign) in the D-9 chart then condition of the 5th house (material comfort) becomes very strong. Hope this is clear.

“If the lords of the 5th, 8th and ascendant are in own Navamsa, own Rasi, or in a friendly sign, the native will enjoy a long span of life”
If the lords of the 1st, 5th, and the 8th house of the main birth chart are in a strong position in the D-9 chart then it is an indication of good physical well-being.

“Should the 9th lord be in deep exaltation while Venus is in angle from the ascendant and Jupiter is in the 9th from Navamsa Ascendant, the father of the native will enjoy a long-span of life.”
If the 9th house lord is in a strong position in the D-9 chart then the father would enjoy good health.

“One will own beautiful houses and beds and be endowed with superior scented articles and pleasures if the Moon happens to be the l2th lord and be exalted or be in own sign/Navamsa or be in the llth/9th/Sth in Rasi/Navamsa”
A strong position of the 12th house lord in the D-9 chart is an indication of you enjoying the pleasures of the world. Especially if the lord of the 12th house is Moon.

Theme - Houses in the D-9 chart
“One will have two wives if the 7th lord is in fall, or in a malefic sign along with a malefic while the 7th house, or the 7th house in the Navamsa belongs to a eunuch planet”
The condition of the 7th house in the D-9 chart determines the possibility of multiple marriages.

“If Saturn is in the 10th along with a debilitated planet while the lOth from Navamsa ascendant is occupied by a malefic, the native will be bereft of (virtuous) acts.”
The condition of the 10th house in the D-9 chart has an influence on your career. So, houses in the D-9 chart mean the same as they do in the D-1 chart.

Miscellaneous
"This sloka from BPHS states that if the Sun and the Moon join in one bhava (house) and fall in one Navamsa, the native will be nurtured by 3 different mothers or 2 fathers”
So the placement of Sun & Moon in the D-9 chart could be used to determine the relationship with parents.

“Atma Karaka in benefic's Rasi or Navamsa will make one wealthy”
If the planet holding the highest degree (Atmakarak) in your birth chart is in a strong position in the D-9 chart then you would be wealthy.

“Should the ascendant lord and the 5th lord exchange their signs or if Atma karaka and Putra Karaka are in the ascendant, or in the 5th, or in exaltation sign, or in own sign, or own Navamsa, or in aspect to a benefic, Maha Raja yoga is produced”
So, we are looking at the placement of the 1st house lord and the 5th house lord to determine if we are going to attract wealth. We are doing the same for the Atmakarak (planet holding the highest degree) and the Putra Karak (planet holding the 5th highest degree). We are analyzing the placements of these planets in the D-9 chart to determine a Raj Yoga.

What did we learn from these slokas? We need to analyze the placement of planets in the D-9 chart. The houses in the D-9 chart mean the same as they do in the main birth chart. We need to compare the main birth chart to the D-9 chart i.e. we need to analyze the placement of the house lords of the D-1 chart in the D-9 chart. And then we look at the Atmakarak, Putrakarak, and Darakarak to find more clues. From a marriage perspective, here's how to use the D-9 chart.

Let's now discuss how to analyze the D-9 chart
You need to study the placement of the following 5 planets in the D-9 chart, they are:
1. Lord of the 7th house in the main birth chart

So, first determine which planet is the lord of the 7th house in the main chart and then examine where is it placed in the D-9 chart. This will give you an indication about your spouse.

2. Venus - Natural signifactor of marriage

Venus is the natural signifactor of marriage and it also represents a wife in Man's chart. So Venus' placement in the D-9 chart would give you more clues about the spouse and the quality of your married life.

3. Jupiter - only for women

Jupiter represents a husband in a woman's birth chart and so its placement in the D-9 chart would give you clues about your husband.

4. Darakarak (DK) - the planet that is holding the lowest degree in the main birth chart

The Darakarak is the inconstant signifactor of the spouse. The placement of the DK in the D-9 chart would further narrow down the characteristics of the spouse. The Darakarak is taken from Jaimini astrology. Just like Sage Parashara, Sage Jaimini has written extensively on Vedic astrology. Another interesting thing is that Sage Jaimini was taught astrology by Sage Veda Vyas, who was the son of Sage Parashara.

5. Lastly, the planets (if any) sitting in the 7th house in the D9 chart

This would give you an indication of the quality of your married life and indications of delay in marriage, if any.

In addition to this, you could also read the D-9 chart in isolation just like how you would read the main birth chart (D-1 Chart). But keep in mind that the objective should be to find common patterns between the main birth chart & the D-9 chart. Lastly, the divisional charts (D-2 to D-60) are derived from the main birth chart, the planets in the divisional charts are not physically changing their sign placement. For this reason, please do not use planetary aspects in the D-9 chart or in any other divisional chart. Aspects are only to be used in the main birth chart (D-1 Chart). Hope this makes sense.

D10-chart

It is mentioned in BPHS that the D-10 chart should be analyzed to determine one's career (livelihood) and to determine how much power & authority one would exercise in their life. To do this, you need to analyze the placement of the following 7 planets in the D-10 chart, they are:

1. Lord of the 10th house in the main birth chart

So, first determine which planet is the lord of the 10th house in the main chart and then examine where is it placed in the D-10 chart. This would give you an indication of your career direction.

2. Lord of the 6th house in the main birth chart

This would give you an indication of the nature of your work and your day-day work responsibilities.

3. Sun - Natural signifactor of career

Sun's placement in the D-10 chart would us an indication of how much power & authority you would exercise in your life.

4. Mercury - Natural signifactor of business

If Mercury is in a strong position in the D-10 chart then success in business becomes a possibility.

5. Saturn - Natural signifactor of service

If Saturn is sitting in a strong position in the D-10 chart or it is sitting in the 10th house or in the 6th house in the D-10 chart then you would be devoted to serving people - in the modern context, it is working in a routine based job in a services industry.

6. Atmakarak & Amatyakarak - the planet holding the highest & the second highest degree

Again, the concept of Atmakarak & Amatyakarak are taken from Jaimini astrology. The placement of the Atmakarak in the D-10 chart would give you an indication of your career direction. And the placement of the Amatyakarak in the D-10 chart would give you an indication of you are going to achieve your career goals.

7. Lastly, the planets (if any) sitting in the 10th house in the D-10 chart

This would give you an indication of your attitude towards, how much authority you would exercise in life, and in which sector/industry would you be working in.

D2-chart

The D-2 chart is an extentsion of the 2nd house and so wealth is to be seen from this D-chart. This is a unique D-chart because the ascendant and the planets are all going to occupy either the sign of Leo or Cancer. If the ascendant of the D-2 chart is Leo, then the planets would either be in the 1st house or in the 12th house in the sign of Cancer. And if the ascendant of the D-2 chart is Cancer then all the planets would either be in the 1st house or in the 2nd house in the sign Leo. Please take some time to absorb this information.

Let's now discuss how to analyze the D-2 chart

You need to study the placement of the following 3 planets in the D-2 chart, they are:

1. The Lord of the 2nd house in the main birth chart

So, if the lord of the 2nd house of the main birth chart is in the 2nd house in the D-2 chart then wealth would be accumulated with the help of the family. If it is placed in the 12th house in the D-2 chart then money would be made in a foreign land, and lastly, if it is placed in the 1st house in the D-2 chart then you are going to be a self-made human being.

2. Jupiter - the natural significator of the 2nd house (house of wealth)

You need to do the same analysis for Jupiter as you've done for the lord of the 2nd house.

3. Amatyakarak - Planet holding the second highest degree

In the context of money, Amatyakarak represents how you are going to make money. And so you need to do the same analysis as you've done for the lord of the 2nd house.

Let's now study the relationship between the placement of these planets in the D-2 chart. E.g. if the Lord of the 2nd house, Jupiter, and the Amatyakarak are all in the 1st house in the D-2 chart then there is a very high possibility of you making money all by yourself. Similarly, if they are placed in the 2th house then money would be made through your family, and lastly, if there are all in the 12th house then the possibility of making money in a foreign land is pretty high.
Now, let's see what happens when they are placed in different houses. Let's say the lord of the 2nd house is in the first house in the sign of Leo in the D-2 chart and Jupiter is in the 12th house in the sign of Cancer. In such cases, the planetary time periods (dashas) become very important. So, yes you are going to be a self-made human being but also during the dasha of Jupiter you would run into an opportunity to earn money in a place far away from your place of birth. Hope this is clear.

Let's see how is the D-2 chart calculated

Lord/Diety	Hora	Odd signs (1,3,5,7,9,11)	Evens signs (2,4,6,8,10,12)
Gods	0 - 15 degrees	Leo (Ruled by Sun)	Cancer (Ruled by Moon)
Ancestors	15 - 30 degrees	Cancer (Ruled by Moon)	Leo (Ruled by Sun)

First, a bit of mythology, if the longitude (degrees) of the planet in your main birth chart is between 0-15 degrees then that planet is ruled by the Gods else it is ruled by the Ancestors. BPHS states that Jupiter, Sun, and Mars (Males planets) do really well in the sign of Leo in the D-2 chart. Moon, Venus, and Saturn (Female planets) do really well in sign of Cancer and Mercury does well in both signs. Also, the planets would be most powerful in the first 1/3rd of the Hora, medium in the 2/3rd, and least powerful at the end of Hora. Let me explain this with an example, let's say you have Moon in the sign of Aries at 16 degrees. So the Hora of Moon would be Cancer (see table above) and would be very powerful because 16 degrees is right at the beginning of the Hora range 15 - 30 degrees. Hope this was clear.

D3-chart

In the D-3 chart, each zodiac sign is divided to 3 parts of 10 degrees each. And so we have 12 x 3 = 36 divisions, which are called Decanates. Brihat Jatak (another classic on Vedic astrology) has written extensively on this topic. The first basic exercise you can do now is to identify decanates of the planets, and the ascendant in the main birth chart (D-1 chart). E.g. if your Sun is in Libra 23 degrees then it is in the 3rd decanate. So, let's see what do the 3 decantes mean:

1st Decanate (0-10) degrees

If your ascendant is in the 1st Decanate then you'll work for the benefit of others, you would be a believer of justice, you would be intelligent, noble, would show people the right path, and give them the courage to fight. You would also be fond of travel & music. Also, if most of the planets are falling in the 1st decanate then you would show similar characteristics. Of course! the basic characteristic of the planet/ascedant lord has to be taken into account.

2nd Decanate (10-20) degrees

If your ascendant is in the 2nd Decanate then you would lead a disciplined life, would be hardworking, would be determined, and would achieve your goals for sure, even if it takes a long time. You would be powerful and would help others. Again, if most of the planets are falling in this decanate then you would show similar characteristics.

3rd Decanate (20-30) degrees

If your ascendant is in the 3rd Decanate then you would be detached from the wordly desires, would be frugal, spiritual, eternal wanderer, and would be a believer of age-old traditions and customs. You would also be a bit impulsive, aggressive, and ruthless. You would show such characteristics especially when you are going the time period of the planets/ascendant lord falling in this decanate.

Now, let's go a bit deeper, identify the decanate and the zodiac sign of the ascedant and that of the planets and see in which category are they falling into.

Category	Description	Decanates
Serpent	Danger from poisonous animals, betrayal, being apprehended, and legal issues could arise during the phase of the planet falling in serpent. If Moon is in serpent then would be quite short-tempered, impulsive, and aggressive during its phase. So basically, the phase of such planets is a phase to be very watchful.	Cancer(2,3) Scorpio(1) Pisces(3)
Kroor (Wicked)	If malefics are in Ayudha then during their time period defeat in battle, litigation, a physical injury, failure in initiatives, and unproductive travel could be the outcome. If the Moon is sitting in Ayudha then you could become quite aggressive, cruel, and a bit violent too. However if benefics are in Ayudha then the table is turned and victory is assured during its time period.	Aries(1) Cancer(2) Leo(1,3) Scorpio(1,2,3) Aquarius(1) Pisces(3)
Ayudha (Weapon)	If malefics are in Ayudha then during their time period defeat in battle such as sports, or litigation, a physical injury, failure in intiatives, and unproductive travel could be the outcome. If the Moon is sitting in Ayudha then you could become quite aggressive, cruel, and a bit violent too. However if Benefics are in Ayudha then the table is turned and victory is assured during their time period.	Aries(1,3) Gemini(2,3) Leo(3) Virgo(2) Libra(3) Sagittarius(1,3)
Pakshi (Bird)	If you have your ascendant as Pakshi then you could be an eternal wanderer, or would constantly travel for work. If Moon is in Pakshi then you would be quite fickle minded.	Leo(1) Libra(1,2) Aquarius(1)
Quadruped	If Malefics are in Quadruped then chances of injury through a vehicle or four-legged animals could be high.	Aries(2) Taurus(2,3) Cancer(1) Leo(1) Scorpio(3)
Pasa (Noose)	A phase of the planet in Pasa, if any, could lead to a desire of letting go of life.	Scorpio(2)
Nigada (Fetters)	A phase of the planet in Nigada, if any, could lead to apprehension during its time period.	Capricorn(1)

*1 = 1st Decanate (0-10 degrees), 2 = 2nd Decanate (10-20 degrees), and 3 = 3rd Decanate(20-30 degrees)

Now, let's discuss the application of Decanates in medical astrology. The overall association of houses with body parts is shown in the table below. But the decanate of the ascendant would narrow down the body parts associated with the houses. Please check this table now.

House No.	Overall	Ascendant Decanate 1	Ascendant Decanate 2	Ascendant Decanate 3
1st	Head, brain, hair, appearance, and skin	Head	Neck	Pelvis
2nd	Face, eyes (right eye), teeth, tongue, mouth, oral cavity, nose, and speech	Right eye	Right shoulder	Penis
3rd	Ears, throat, neck, shoulders, upper limbs, windpipe, food pipe, collar bones, part of the hand between thumb & index finger, mental stability, and physical growth.	Right eye	Right shoulder	Penis
4th	Chest, breast, lungs, heart, blood vessels of the thorax, and diaphragm	Right nostril	Right side of the body	Right thigh
5th	Upper abdomen, heart, stomach, liver, gall bladder, spleen, pancreas, and pregnancy.	Right cheek	Right side of the heart	Right knee
6th	Small intestine, kidney, mesentery, upper ureter, wounds, injury, common diseases, phlegmatic illness, tuberculosis, and eye problems	Right jaw	Right lung/breast	Right calf
7th	Large intestine, lower urinary tract, uterus, ovaries and testes, prostate gland, groins, anal canal, semen, and sexual union.	Mouth	Navel	Legs & Feet
8th	External genitalia, anal orifice, loss of a limb, affliction to face, chronic diseases, and longevity	Left jaw	Left lung/breast	Left calf
9th	Hips, thighs, and femoral arteries	Left cheek	Left side of the heart	Left knee
10th	Knee joints, and knee cap	Left nostril	Left side of the body	Left thigh
11th	Legs, and left ear	Left ear	Left arm	Left testicle
12th	Feet, left eye, disturbed sleep, mental imbalance, hospitalization, and crippled limbs.	Left eye	Left shoulder	Anus

As shown above, if your ascendant is in the 1st Decanate then the body parts associated with the houses would be from head to neck, if it is in the 2nd Decanate then the body associated would be from neck to pelvis, and if it is in the 3rd Decanate then the body parts associated would be from pelvis to feet. The overall body parts associated with the houses should always be taken into consideration to identify a health issue. Let's see how to do that, check in which house(s) are malefics (Mars, Rahu, Ketu, Sun and Saturn) placed in the main birth chart and the D-3 chart. Now check, which body parts are associated with those houses, and finally check if you are going through a time period of a malefic planet, if yes then a health issue related to the concerned house & planet would arise.

The 22nd decanate from the ascendant in the main birth chart is of special interest in medical astrology. Let's see how to calculate the 22nd decanate, if your ascdenant is 23 degrees Libra then this becomes the 1st Decenate and so 22nd would be 23 degrees Taurus, which would be in the 8th house. Hope this clear. Now, if a malefic planet is associated with the 22nd Decanate then a serious health problem would arise. I'll write about medical astrology in more detail in a separate article.