Navamsha (D9) chart explained
The navamsha (D9) is the divisional chart that divides each sign into nine parts of 3 degrees 20 minutes each. It is the most used divisional chart, especially for marriage and the strength of grahas.
What it is
Each sign's nine navamsha parts run through the signs in a fixed order that depends on the sign's element. Movable signs start the navamsha count at their own sign, fixed signs at the ninth sign, and dual signs at the fifth.
How it is worked out or read
This site does not yet compute the navamsha. The rule above is the standard one, and a navamsha chart can be checked by hand from the sign and degree of each graha in the birth chart.
Where it appears on this site
The navamsha is not in the birth chart tool yet. The divisional charts article gives the wider picture.
Why the navamsha is so widely used
The navamsha, or D9, is the most widely used divisional chart. It divides each sign into nine parts of 3 degrees 20 minutes, and the classical texts consult it for the strength of the grahas and for questions of marriage. A planet that is strong in the main chart is sometimes checked in the navamsha, and a planet that looks weak in the main chart may be read more favourably there, according to the traditions that use it.
Because the navamsha is used so often, it is one of the first divisional charts that a reader learns. Its rules are standard in outline, but the details of the mapping are stated in different ways across the sources.
The mapping in outline
Each sign's nine navamsha parts run through the signs in a fixed order that depends on the sign's quality. Movable signs begin the count at their own sign, fixed signs at the ninth sign from their own, and dual signs at the fifth. A planet at a given degree of a sign therefore falls in a navamsha sign found by moving forward a set number of places from the starting sign of its quality.
The reader can apply this rule by hand once the sign and degree of the planet are known. The result gives the navamsha sign for the planet, which is then read in the same way as a sign in the main chart.
Using the navamsha with care
Because the navamsha is a finer division, its readings are sensitive to the exact degree of the planet. A small error in the birth time can move a planet across a navamsha boundary. The reader should therefore check the degree carefully, and should not treat a navamsha placement as more certain than the main chart it refines.
The navamsha on this site
The site does not compute the navamsha in its chart yet. A reader who wants the navamsha sign for each graha can apply the rule above to the signs and degrees shown in the birth chart. Until a checked table is in place, navamsha results are described as a method for the reader to apply, not as results the site has verified.