In Vedic Astrology the Navamsa or 9th Harmonic chart (D9 chart) is said to be a microscopic view of the 9th House and therefore the hidden undercurrent of our fate. It is basically to predict marriage life of the native, spouse and life in later stage (after 32 years). The rasi chart (D1 chart) is your physical existence, the circumstances you live in, the things you do. The D9 chart is the hidden force, invisible hand of destiny that decides the results of your deeds. D9 chart basically gives information about your inner personality. The D1 chart gives information about your surface personality. The inner personality keeps on changing until late twenties and remains almost the same after that. So, its advisable to consult D9 chart in the later stage of life. Note : There are no concepts of degrees and nakshatras in D9 chart.

How to read D9 chart: Analyze the position of D9-ascendant lord in D1 chart.
This will tell you what role the native will take to pursue his nature.
Analyze the strength, placement, conjunctions of Chara Atmakaraka and Amatyakaraka in D9 chart.
Venus is the natural atmakaraka in D9 chart. Hence, don’t forget to analyze the strength, placement, conjunctions of venus in D9 chart.
Analyze the strength, placement, conjunctions of the D1-9th lord in D9 chart.
D9-chart is also used for marriage predictions.
Determine the 7th house lord in D1 chart. See the placement of D9-ascendant lord in D9 chart.
This will show how the native inherently behaves with his/her spouse.
If it is placed in 6th house: native will tend to fight with his/her spouse.
8th house: native will hide the things from his spouse and will not be transparent.
12th house: The native would be indifferent for his or her spouse.
See the placement, strength, conjunctions of the D9 ascendant lord in D1 chart.
This will give you the information about, how the native behaves with his spouse in front of the whole world.
Spouse should be seen from 7th house of D9 chart. How will he/she behaves with the native.
D9-ascendant aspected by a benefic can give a happy married life.
D9-ascendant lord aspecting D9 is a good combination for a peaceful married life.
If D9-ascendant happens to be 9th or 12th to the D1-ascendant, physical needs may be very high.
If D9-ascendant is associated with many malefics, there could be extra-marital relationships.
If the lord of 3 or 6 or 7 or 10 is posited in the 7th to D9-ascendant your spouse may have a career in law.
Venus in the 7th to D9-ascendant indicates disharmony in marriage.
If the lord of 7th in D1-chart is in 6 or 8 or 12 to D9-ascendant, married life may not be pleasant.
Conjunction of Moon and venus and if one of them is debilitated, there will be no happiness from marriage.
If the 5th from the D9-ascendant is occupied by Jupiter and venus, you could get ravishing beauty as your wife.
If the 7th happens to be the house of saturn and if malefic are in it, the spouse could look old or it could be a second marriage.
If venus is in the amsa of Mars or in the house of saturn without any benefic aspect, there could be sexual perversions.
If the 7th lord conjuct with the 6th lord and also venus, there will be separation or divorce.