Both, the Rasi-chart and the Navamsa chart are deemed equally important and therefore, consulted together. Whereas the Rasi-chart provides overall information regarding the location of planets and sensitive-points such as the Lagna, the latter provides vital information regarding their active quality and strength. A planet may be well-placed in the natal-chart Rasi-wise but its full effects may not materialise if its situation in the navamsa-chart is not supportive.
Navamsa means one-ninth part of a Zodiac Sign. Navamsa literally means the “Ninth Division”. Thus, each navamsa measures 3 degrees and 20 minutes in longitude or one quarter of a Nakshatra (Constellation), and the Zodiac of Signs comprises 108 navamsas divided into four groups, 1) Mesha Aries), Simha (Leo) and Dhanus (Sagittarius)– for which signs the navamsas are from Aries to Dhanus, 2)Vrishibha (Taurus), Kanya (Virgo) and Makara (Capricorn) – they are from Makara to Kanya, 3) Mithuna (Gemini), Tula (Libra) and Kumbha (Aquarius)– they are from Tula to Mithuna, 4) Kataka (Cancer), Vrishchika (Scorpio) and Meena (Pisces) – they are from Kataka to Meena; the Lagna (Ascendant)rising or the planet situated in the first navamsa of Chara rasis(“movable signs”), in the 5th navamsa of Sthira rasis (“fixed signs”) and in the 9th navamsa of Dwisvabhava rasis (“common signs”) will be in Vargottama and hence strong.
The lords of 1st, 4th and 7th navamsa of a sign represent the Deva (“Divine beings” and constructive forces); persons born with any of these navamsas rising in the Lagna are generous, religious, wealthy, powerful and influential. Persons born in the 2nd, 5th or the 8th navamsa whose lords represent the Naras (“Human beings and their efforts) are generally kind, good natured, engaged in the pursuits of human welfare and reputed; and in the 3rd, the 6th or the 9th navamsa whose lords represent the Rakshasas (“Demonic beings” and evil forces) are selfish,cruel, violent, destructive and possess many negative qualities. Moreover, the Lagna-rasi and the Lagna-lord should not form or occupy the 6th, the 8th or the 12th bhava in the Navamsa Chart nor the lords of the 6th, the 8th or the 12th of the Rasi Chart associate with the Navamsa Lagna or its lord.
A Navamsa is equal to one-ninth part of a sign or one nakshatra-pada (onefourth part of a constellation) and is one of the Shodasvargas i.e. one of the sixteen sub-divisions of a sign that give more and more precise good or bad position of a planet or lagna-point in the natal-chart vis-à-vis other signs and sign-lords. Birth in Vargottama Lagna is considered very fortunate and planets in Vargottama are very strong and confer benefic results if they do not occupy inimical signs. The occupation of own navamsa by a planet is superior to the occupation of its exaltationnavamsa. The planet which is in its exaltation sign in the Rasi-chart but situated in its neecha-navamsa (debilitated in Navamsa-chart) produces its bad results very soon, however, a planet situated in its debilitation sign in the Rasi-chart but in its ucchanavamsa(exalted in Navamsa-chart) invariably confers auspicious results. If at the time of birth planets are placed in inimical signs even if they be in Vargottama they render all Raja yogas useless, the same is true if many planets are in debilitation. The Rajayogakarakas cease to be Rajayogakarakas if they happen to occupy their neecha-navamsas. Saturn occupying its own or exaltation sign does not afflict natural benefics or their yoga-formations provided it does not simultaneously occupy its neechanavamsa but all planets occupying navamsas ruled by Jupiter usually act as benefics and if situated in a kendra, in the 9th or in the 2nd house from the lagna make one very learned, famous and even establish a new school of thought or system. Rahu and Ketu (mythology) do not rule any navamsadivision but a navamsa of Mars is to be found in all signs.
Results of planetary periods (dashas) and sub-periods (antra-dashas) vary in accordance with the particular location of those bhava-lords in the Navamsachart. A planet otherwise strongly placed in the Rasi-chart with reference to a specific bhava or its lord does not produce in its own dasha/antra-dasha the anticipated good results relating to that bhava in full if it happens to be situated in the navamsa-chart in the 6th, the 8th or the 12th from the sign occupied by that particular bhava-lord e.g. the lord of the Lagna situated in the 3rd house in conjunction with the lord of the 3rd gives prosperous, happy and helpful brothers but if in the navamsa-chart the lord of the lagna is in the 6th, the 8th or the 12th from the lord of the 3rd then there may be enmity with brothers or sorrow to them. If the lord of the 2nd house is in conjunction with the lord of the 10th situated in the 10th house and the lord of the lagna is involved in Rajayoga one secures a high political or administrative position during the dasha/antar-dasha of the lord of the 2nd house but in case in the navamsa-chart the lord of the 2nd is in the 6th, the 8th or the 12th from the lord of the 10th then contrary results will be experienced.