The Navamsha – 9th divisional chart or Varga
In Hindu astrology the horoscope may be broken down into several vargas, or divisions. Although as many as 16 basic divisional charts exist, most astrologers only concern themselves with the navamhsa or 1/9 division. Each varga chart relates to a certain house, and this one corresponds to the 7th, the house of marriage. However, because the 7th is the opposite of the lst, which is the most personal part of a horoscope, it has to do with a person's relationship to society and all its functions. Therefore the navamsha is of great importance, and no professional Hindu astrologer will attempt to analyze a birth chart without it.
Although astrologers consult the navamsha for specific details of married life, the chart is mainly used for its impact on a person's life in general, for this chart carries a good deal of power to affect the actual birth chart. For example, if 4 or 5 planets in the navamsha are exalted, or in their own signs, the original horoscope is tremendously strengthened in a recognisable way. Naturally, if many planets are fallen in this divisional chart, the opposite results would occur. Also, nearly all Hindu scriptures are emphatic about the fact that if a planet is exalted in the birthchart but fallen in the navamsha, then the particular effects of that planet will be extremely mixed, and in that planet's dasha (planetary period- will discuss later) some amount of misery must be reaped. It should also be mentioned that the Hindu scriptures are replete with planetary combinations and formulas involvng this varga. One such basic and easily noted condition is what is known as vargothamamsa, or vargottama. This occurs when a planet in the navamsha occupies the same sign as its horoscope placement. This is a beneficial situation, and Hindu scriptures state that the planet will give results similar to those given when posited in its own sign. A planet in its fallen sign, being vargottama, is of course only worse off.
One must bear in mind, however. that the navamsha is not an actual horoscope but a calculated one based upon the original. Therefore aspects and conjunctions in this chart should never be used, despite the fact that some astrologers attempt to do so. Also, planets are posited in signs in the navamsha, but there are no degrees for them.
The navamsha is essentially used to color the actual horoscope. There is no question that specific results can be delineated from the proper use of the chart, but the conditions revealed must be balanced with the natal horoscope. For example, if Jupiter is fallen in the 10th house of the navamsha, one may expect disturbances in the person's career. However, the intensity of difficulties will depend upon the condition of the 10th house of the actual birth chart.
There is one consideration, especially for Westerners, which must be taken quite seriously. And that is that when a 30 degree sign is divided into 9 parts, each one is only 3 degrees 20 minutes. Therefore since 1 degree equals 4 minutes of arc, an error of 13 minutes in the birth time throws this chart completely off. In many cases a mere 4 or 5 minute discrepancy will give a wrong ascendant for the navamsha. Thus, it is Inappropriate to use the houses in the navamsha unless one is certain the birth time is exact, or unless events proving the accuracy of the divisional chart have been witnessed. But although the houses may be inaccurate due to an improper birth time, the planets in signs will not be affected. Therefore even if one is not positive the birth time is exact, there is still great value in knowing what signs the planets occupy in the navamsha.
( Note: Part of the above text is from the book, Ancient Hindu Astrology for the modern Western Astrologer)