Birth Chart, Navamsha and other charts
We should always use the navamsha along with the basic birthchart.
The regular birth-chart, the sign chart or rashi chakra, is only a general chart. It remains the same for people born within the same hour or two.Sometimes it is repeated for people born the day before or after at the same hour.This is because the Moon stays in the same sign for two and a half days. For this reason, we cannot rely upon the rashi chart alone for great accuracy. For this reason, the rashi chart is not enough to allow for exact determination of physical constitution. It shows major tendencies but is at most 80% accurate.We must, therefore, examine other factors than the basic birth-chart before making primary determinations. The birth-chart shows us the general field of energies in operation but not their specific manifestations.
The navamsha Ascendant is also an important factor for determining the physical constitution (though with the generally approximate birth times we often have we cannot always be sure of it).
It is helpful to examine the degree of planets in a chart, the closeness of aspects, and the bhava or house chart along with the positions of the midheaven and nadir, which require specific degree positions.
Aspects that are nearly exact have a special power. Aspects that occur in the navamsha chart as well as in the birthchart also possess special power. Generally, the closer the aspects, the more likely they will occur in different divisional charts as well. This is particularly true for conjunctions.
Also examine the Drekkana as well as the Rashi and Navamsha for all general indications. Two people with the same Rashi but different Drekkanas have very different charts. One can generally be certain of the Drekkana even when the Navamsha itself may be in doubt because of an uncertain birthtime. The Drekkana remains the same for a period of about forty minutes, while the Navamsha changes about every thirteen minutes.