The Zodiac is a circle having 360 degrees. lt has twelve spokes, each at a distance of thirty degrees. The 108 Navamsas are fixed in that circle. The four groups of movable and fixcd signs starting from Mesha stand for the east and other principal directions of the compass. The four common signs starting from Mithuna respectively represent the south-east, south-west, north-west, and north-east. The exact longitudes of the planets at that time have to be entered in their Rasis and Navamsas.