See Fig. 7. AB is the ecliptio; S is the centre of the shadow for the time ofopposition, the circle around S being the circumference of the shadow CD is the Moon's orbit relative to the shadow centred at S, and Mis the posi tion of the Moon at the time ofopposition (CD, is drawn through M para Fig.7 the parsa-stiyardha could be obtained at once by considering the triangle M'L'S, right-arngled at L. But the Moon's latitude for the time of the first contact (viz. M'I') itself depends on the knowledge of the spor50-ऽthiyardha. Hence we use the method of successive approximations. To begin with we neglect the variation of the Moon's latitude and take MS as the Moon's latitude throughout the eclipse. Thus we take M, to be the position of the Moon for the time of the first contact. where Let M,[1 be the perpendicular to the ecliptic. Then from the triangle 7 and MS=half the sum of the diameters of the Moon and the shadow (1) . gives LS, i.e., the distance along the ecliptic to be traversed by the Moon with respect to the shadow during the baा50-ऽthijardlha. Thus if mr denote the daily motion of the Moon with respect to the shadow, then ia (1) . 1 Neither the ecliptic mor the Moon's orbit is a straight ime but their arcs which we are considering are so small that they may be regarded as such without much error.
