215 SOLVED EXAMPLES ponding to the Moon's equation of the centre¹ to the resulting lunar days (and ghatis) in the same way as it is applied to the Moon's longitude. (The lunar days thus obtained are the true lunar days which have elapsed at sunrise since the beginning of the current month). The ghatis obtained above denote the elapsed portion of the current lunar day in terms of ghatis. Multiply those ghatis by 60 and divide by one-twelfth of the difference between the true daily motions of the Sun and Moon, in degrees : the quotient denotes the true time in ghatis (which has elapsed at sunrise since the beginning of the current lunar day).³ Let the mean lunar years, etc., elapsed at sunrise be a years, b months, c days, and d ghatis; and let the mean intercalary years, etc., elapsed at sunrise be a' years, b' months, c' days, and d' ghatis. Then the mean solar years, etc., elapsed at sunrise are (a-a') years, (b-b') months, (c-c') days, and (d-d') ghațis. The mean longitude of the Sun is therefore equal to (a-a') revolu- tions, (b-b') signs, (c-c') degrees, and (d-d') minutes. The longitude of the Sun's apogee being 2°18', the Sun's mean anomaly is equal to (b-b') signs, (c-c'-2) degrees, and (d-d'-18) minutes. Suppose that the Sun's equation of the centre derived from the above Sun's mean anomaly is m minutes. Then we subtract m/12 ghatis from or add the same amount to c days and d ghatis obtained above, according as the Sun's equation of the centre is additive or subtractive. Thus we get c days and (dm/12) ghatis. 1 To obtain the Moon's equation of the centre, the mean longitude of the Moon may be obtained as follows: Multiply the mean lunar days, etc., (corresponding to the ahargana) by 12, convert the resulting days etc. into months, etc., and add to them the mean solar months, etc., (corres- ponding to the ahargana); treat the months, etc., thus obtained as the signs, etc., of the mean longitude of the Moon. 2 A similar rule occurs in Br.Sp.Si, xiii. 23-25 and ȘïŠe, iii, 72-74.
