300 BRAHMAGUPTA'S ASTRONOMY: ITS HIGHLIGHTS +13 (Sun's mean longitude) This expression may be rearranged to get the mean longitude of the Sun from the mean longitude of the Moon¹. Mean longitude of the Sun 1 [mean longitude of the Moon (intercalary months in a yuga)×ahargana revolutions] civil days in a yuga Calculating the Mean Longitudes of the Sun and the Moon without using Ahargaņa Bhaskara I follows the method of Aryabhata I and the same method more or less has been adopted by Brahmagupta in calculating the mean longitudes of the Moon and the Sun without the use of ahargana. The method may be described thus : Reduce the years elapsed since the beginning of kali- yuga to months and add to them elapsed months of the current year. Then multiply the sum by 30 and add the product to the number of lunar days elapsed since the beginning of the current month. Multiply that sum by the number of intercalary months in a juga and divide by the number of solar months in a yuga reduced to days; the quotient denotes the number of intercalary months elapsed. The remainder is the adhimasaseşa, Multiply the complete intercalary months thus obtained by 30 and to the product add the number of solar days elapsed since the beginning of kaliyuga: then multiply that sum by the number of omitted lunar days in a vuga and divide by the number of lunar days in a yuga; the remainder obtained is the avamašeşa called ahnika. Then multiply the avamašeşa 24 1. कुसुद्धतीनां सुहृदोऽथवाऽऽगतं विशोभ्य शेषस्थ लवस्त्रयोदशः । स मध्यमाकों गाकैर्निरूप्यते गुरुप्रसादात्प्रति बुद्ध बुद्धिभिः ।। MBh. I. 11-12 2. By the number of solar days here is meant the number obtained above by reducing the years elapsed since the beginning of kaliyuga to months, then adding to them the number of months elapsed since the beginning of the current year, then multiplying the sum by 30, and then adding to the product thus obtained the number of lunar days elapsed of the current month.
