ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

CONCORDANCE OF WORKING RULES 303 since the beginning of mean Caitra up to the mean sunrise on the current lunar day. Like wise m months + d days + (ii) - (iv) denotes the time in mean solar months, days, ghaṭīs etc. elapsed since the beginning of the current mean solar year up to the mean sunrise on the current lunar day¹. Let M, D, G, V, and P denote respectively the mean solar months, mean solar days, mean solar ghaṭīs mean solar vighaṭīs and mean solar pravighaṭīs elapsed since the beginning of the current mean solar year up to the mean sunrise on the current lunar day. Then evidently mean longitude of the Sun = M signs, D degrees, G minutes, V seconds and P thirds. = (m signs and d degrees) + [minutes, seconds etc. corresponding to (ii)] - [degrees, minutes etc. corresponding to (iv)]. and mean longitude of the Moon = 13 [m signs and d degrees + (minutes, seconds, etc. corresponding to (ii)] - [degrees, minutes etc. corresponding to (iv)] because [(1/12) mean longitude of the Moon - mean longitude of the Sun. = m signs + d degrees + (minutes, seconds etc. corresponding to (ii)] (This equality is based on the fact that the left hand side denotes the mean lunar date also known as madhyama tithi). A similar rule of these calculations of the mean longitude

1. Because (iv) is equal to fraction of a lunar month between the beginning of Caitra and the beginning of the current mean solar year fraction of an intercalary month corresponding to the tithis elapsed up to the beginn- ing of the current mean lunar day since the beginning of Caitra fraction of an intercalary month corresponding to the avamaśeṣa, i.e., the lunar portion between the beginning of the current lunar date and the follow- ing sunrise.