पृष्ठम्:महाभास्करीयम्.djvu/२१५

130 the following order : TRUE LONGITUDE OF A PLANET (1) the longitude correction. (2) the bhujantara correction (i.e., the correction due to the Sun's equation of the centre). (3) the bhujaphala correction (i.e., the Moon's equation of the centre). (4) the correction due to the Sun's ascensional difference. In later works, two more corrections are prescribed for the Moon. The one is equivalent to (i) the deficit of the equation of the centre of the Moon plus (ii) the evection¹, and the other is what is now called "the variation". The former occurs for the first time in the Vatesvara-siddhanta of Vateśvara (904 A.D.) and the Laghu-manasa of Manjula (932 A. D.) and the latter in the Bijopanaya of Bhaskara II (1150 A.D.). The next six stanzas relate to the calculation of tithi, karaṇa, and nakṣatra, which are three out of the five principal elements of the Hindu Calendar, the other two being yoga and vāra (week-day), and to the pheno- mena of vyatipāta. The calculations for tithi, karana and naksatra are made for sunrise. Calculation of the tithi: 31-32. Divide the true longitude of the Moon as diminished by that of the Sun by 720 minutes (of arc); the quotient (obtai- ned) denotes the number of tithis (elapsed). Multiply the re- mainder by 60 and divide (the product) by the difference bet- ween the (true) daily motions of the Sun and the Moon: then are obtained the ghatis, vighatis, and asus (elapsed of the current tithi). (The time in ghatis, vighatis, etc. of) the current tithi to elapse or elapsed is measured from sunrise. A lunar (or synodic) month is defined in Hindu astronomy from one new moon to the next. There are thirty tithis (lunar days) in a lunar month. The first tithi begins at new moon (when the Sun and the Moon have the same longitude) and continues till the Moon, due to her rapid motion, is 12° (or 720') in advance of the Sun; the second tithi then begins and continues till the Moon is 24° in advance of the Sun; the third tithi ¹ See my paper entitled "The evection and the deficit of the equation of the centre of the Moon in Hindu Astronomy" in Bull. Banaras Math, Soc., Vol. VII, No. 2, 1945. This rule occurs also in Susi, 66; BrSpSi, ii. 62; KK (Sengupta's edition), i. 25; SiDV, I, ii. 22; Sise, iii. 71; SiSi, I, i. 66.