293 BRAHMAGUPTA'S ASTRONOMY ITS HIGHLIGHTS I as the remainder. we subtract one from it, and get 1,850,569 as the correct ahar gana for the day. An Alternative Rule for Ahargana Both Bhāskara I and Brahmagupta give an alternative rule for calculating out ahar gana : Multiply the number of (solar months ) elapsed since the beginning of kaliyuga by the number of lunar months (in a yuga) and divide by the number of solar months (in a yuga). Reduce the quotient to days (and add the number of lunar days elapsed since the begin- ning of the current lunar month); then multiply by the number of civil days ( in a yuga) and divide by the number of lunar days (in a yuga); the quotient denotes the ahargana. Mean Longitude of a Planet (i) The mean longitude of a planet in revolutions is given by the expression: (Brahmagupta and also Bhaskara"). 1. शशांकमा सैरभिताडितान इरेदतीतमासानर्थ वार्कसम्भवैः । दिनीकृतान् भूमिदिनैर्हतान् दिनैविभज्य लब्धश्शशिजैरहग णः || युगगतशशिमासवधाद्रविमासाप्तं दिनीकृतं सविनम् | भूनिगुणितं शशिदिनहृतनाप्तमवर्गणः सैकः || 2. इष्टग्रह भगण गुणादहणात् कल्पसावन द्य हृतात् । भगव्यादि फलं मध्यो लंकायां भास्करौदयिकः ।। MBh. 1.7 --BrSpSi XIII. 18 BrSpSi. I. 31 3. उदारितान् यान् भगवान् क्षमादिनैलंभामहे कान् कलियातवासरैः । इति प्रलब्धा भगवास्ततः क्रमाद् गृहांशलिप्ता विकलाः सतरपरा ! पर्यावरणान्यासो हियते भूदिनैस्ततः । लभ्यते पर्ययाः शेषाद्राशि भागकलादयः || भास्कर स्त्रिशता षष्ट्या सङ् गुणय्य पृथक् पृथक् । तेनैव भागद्दारेण लभ्यतेऽदयावधेः || --- MBh. I. 8 -- LBh. I. 15-17 (Divide the product of the revolution-number of a planet and the ahargana by the (number of) civil days (in a yuga); thus are obtained the ( number of) revolutions (performed by that planet). From the (successlve remainders multiplied respectively by 12,30 and 60 and divided by the same divisor (i.e. the number of civil days in yuga) are obtained the signs, degrees and minutes etc. (of the mean longitude of that planet) for (mean) sunrise fat Lanka).
