The Sage said — After ascertaining the rasi, amsas etc., of the Sun at the time of birth, the longitude of the Sun (Surya spast) should be worked out for the next day after the number of days taken by the Sun after entering into the rasi which will be equal to the expired amsas of the Sun. Then the difference between the longitudes of this rising Sun and the Sun at the time of birth should be converted into kalas and multiplied by 60. The product should be divided by the Surya spast converted into kalas. The Ghatikas etc., so becoming available will represent the Istakala of the birth before and after sunrise. If the longitude of the Ista Sun be more than that of the rising Sun, the Istakala of the birth will be so much after the sunrise. If the longitude of the Ista Sun be less than that of the rising Sun, the Istakala of the birth will be so much before the sunrise.

कलीकृत्य स्वषण्निघ्नं स्फुटार्कगतिभाजितम्‌ । लब्धं घट्यादिमानं यत्‌ तावान्‌ सूर्योदयात्परम्‌ । ।15।। कलादि सूर्यान्तर को 60 से गुणा कर उसमें सूर्य की गति कला से भाग दें । जितनी घड़ियाँ मिलें, उतना ही सूर्योदयादिष्ट जन्म समय होगा ।