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.

पूर्वं जन्मेष्टकालो हि क्रमाज्ज्ञेयो विपश्चिता । साधितौदयिकादर्कादिष्टेऽर्केऽधिकहीनके । ।16।। यदि इष्ट सूर्य औदयिक सूर्य से कम हो तो सूर्योदय से उतनी घड़ियाँ पहले तथा इष्ट सूर्य अधिक हो तो उतनी घड़ियाँ बाद में जन्म होता है । सारांश में पूर्व प्रकार से प्राप्त सूर्यस्पष्ट के गतांशादि जिस समय होते दिखें, उसी समय जन्म होता है ।