Surya Siddhanta
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उदयास्तविधिः प्राग्वत् कर्तव्यः शीतगोर् अपि। भागैर् द्वादशभिः पश्चाद् दृश्यः प्राग् यात्य् अदृश्यताम्॥
For the moon too, the calculation of rising (udaya) and setting (asta) is to be done as before. If located at twelve degrees west, it (the moon) is visible and if located at twelve degrees east, it becomes invisible.
english translation
रवीन्द्वोः षड्भयुतयोः प्राग्वल् लग्नान्तरासवः। एकराशौ रवीन्द्वोश् च कार्या विवरलिप्तिकाः॥
Add six signs to the longitudes of the sun and moon respectively, and find, as in former processes, the ascensional equivalent, in respirations, of their interval (lagndntardsavas) : if the sun and moon be in the same sign, ascertain their interval in minutes.
english translation
तन्नाडिकाहते भुक्ती रवीन्द्वोः षष्टिभाजिते । तत्फलान्वितयोर् भूयः कर्तव्या विवरासवः॥
Multiply the daily motions of the sun and moon by the result, in nadis, and divide by sixty ; add to the longitude of each, the correction for its motion, thus found, and find a new their interval, in respirations.
english translation
एवम् यावत् स्थिरीभूता रवीन्द्वोर् अन्तरासवः। तैः प्राणैर् अस्तमेतीन्दुः शुक्ले +अर्कास्तमयात् परम्॥
And so on, until the interval, in respirations, of the aun and moon is fixed : by so many respirations does the moon, in the light half-month (shulda), go to her setting after the sun.
english translation
भगणार्धम् रवेर् दत्त्वा कार्यास् तद्विवरासवः। तैः प्राणैः कृष्णपक्षे तु शीताम्शुर् उदयम् व्रजेत्॥
Add half a revolution to the sun's longitude, and calculate the corresponding interval, in respirations : by so many respirations does the moon, in the dark half-month (krshnapaksha), come to her rising after sunset.
english translation