Brihat Samhita
सूर्यात्सप्तमराशौ यदि चौदग्दक्षिणेन नातिगतः । चन्द्रः पूर्वाभिमुखश्छायां और्वीं तदा विशति ॥ ५-१० ॥
When the moon, whose course is always from west to east, is due opposite to the sun swerving neither much to the north nor to the south, she enters the shadow of the earth.
english translation
sUryAtsaptamarAzau yadi caudagdakSiNena nAtigataH । candraH pUrvAbhimukhazchAyAM aurvIM tadA vizati ॥ 5-10 ॥
hk transliteration by Sanscript