INDIAN LUNI-SOLAR ASTRONOMY chapter on - or the first visibility of the crescent. It is thus clear that the practice was to observe the Moon when very near the Sun. 110 Again Aryabhaṭa says that 'वन्दयोगार प्रसाधितश्चैन्दुः', "the Moon was determined from her conjunctions with the Sun." The Moon was observed by him at the time of solar eclipses, or at the time of the first visibility of the crescent. Even up to the time of Prthudaka, the accuracy in lunar astronomy was chiefly aimed at the time of cclipses. Thus in his commentary on the Khandakhadyaka IV. he makes the following introductory remarks :- "All knowledge relating to (luni-solar) astronomy is desired by the wise (or cultured) specially for knowing the right instants of opposition or conjunction; these instants are, however, not visible to the eye. Of other things such as tithis, nakṣatras and Karanas, as the planets, the Sun and the Moon, are not clearly observed, their beginnings and ends are not visible. Men see the agreement between calculation and observation at the times of solar and lunar eclipses. Hence the word of the astronomers is esteemed amongst men even in respect to such things as tithis. etc."1 Thus the chief aim of the ancient Indian astronomers was to calculate the eclipses accurately and the Moon was observed chiefly at lunar or solar eclipses, though the time for observation related also to the finding of the first visibility of the crescent. This latter phenomena did not perhaps lead them to directly observing the Moon's position at such times by using instruments. Moon's Mean Motion The practice of observing the Moon at the time of the eclipses alone led to the determination of the synodic month with the following results :- (i) Mean synodic month according to the Aryabhatiya 1577917500 57753336-4320000 -days, =29.530582 days. 1. नाहुल्येन पर्व्वज्ञानार्थ सकलं ज्ञानमिष्यते शिष्ः। तेषां च पर्वाच्या दर्शनं नारिस | अन्येषामपि तिथिनक्षत्रकरणानां तस्मात् तेषां शशिभास्करयोरव्यक्तिस्मात् । शशिभास्कर- अधणयोध् ग् गणितक्यं लोकः पश्यति । तस्मात् तिथ्यादिष्वव्यर्येषु दैवहं वाक्यं लोके आद्रियते ।
