Kūshyār al-Daylamī. Those among them who discuss sighting rely on him and others like him. Yet their accomplished specialists, such as Abū ʿAlī al-Marwadhī al-Qattān and others, rejected his claims, saying that he sought thereby to win favour among the Muslims; otherwise, this cannot be determined precisely. Perhaps anyone among them who ventured into this was suspected of hypocrisy—for hypocrisy is hardly unlikely among such people—or sought thereby to gain favour with certain ignorant kings who think highly of astronomical calculation while professing Islam.

The reason this cannot be determined precisely is as follows:

Astronomical calculation merely estimates this by determining the positions of the sun’s and moon’s discs and their courses: that they will align at such-and-such an hour, in such-and-such a zodiacal sign in the sky, above such-and-such a place on earth, whether the conjunction occurs by night or by day. This conjunction occurs after the moon disappears and before the crescent appears. The moon travels through its twenty-eight stations, as Allah has appointed its stations, then draws near the sun and disappears for one or two nights because of its alignment with it. When it emerges from beneath it, Allah places light in it. Its light then increases as it moves farther from the sun, until it stands opposite it on the night of the full moon. Then its light diminishes as it draws nearer the sun, until it reaches conjunction with it.

This is why they speak of conjunction and opposition. They cannot say, “At the time of separation, the crescent will be in such-and-such a state.” They say, “Conjunction occurs at the time of disappearance, and opposition at the time of the full moon.”