There is an angle of approximately five degrees between the plane of the lunar orbit and the ecliptic plane. Once each revolution, of the moon the Sun, the earth and the moon become aligned with one another, the Sun and moon sharing the same orientation with respect to the earth. This state of collinearity is called Ijtimâ’i neyyireyn = Conjunction. In this state the face of the moon in our direction becomes obscure. We cannot see the moon. This period of time is called Muhâq (Interlunar Period, Dark Moon, or Dark of the Moon). There is not a fixed length of this period of muhâq. It varies from twentyeight hours to seventy-two hours. The Ottoman calendars give a maximum of three days. The time of conjunction is exactly the middle of the period of muhâq. Scientific calendars provide monthly tables showing the variations in its length. Since the earth revolves about the Sun, too, the duration of time between two conjunctions is 29 days and 13 hours. At the time of conjunction, the Sun and the moon pass the meridian at the same time. The moon can by no means be seen anywhere before the angle between the Sun and the moon as seen from the earth, which is termed Beynûnet (elongation), has become eight degrees [approximately fourteen hours after the moment of conjunction]. When the angle becomes eighteen (18) degrees maximum, the moon comes out of the state of invisibility and the new moon appears on the western horizon within the forty-five minutes during sunset. However, due to the fifty-seven minute lunar parallax[1], when it reaches a position five degrees above the horizon, it can no longer be seen. After the moon comes out of the state of invisibility, the new moon can be observed in places situated on the same longitude as the location where the sunset is taking place. As for later hours, or, at night it can be observed after sunset in countries west of these places.

The fast has three fards:

1. Niyya (to intend);
2. To know the earliest time of the niyya, as well as its latest time;
3. To fend off the things that will break the fast starting from dawn (fajr sâdiq) up to sunset, [that is, within the shar’î daytime].