For “sighting” varies according to the elevation of the terrain, the clarity or murkiness of the atmosphere, the observer’s eyesight and its sharpness, how long or briefly one looks intently, whether one directs one’s gaze correctly, the number of people watching for the crescent, and the crescent’s thickness. It may not be visible at sunset, but afterwards its distance from the sun increases, so it grows brighter and emerges from the glare that prevents it from being seen; it then becomes visible.

Likewise, they have not agreed on a single angular measure for its visibility. Rather, their views have varied greatly, with no firm basis. The matter rests only on customary experience, which has no fixed mathematical rule. Some set the measure below ten degrees, while others set it higher. Their conflicting views on increasing or decreasing it resemble those of people who have attempted to fix the number of transmitters required for mass transmission to produce certain knowledge of what is reported. Yet there is no fixed numerical threshold for this, since knowledge depends on factors beyond numbers, just as sighting does.

All of this applies if the crescent is understood as that which has appeared in the sky, and complete cloud cover is treated as creating uncertainty. But if the crescent is understood as that which people have sighted and perceived, which has become visible to them and whose appearance they have announced aloud, this difficulty disappears in every case. The disagreement over this is well known among scholars within the school of Imam Ahmad and others. The second view is that of al-Shāfiʿī and others. And Allah knows best.