a) If the skies are not clear or are obscured due to dust, smoke, mist, etc. then the declaration of one upright Muslim, whether man or woman is sufficient.
b) If the skies are clear and no obscurity exists due to dust, mist, etc. then the testimony of even a few individuals will not be sufficient. The Khabar (information) of such a large group of people that would necessitate certainty or overwhelming assurance is required. This is required as the prevailing sky condition warrants that a large group of people sight the moon and that the sighting would not normally be limited to a few individuals.
Some Fuqahaa (Jurists) have endervoured to specify the number of individuals whose testimony would necessitate Dhann-e-Ghaalib. On the one hand, Khalf ibn Ayyoob [radhiallaahu anhu] considered the testimony of even 500 people insufficient. On the other hand, Hasan ibn Ziyaad [radhiallaahu anhu] on the authenticity of Imaam Abu Hanifa [ra] regarded the testimony of 2 males or 1 male and 2 females as sufficient. Allamah ibn Nujaym al-Misri [ra] preferred this view of Hazan ibn Ziyaad [ra] due to the apathy and negligence of the people of his time in regards to moon sighting. (Rasaail-e-ibn Aabideen vol.1 pg.234)
The reality is that this number will vary from time to time, place to place and will depend upon the qualities and attributes of the witnesses.
Furthermore, certain Ulama have asserted that the requirement of the testimony is a large group if a bid’ah (innovation) and unsubstantiated? In refutation to this, we present the narration of Musannaf Abdur Razaak (Hadith 7378)
This prerequisite is furthermore in keeping with the dictates of logic and reason. The sighting of only a few persons despite clear and unobscured skies alludes to an error or fabrication.