Answer: Sighting of the new moon is ascertained by knowledge of the actual sighting or through solid news of such sighting, or some other means. Certainty can also be achieved through common knowledge. Amongst other sources of ascertaining the sighting of the new moon is the lapse of thirty days on Sha’ban’s crescent for the start of Ramadhan to be confirmed, or thirty days on the crescent of Ramadhan for the new moon of Shawwal to be confirmed [and so on]. Sighting can also be confirmed by the evidence of two witnesses of impeccable character (adl).
However, sighting of the new moon is not recognised by the evidence of women, or by the evidence of one just witness, even with oath, or by the words of astrologers. Neither by its absence after dawn dusk, so that it could be said that it belongs to a previous night, nor by the evidence of two just witnesses, if the evidence is not confined to their own sighting of the newly born moon. Sighting is not recognised too when it is seen before zawaal so that the day of sighting be from the ensuing month. The impression of a ring it may give, proving that it could belong to a previous night, cannot be accepted as well.

Answer: The evidence could be one or more of the following:
1. You have sighted it yourself (without binoculars or a telescope).
2. The testimony of two men of impeccable character, provided that you do not have any knowledge of instances that they may be wrong, and that you do not dispute their testimony.
3. The lapse of thirty days on the month of Sha’ban, thus reaching certitude that Sha’ban has come to an end and that Ramadhan shall commence.
4. When the news of the birth of the moon of Ramadhan becomes commonplace that you are sure of the sighting.