Is    there a certain length of time that the new moon has to be in the sky?
Question

What is the method of confirming the beginning of every lunar month? Is there a certain length of time that the new moon has to be in the sky?
Praise be to Allah.The saheeh ahaadeeth reported from the Prophet (peace and blessings of Allaah be upon him) indicate that when the new moon is seen by a trustworthy person after the sun has set on the thirtieth night of Sha’baan or the thirtieth night of Ramadaan, this sighting is considered to be valid, and the first of the month is established without any need to consider the length of time that the moon stays in the sky after sunset, whether twenty minutes or more or less. There is nothing in the saheeh ahaadeeth to indicate how long it should take for the moon to set after the sun has set.