Differences in moonrise times within a single country

Question:
I say: Honorable Shaykh, may Allah grant you success, is it permissible for someone in the Saudi state, for example in Najran or the Eastern Province, to say, "I will not fast except upon seeing the moonrise in this location"? And what is the distance over which moonrise times differ?

Answer:
Those who know the places where moonrise times differ are the astronomers; it requires study. However, everyone in Saudi Arabia is bound by the announcement, because they are under one Imam. Therefore, it is not permissible for them to differ, as they are under one Imam. This was the case when there were no means of communication; the initial situation lacked means to convey the sighting of the crescent, such as radio, television, or other media. At that time, it was only via mounts, yes, because they could not be in a position to see the moon in Riyadh due to the lack of communication channels. But now, since means of conveying the crescent sighting have emerged, all the people of the Kingdom are required to fast, because they are under one command, under one Imam, and the news has reached them. Generally, the moonrise time does not differ for them, as it is a close kingdom.