Differences in moonrise times and fasting based on the sighting in a country within the Kingdom

Question:
He says: 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 do not fast except based on the moonrise in this location”? And what is the distance at which moonrise times differ?

Answer:
The distance at which moonrise times differ is known by astronomers; it requires study. However, everyone in Saudi Arabia is required to fast because they are under one Imam, and it is not permissible for them to differ while under one Imam. This was the case when there were no means of communication, in the early period when there were no means to convey the sighting of the crescent, such as towers, radio, or rapid means of communication; it was only by means of mounts at that time. Yes, because those in Najran could not fast based on the sighting in Riyadh due to the disconnection of means. But now that means of conveying the news of the crescent have emerged, all the people of the Kingdom are required to fast because they are under one command and under one Imam, and the news has reached them. Generally, the moonrise time does not differ for them, as the Kingdom is geographically close.