Relying on Astronomy or Sighting for the Entry of the Month of Ramadan

Question:
He says: Honorable Shaykh, may Allah grant you success. We have a doctor at the university who says that the criterion for the entry of the month of Ramadan is the sighting, but we rely on astronomy to deny the entry of the month. So, is…?

Answer:
If it has become based on the sighting, then if we rely on astronomy, it is not based on the sighting. We rely on the sighting and do not rely on astronomy, because the Messenger of Allah (peace and blessings be upon him) commanded us to rely on the sighting, so we do not contradict the command of the Messenger of Allah (peace and blessings be upon him). Then, who among the astronomers knows astronomy and masters it?
There must be error among the astronomers; they are not infallible. But there is no error in the sighting. The sighting is the sighting, that is all. Why? Seeing is not like hearing. The sighting with the naked eye has no doubt in it. But calculation errs and hits the mark because it is human work. This is from one aspect. The other aspect, which is more important, is that the Messenger did not command us to rely on calculation. Yes.