What should we do if the imam of the mosque follows astronomical timings and prays Fajr before its Shari'ah time?

The Shaykh : The congregation. That is, he should go to the mosque. If they pray the obligatory prayer before its time, as we mentioned earlier, it becomes a voluntary prayer for him. Then he returns home and prays the obligatory prayer within its time, especially praying it with his family, like this. However, there is something more obligatory, but not everyone is able to do this obligatory act, which is to alert the people of the mosque to this issue, my brother. Because this is a serious matter. We read in the Qur'an a clear, decisive text, preserved by the consensus of Muslim scholars: ; that is: every prayer has a time. The time for Fajr is at the dawn of the true, white dawn that extends from the north to the south. There is absolutely no disagreement among Muslim jurists on this. Now, this ruling is being violated. Why? Because they have become entangled, Allah knows best, since when, with astronomical timings. Astronomical timings differ completely, because astronomical timings take sea level into account and give the timing for everyone at this level, whereas the situation differs between a man in a valley, a man on the slope of a mountain, and a man on the peak of a mountain. All of these people have timings that differ from one another completely. So, in conclusion, regarding your question, I advise that he pray with the congregation in the mosque. If they are praying half an hour early, he should repeat it at home in congregation. And they pray, as I said, in the mosque, which is... meaning, after the dawn has appeared, they establish the prayer, so the obligatory prayer is valid, and the Sunnah is not valid.

The questioner : May Allah reward you with good, in a follow-up.

The Shaykh: There is no power nor strength except with Allah.
Yes.