According to Sephardic custom, one who remained awake throughout the night must recite Birkot Ha'Torah after the point of Alot Ha'shahar (daybreak), and should not learn Torah once this point arrives before reciting the blessings. (Different customs exist among Ashkenazim regarding the recitation of Birkot Ha'shahar in the morning after remaining awake throughout the night, as some do not recite the blessings, whereas others do. The Mishna Berura advises one to try to listen to the recitation of Birkot Ha'Torah by somebody who had slept during the night. Sepharadim, however, recite the blessings in this case.) The Shulhan Aruch maintained that the point of Alot Ha'shahar is 72 halachic minutes before sunrise. The Vilna Gaon (1720-1797), however, disagreed, and held that this occurs already 90 halachic minutes before sunrise. Due to this difference of opinion, Hacham Ben Sion Abba Shaul (Jerusalem, 1924-1998) ruled that if somebody learns throughout the night – as is customary on the night of Shabuot, for example – he must stop learning 90 halachic minutes before sunrise, and refrain from learning until the point of Alot Ha'shahar according to the Shulhan Aruch's opinion. He should then recite Birkot Ha'Torah and resume his learning. Since learning Torah is not allowed before reciting Birkot Ha'Torah once Alot Ha'shahar arrives, and one should not recite Birkot Ha'Torah before Alot Ha'shahar, one should desist from learning during the period when it is uncertain whether the point of Alot Ha'shahar had arrived. One cannot yet recite Birkot Ha'Torah, out of concern for the position of the Shulhan Aruch, but one cannot yet learn Torah, due to the ruling of the Vilna Gaon. Hacham Ovadia Yosef, however, disagrees, and maintains that a person who remains awake throughout the night may follow the view of the Shulhan Aruch and continue learning Torah until 72 minutes before Alot Ha'shahar. He should then recite Birkot Ha'Torah and resume his learning. Moreover, Hacham Ovadia ruled that if one does not know when Alot Ha'shahar occurs, he may continue learning until he knows for certain that Alot Ha'shahar has arrived, and then recite Birkot Ha'Torah at that point. Hacham Ovadia added that one specifically should not find somebody who had slept during the night and listen to his recitation of Birkot Ha'Torah, because it is preferable to perform a Misva oneself than to discharge one's obligation by listening to another person's recitation ("Misva Bo Yoter Mi'bi'shluho"). Summary: According to Sephardic practice, one who remained awake throughout the night must recite Birkot Ha'Torah at the point of Alot Ha'shahar (daybreak), and he may not learn Torah from that point until he recites Birkot Ha'Torah. We follow the view of the Shulhan Aruch, that Alot Ha'shahar occurs 72 halachic minutes before sunrise. One who does not know when Alot Ha'shahar may continue learning until he knows for certain that Alot Ha'shahar has arrived and then recite Birkot Ha'Torah at that point.