*He also quotes Rabbi Tukachinsky who held like the opinion of 90 minutes.
*[http://www.yutorah.org/lectures/lecture.cfm/728553/Rabbi_Hershel_Schachter/Shiur_on_Zmanim_in_Halacha Rav Hershel Schachter on yutorah.org] (min 65-7) says that we assume that [[Olot HaShachar]] depends on degrees below horizon and the specific times vary according to one’s location. Similarly, [http://www.ou.org/webcast_kosher Rav Yisrael Belsky] (OU Kosher Webcast, 2011, min 19-21) mentioned in passing that [[Olot HaShachar]] is assumed to be 72 minutes before sunrise, varying according to the longitude and latitude.</ref>
# According to Sepharadim, Alot HaShachar is 72 minutes before sunrise,
and these minutes are proportional to the length of the day.<ref> Yalkut Yosef, Kitzur Shulchan Aruch, Siman 58, Seif 3 </ref>