Al-Biruni (440h) said: "The Fajr is at 18 degrees".

His name is Abu Rayhan Muhammad ibn Ahmad al-Biruni. He died in the year 440 after the Hijrah (1050). He is a great scholar and astronomer. And he is called the father of modern geodesy. Out of his 146 books, he dedicated 95 to astronomy, mathematics, and geography.

In his book "al-Qanoon al-Masoudi," he wrote:

"... and this is the dawn (Fajr), which has three types: the first is sharp, elongated, upright, known as the false dawn (Al-Fajr Al-Kadhib) and also called 'the tail of the wolf' (Dhanab al-Sarhan), and it is not related to any religious laws (Shari'a) or official customs. The second type is flat, spread across the width of the horizon, round like a semicircle, lighting up the world, making animals and people active for their routines and to which the conditions of worship (Ibadah) are attached. The third type is a redness that follows and precedes the sun, and it is like the first in terms of religious law... and depending on the need for dawn (Fajr) and dusk, the scholars of this science made their observations and derived from them the laws of time, that when the sun dips below the horizon and this amounts to eighteen parts, this is the time of dawn (Fajr) in the east and the time of dusk in the west, and when it was not something specific but rather mixed, there were disagreements in this law (Comment: meaning the transition from Fajr Al-Kadhib to Fajr al-Sadiq, some recognized the true Fajr later), so that some saw it as seventeen parts."