Asalaamu Calaikum wr wb akhee first of all I hope everything is fine with and that allah(swt) has been generous to you The respected Uluma ikraam have decided together that the last third of the night (which is just before fajr when the tahajud is best prayed) is atleast an hour before fajr....so insha allah keep this in mind Baarakalaahu Fiikum wa laka Wa Bilaahi tawfiiq