Benefit: Innovation - Relying on Prayer Schedules in Large Cities?
In the Name of Allāh, the Ever Merciful, the Bestower of Mercy
"It is well known that people who live in well-lit (large) cities can not determine the time of the entrance of Fajr by their own sighting (of the horizon). Thus, it is upon them to be cautious and go by the athān and by prayer schedules that determine the times of Fajr's entrance according to the hour and minute, acting by the statement of the Messenger of Allāh (ṣallallāhu ʿalayhi wa-sallam): "Leave what makes you doubt for that which does not make you doubt." And his statement (ṣallallāhu ʿalayhi wa-sallam): "Whoever stays away from doubtful matters will keep his religion and his honor protected." And Allāh is the Granter of success.
Source: Majmūʿ al-Fatāwī of Shaykh Ibn Bāz (15/286), may Allāh have Mercy on him