question #3 Sahih Muslim 1094c, Book 13, Hadith 52 : What visual signs should one look for in the sky to determine the correct time to stop eating before fasting?

The Adhan of Bilal may not mislead you with regard to your food at the commencement of the fast, nor the vertical (streaks) of whiteness in the horizon (for it is an indication of false dawn). You should stop eating (food) till (the whiteness) spreads like it. Hammad narrated it and with the gesture of his band he explained, the horizontal position (of the streaks of light).