||In a time of urgency, you can pray anytime after dawn with Teffilen, which is 72 minutes (Shaah Zemaniyot) before sunrise. Just don't make a Blessing on the Teffilen until Misheyakir, which is when it begins to get light out. The ideal earliest time to pray and also best time is to say Shema before sunrise and start the Amida/Shemonah Esrey exactly 2 minutes after the listed sunrise. The listed sunrise is based on the beginning of the sun rising above the horizon. After 2 minutes the entire sun appears. That is the sunrise that we follow.