Question: When does the time of morning prayer start and end? And at what time to make the morning prayer is preferred?
Answer: The beginning of the morning prayer "Al-Fajr" - the time of appearance of the "second Fajr", ie second dawn , it ends with the sunrise.
The preferred time of the morning prayer - it's the end of its time, during the "Isfar" (when strongly brighten, it's about 20-30 minutes before sunrise).
The Messenger of Allah (peace be upon him) said:
أسفروا بالفجر فانه أعظم للأجر
"Offer the fajr prayer in good light. There is more reward in that".
From the book "Tuhfatul - Fuqaha" (prayer book) Alyauddin Samarkandi (رحمه الله), page 102.