Time for Fajr Prayers

Just before dawn a column of whiteness rises upwards from the east. It is called the first dawn. When this whiteness spreads, it is called the second dawn, and the Prime time for Subh prayers. The time for Subh prayers is till sunrise.

Rules Regarding Namaz Times

A person can start offering prayers only when be becomes certain that the time has set in or when two just (Adil) persons inform that the time has set in. In fact, one can rely upon the Adhan, or on advice of a person who knows the timings and is reliable.  

If a person cannot be certain about the Prime time for prayers due to a personal handicap like blindness or being in the prison cell, he should delay the prayer till such time when he feels sure that the time has set in. And as an obligatory precaution, he should act the same way when there are general hindrances like dust or clouds. 

If a person is satisfied on the basis of any one of the above methods that the time for prayers has set in and he begins offering prayers, but then realises during the prayers that the time has not yet set in, his prayer is void. And the position is the same if he realises after the prayers that he has offered the entire prayers before time. However, if one learns as he prays that the time has just entered or if he learns after the prayers that the time entered while he was in the process of praying, his Namaz will be valid.  

If a person is heedless of the fact that he should pray after ensuring that the time has set in, and if he realises after the prayers that he had offered the entire prayers in time, his prayer is in order. And if he realises that he had offered his prayers before time or does not realise whether he had offered the prayers within time or not, his prayers will be void. In fact, if he realises after offering prayers that the time for prayers had set in while he was praying, he should offer that prayers again. 

If a person was certain that the time for prayers had set in, and began offering prayers but while praying, he doubted whether or not the time for it had actually set in, his prayers would be void. However, if he is certain while offering prayers that the time for it has set in, but doubts whether what he has already performed in the prayer, has been in time or not, his prayer is valid.  

If the time left for Namaz is so little that if we perform some Mustahab acts of the prayers, an obligatory part of the prayers will fall beyond the prescribed time, one should not perform those Mustahab acts. For example, if on account of reciting qunut a part of the prayers will lapse beyond time, one should do without qunut.