What counts as having caught the prayer
It is set at a single unit at either end of the day.
مَنْ أَدْرَكَ مِنَ الصُّبْحِ رَكْعَةً قَبْلَ أَنْ تَطْلُعَ الشَّمْسُ فَقَدْ أَدْرَكَ الصُّبْحَ
Man adraka mina-ṣ-ṣubḥi rakʿatan qabla an taṭluʿa-sh-shamsu fa-qad adraka-ṣ-ṣubḥ
Whoever catches one unit of the dawn prayer before the sun rises has caught the dawn prayer.
Where this comes from
And whoever catches one unit of the afternoon prayer before the sun sets has caught the afternoon prayer. Almost missing it and missing it are treated as different things.
The full narration
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "Whoever could get one rak`a (of the Fajr prayer) before sunrise, he has got the (morning) prayer and whoever could get one rak`a of the `Asr prayer before sunset, he has got the (`Asr) prayer
Source
Ṣaḥīḥ al-Bukhārī · 579
- Agreed upon as authentic (al-Bukhārī / Muslim)