Is the traveler's diligence in determining the Qibla at dawn an excuse for him in his prayer if he prayed facing a direction other than the Qibla, and is he required to repeat it as a traveler or as a resident if he is not excused?

If a person is unable to determine the Qibla by looking at the mihrabs (prayer niches) or by asking knowledgeable people, there is no harm in relying on modern means such as a Fajr or Asr prayer clock. Some scholars have issued fatwas permitting this, and in fact, it may become obligatory to act upon them if no other evidence is found. If a person uses these means and it later becomes clear that they were mistaken, they are not obliged to repeat the prayer, because they did what was within their capacity. This is the relied-upon opinion among the jurists. However, if they repeat the prayer as a precaution, it is more absolving of responsibility, and they should repeat it fully, not shortened.