The orientation of Trajan's town of Timgad
  An equation, generally used for solar energy applications, can be applied to archaeoastronomical calculations to determine the day of foundation of ancient towns. The equation is that giving the sunrise amplitude, and, the direction of the sunrise on the day of foundation was sometimes used to determine the main street of the town. Here we discuss the case of Timgad, a town founded by the Roman emperor Trajan. Probably, Timgad was founded during the first decade of September. 
Amelia Carolina Sparavigna
physics.hist-ph