The Salaat timing are provided by the Office of the Supreme Religious Authority (Marja’iyya) in Najaf al-Ashraf via I.M.A.M. office in Dearborn.
Please use the link below to read their explanation on determining salaat timings.
Link to I.M.A.M. prayer times page:
Link to prayer times/qibla direction based on Astronomical Research Center linked to the Marja’iyya.
https://english.nojumi.org/prayertimes