[2] Nowruz is the day of the vernal equinox and the moment the Sun crosses the celestial equator has been calculated for years.
[5] Mehregan is an ancient Zoroastrian and Persian festival celebrating the autumnal equinox since at least the 4th century BC.
[2][7][8] Some old Persian names in astronomy have barely survived; the names of the four Royal stars that were used by the Persians for almanacs are Aldeberan, Regulus, Antares and Fomalhaut, and are thought by scientists to equate to the modern-day star systems of Alcyone, Regulus, Albireo, and Bungula (Alpha Centauri) for almanacs.
The work contains tables for the movements of the Sun, the moon and the five planets known at the time, and is significant as it introduced Ptolemaic concepts into Islamic sciences.
Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others and learning already discovered knowledge.