Muslims have always had a special interest in astronomy. The moon and the sun are of vital importance in the daily life of everyMuslim. By the moon, Muslims determine the beginning and the end of the months in their lunar calendar. By the sun the Muslimscalculate the times for prayer and fasting (sawm). It is also by means of astronomy that Muslims can determine the precise directionof the Qiblah, to face the Ka'bah in Makkah, during prayer. The most precise solar calendar, superior to the Julian, is the Jilali, devised under the supervision of Umar Khayyam