slâm dinindeki pek çok ibadet vakti, astronomik olayların teşekkül edişine göre belirlenir. İbadetlerin yerine getirilmesi kadar, kerahet vakitleri gibi kısıtlamalar da yine gök olaylarının gerçekleşme durumuna göre belirlenmiştir. Örnek vermek gerekirse, (i) oruca başlama (ya da sabahın başlangıç) vakti olan imsak olayı, (ii) hicrî takvimdeki aybaşlarını belirleyen Rü’yet-i hilâl olayı, (iii) en temel ibadet olan namazın giriş – çıkış vakitlerini belirleyen Güneş’in ufka göre konumu, (iv) Hac’da vakfe (9 Zilhicce, arife) günü gösterilebilir. Hatta bazı ibadetlerin yapılmasının mekruh olduğu (Bayram günü oruçlu olmak, Güneş doğup batarken namaz kılmak vs. gibi) vakitler bile, tamamen astronomik gök olaylarıyla tespit edilmektedir. Bu bağlamda, İslâm dini açısından astronomi biliminin önemi göz ardı edilemez. Bu çalışmada, tan ve fecr vakitlerinin duyarlı bir şekilde, modern astronomik yöntemlere dayalı olarak, gözlemsel yolla nasıl tespit edildiği anlatılmaktadır.

The exact time of many worship in Islam is depend on the appearance of some certain astronomical events. Some restricted times for worship, as well as makruh hours, are determined by the related celestial events. For instance; (i) start timThe exact time of many worship in Islam is depend on the appearance of some certain astronomical events. Some restricted times for worship, as well as makruh hours, are determined by the related celestial events. For instance; (i) start time of abstinence, i.e., beginning of fajr, (ii) sighting of crescent (Ru’yet-i Hilâl) moon, which adjusts the beginning of hijri months, (iii) the horizontal position of the Sun in the celestial sphere, which determines the preliminary and termination hours of the salah, the main worship, (iv) standing in the eve day in Arafat during Hajj, i.e., 9 Dhu'l-Hijja. Moreover, some prohibited (makruh) time intervals of performing any worship such as fasting in the Eid al Fitr and Eid al Adha, performing salah during sunset and sunrise, etc., are all defi ned by appearance of certain astronomical events. In this context, the implications of astronomical observations are very essential on Islamic opinions. In the present study, precise time determinations of dawn and fajr events performed on the basis of modern astronomical methods are given and interpreted. e of abstinence, i.e., beginning of fajr, (ii) sighting of crescent (Ru’yet-i Hilâl) moon, which adjusts the beginning of hijri months, (iii) the horizontal position of the Sun in the celestial sphere, which determines the preliminary and termination hours of the salah, the main worship, (iv) standing in the eve day in Arafat during Hajj, i.e., 9 Dhu'l-Hijja. Moreover, some prohibited (makruh)