Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions. Wa alaikum assalam wa rahmatullahi wa barakatuh. As to what follows: In response to your question, we say: Observatoriesare a type of moon sighting but they rely on the modern equipment. Thus there is no problem in using observatories in sighting the crescent. Several bodies including the Council for Senior Scholars and other Fiqh academies have given fatwas to this effect. However, the issue of astronomical calculations is a different matter. Some scholars have mentioned that there is a consensus of opinion among the scholars that astronomical calculations should not be considered. Some Malikite jurists have said, “If astronomical calculations are relied upon to determine the start of Ramadan, people should not be compelled to follow the information or announcement that is based on them to state that the month of Ramadan has started. This isthe opinion of the majority of contemporary scholars.