Most of the Muslim festivals including the start and end of Ramzan and the festival of Eid are all based on actual sighting of the crescent of the new moon.
This crescent if less than 12 hrs old cannot be seen with naked eyes. In fact it s only visible with naked eye once it is 20-30 hours old.
That’s the reason why many of the Muslim communities appoint a “Hilal”, which is a Crescent sighting community especially for this purpose and to calculate the dates of Islamic calendar.
The factors that majorly affect the sighting of a new moon are:Distance at that moment of moon from Earth:
- The height of the observer above sea level.
- Clarity of atmosphere.
- Wind directions.
- The eye-sight quality of the observer.