Differences in moon sighting between countries and its effect on those who travel from one to another

It is not permissible to differ from the people of the city with regard to fasting and Eid

They found out during the day that Ramadan had begun, so they fasted

Is it necessary for every single Muslim to see the new moon of Ramadan?

Can Muslims living in Western countries form committees to sight the moon?

We should rely on sighting of the moon, not on calculations

Is there a certain length of time that the new moon has to be in the sky?

It is permissible to use telescopes etc., but not calculations, to sight the new moon

Sighting the moon not following astronomical calculations

The Meaning of the Verse “And the Moon, We have measured for it mansions …”