If any jurist whose opinions are followed – Marja’a al-Taqlid – has announced the beginning of the month of Ramadan, can all Shi’ahs in these regions start the fast?

There are two opinions on this matter:

a. If the latitude where you live is approximately the same as the latitude where the
Marja’a al-Taqleed lives, you may. If there is a substantial difference you may not.

b. When the moon is cited in one city, it is also considered to have been sighted in every other city which shares some part of that night with it. This means, all cities where either the commencement and/or end of night coincide, to any degree with the city in which the moon was sighted. In other words, almost all the cities on one half of the globe. I strongly support this second opinion.