I do not understand how an Astrologian does its Magic.

[YianKutku]

That said, it's clear that the Astrologians are not infallible. Like most, they thought that Dalamud was a true moon and plotted their astrology accordingly - up to the point when it was called down and Bahamut broke free. Even afterwards, though, they continue to perform their astrology assigning importance to the empty place Dalamud used to be.

I've always been curious about this. From the example of Dalamud and its current absence, it's clear that what the Astrologians believe to be true may not actually be the case... but they still manage to construct an entire discipline, complete with tangible effects and outcomes, out of this belief. When questioned how, I recall the in-game answer being "we have no idea, but it all works out anyway".

They base their calculations on mistaken premises, but even after the truth is revealed, those calculations still work. Something is going on here.