You always read about how comets and full moons are bad omens. Like a nation is defeated in battle on the same day Comet Acme comes by. Thus it is a bad omen.
But what about the guys who won? Wouldn’t they consider it a good omen?
Are there instances of this in history?
I just had to read through a pile of 16th C German prints reporting miracles and portents. If something was taken as an omen, they never seemed sure what it was supposed to mean, but they knew it must mean something. A comet could be a warning of God’s wrath, or a sign of his blessing-- it was usually interpreted for some political reason (he probably believed he was correct, though) by the printmaker. So if that time and place is any indication, omens generally are vague signs that can be interpreted any number of ways, depending on who makes the best guess. Subsequent events would prove what it had meant to communicate.