What should the size of my moons be?

(Not entirely sure if this is the right place to ask this but hopefully I'm right!)

I'm writing a novel and the planet this novel takes place on has two, twin moons of approximately the same size. The idea here is that the seasons are split up by the coming and passings of the moons - essentially, they are determined by where each moon is in the night sky relative to the sun. As a result, the cycle of each moon is approximately the length of a full year - which in itself is ~350 days long.

In addition, the days are pretty much the same length as those on Earth. I didn't want to change too much in case I'd be altering far more than I know. The seasons I'm referring to here just happen to coincide with the positions of the moon - hence why the populace believes that the positions of the two moons are what cause the change in seasons.

In order to have such long moon cycles, and two moons at that, how would I go about doing the calculations for their masses/sizes/mineral makeup? At least how far away should the moons hypothetically be in order to not make the planet a uninhabitable? And how might this affect gravity on the planet - IE is this even possible?

posted over 5 years ago

doplin‭

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