The prompt to me means that a blue moon is a beautiful occurrence that happens when two full moons fall in the same month with the second often being called the blue moon.

They're cool and I really liked this prompt.

I tried to include a moon but it got hidden in the midst of the render and everything.

I'm not expecting this cover to place because it's not good but I haven't entered a contest on a while so I figured why not enter yours :)