I think this is possibly my favourite ever headline in the Independent -
"How to see the rare lunar event tonight"
The rare lunar event tonight is a blue moon, which is indeed a rare event, as we all know from the expression "once in a blue moon". It is, however, simply a full moon. It's called a blue moon if there has been more than one full moon in the same calendar month.
By some distance, then, the easiest way of seeing a blue moon is to look at the moon.