Once in a Blue Moon

You learn something new every day, and today it was the origin of the saying ‘Once in a blue moon’.
A ‘Blue Moon’ is a second full moon in one month - which is really unusual, the next one is a decade or so away - hence the saying.
This Blue Moon was especially interesting as it is also a ‘Harvest Moon’ which is where the moon is closest to earth and appears quite large in the sky., sadly it was well risen by the time the clouds cleared so we could see it.