So here you have two definitions of a blue moon but the one for a calendar blue moon does not describe the true meaning of a blue moon. Here's why:
Earth's Moon is enchanting; bewitching. The face of the "man"--that some cultures see etched on its brilliant surface--is really composed of the dark areas of the lunar maria (Latin for "seas"), and the lighter highlands of the Moon's surface. Some cultures tell of other examples of strange images seen on the Moon's lovely disk, such as the "Moon Rabbit".
The team of astronomers used the same HST technique to observe the little moon as they did for discovering the small moons of Pluto in 2006, 2011, and 2012. Several earlier hunts around Makemake had not succeeded in spotting it. "Our preliminary estimates show that the moon's orbit seems to be edge on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake," commented Dr. Alex Parker in an April 28, 2016 Hubble Press Release. Dr. Parker, who led the image analysis for the observations, is of the Southwest Research Institute in Boulder, Colorado.