Blue moon? Friday's celestial event comes with a catch
BY: mwilliams 07:16, July 31, 2015
This is an astronomy story that comes up only once in a blue moon, like on Friday. Maybe.
When the full moon appears at 6:43 a.m. EDT Friday, it will become the second full moon of July. Geoff Chester of the U.S. Naval Observatory said the traditional definition of a blue moon is two full moons in a month.
It happens about every 2½ years and has nothing to do with color.
But there's a catch that may disqualify this as a blue moon.
Chester said an older definition from a Maine almanac calls a blue moon the fourth full moon in an astronomical season. This is only the second full moon of summer, so by that definition no blue moon.