Once in a Blue Moon
August 17, 2015
Captured in my backyard with my Canon SLR and 1500 mm lens. The origin of the term "blue moon" is unclear as certain rare atmospheric conditions can actually give the moon a blue tinge. Today, the term has less to do with the colour of the moon, as you can tell by the unedited photo, and more to do with the timing of the moon.
It takes 29.53 days for the Moon to complete one phase cycle or lunation. (www.moonconnection.com/moon_phases.phtml). It takes the Earth 365.24 days to orbit the Sun. So each calendar year has about 3 full moons per season, and about 12 full moons in total (365.24/29.53 = 12.37). Every two to three years there are 13 full moons in one calendar year, giving one season four full moons. The "blue moon" refers to the third full moon in a season of four full moons. Over the years this has been misinterpreted to be a calendar month of two full moons, though this isn't entirely incorrect. (http://www.space.com/17291-blue-moon-night-sky-friday.html)
An asteroid or comet headed for Earth is the only large-scale natural disaster we can prevent. Working together to fund our Shoemaker NEO Grants for astronomers, we can help save the world.