Q. Does the recent “Blue Moon” last sighted on Wednesday August 30, in Toronto, have any significance in our lives?
Is there any special blessings to be recited upon seeing this phenomenon?
A. “Once in a blue moon,” is a common expression that has been used for a long time, and which means ‘not very often,’ or ‘very rarely.’ It often refers to an extra full moon; however, it has been used to describe the way the moon actually looked, when for different reasons it had turned a bluish color.
The expression “blue moon” has been around for a very long time, and it almost always refers to a full moon of a very special kind, but sometimes it is a description of the moon, which for different reasons turns blue. When the famous volcano Krakatoa exploded and lots of dust was sent into the atmosphere, it made for some very unusual skies, including blue moons! ( https://www.loc.gov/really)
On question 1417 we were asked: “The Mishnah Berurah (beginning of siman 229) says that one should not publicize the sighting of a rainbow because it is like Lashon Horah. Should one also refrain from publicizing the event of a lunar eclipse which, according to popular translation of the gemora (Sukka 29a), is referred to as a bad sign for Jews?
To what we answered: “Although Mishna Berura (229: 1) quotes from Chaye Adam the term motzei dibo is does not refer or imply the common Lashon Hora’ meaning, but rather conveying something that may be harmful or proscribed to another, as gazing at the rainbow may be. (Taanis 16, Remah, Mishna Berura ibid 5).
However, in regards to announcing or publicizing a lunar eclipse, Horav Shlomo Miller's Shlit'a opinion is that it is different than a rainbow.
A supermoon occurs when the moon reaches its closest point to Earth in its orbit, and a blue moon describes the second full moon within a calendar month.”
Rabbi A. Bartfeld as revised by, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit'a