Blue Moon??

There seems to be various defintions of what is a blue moon. According to wiki, there seems to be three main concepts:

An atmospheric effect for a time after forest fires or volcanic eruptions

Two full moons in a month which apparently was a misintreptation of data

Or the third full moon in a season (determined by the equinox) where are there are four full moons.

Full article is at: en.wikipedia.org/wiki/Blue_moon#Visibly_blue_moon

Anyone have any particular views on this?

I've always believed that it meant two full moons in a calendar month.

I'm not sure how volcanoes or forest fires can turn the moon blue, I would have thought that the extra dust in the atmosphere would dull it to a dark grey colour.

I've never heard of the last explanation, if that were the case there would be more blue moons, wouldn't there?

I heard that "interpretation" was a mistake made by Sky and Telescope which they later retracted...

lunartic wrote:

I've always believed that it meant two full moons in a calendar month.

I've always thought that it was two full moons in one calendar month.

I found this but doesn't help much - the National Maritime Museum in the UK. In fact they appear to go for the blue hue caused by volcanic eruption or large forest fire.

www.nmm.ac.uk/explore/astronomy-and-time.../once-in-a-blue-moon

The Sky and Telescope origins sound very credible but I am a bit suspicious of the origin being rooted in the farming comunity of Maine in the USA in 1930s. I find it strange that the phrase "once in a blue moon" would be so pervasive this side of the Atlantic if that were the case.

www.skyandtelescope.com/observing/objects/moon/3304131.html

It is interesting to note though - that four full moons in a single season or 13 full moons in a 12 month period still requires the presence of two full moons in one calendar month somewhere. Then the choice boils down to which one is special - in my mind the only real candidates are the first or the second of a pair in one calendar month and I'd have to swing for the second as you haven't really got an exception until that arrives.

An interesting one - I wonder what field studies this sort of stuff.

Mark

As I recal,
a Blue Moon was described by viewers of a full Moon
after an eruption some time back (can't remember which or when)

S&T did publish something which it was picked up in
but I think they now take some kind of credit for
it (rightly or wrongly) having come to mean
two full Moons in a calendar month.

eclipsedan wrote:

I heard that "interpretation" was a mistake made by Sky and Telescope which they later retracted...

lunartic wrote:

I've always believed that it meant two full moons in a calendar month.

Yea, read that also, a mistake by S&T that stuck.