Blue Moon

Folks - I read that the full moon on 31st May is a Blue Moon (the second full moon in the calendar month). However, I heard on the radio a few days ago someone saying that the next Blue Moon was in June.

I just checked TheSky and it looks like the May date is correct. Can anyone confirm which is correct?

Cheers

Dave

I have read numerous sources before that stated 2 definitions of a Blue Moon. The first is the classical "2 Full Moons within 1 calendar month". The other is when a 4th Full Moon occurs in a quarter of a year (3 month period) - normally there are only 3.

The dates I have found for a Blue Moon this year all equal to the June one -> June 1st, and 30th.

BUT, with our timezones on the planet in operation, this can also be May 31st in some western zones, making it a Blue Moon in May for some countries!

In effect, both are correct, but the month with the longest Blue Moon in effect, is June.

Seanie.

Surely there can't be two consecutive Blue Moons?

I had another dig around TheSky and what struck me is what is the definition of a full moon? I would assume that it is a moon at its maximum phase.

According to TheSky, the Moon on 31 May is 99.80% but reaches 99.81% phase on 1st June at 00:08 - so that makes the May Blue seem out and it actually occurs in the month of June. However, I found this link

news.yahoo.com/s/space/20061229/sc_space/fullmoonnamesfor2007

that puts it as May (but is USA based)

Is it a case that the Blue Moon for us in Ireland is June but in the US they have their Blue Moon in May? ie its a case of where you live? So there could be two global Blue Moons?

Dave

Is it a case that the Blue Moon for us in Ireland is June but in the US they have their Blue Moon in May? ie its a case of where you live? So there could be two global Blue Moons?

Dave

Yep, just as I said in my post!

The wikipedia article is interesting on this too en.wikipedia.org/wiki/Blue_moon

One modern blue moon definition is for a second, extra full moon that occurs in a calendar month. The older definition of blue moon is for an extra full moon that occurs in a quarter of the year, which would normally have three full moons, but sometimes has four. Oddly, it is the third full moon in a season that has four which is counted as the "extra" full moon and named blue moon.

Because [time zone considerations are] confusing, astronomers worldwide and the calendar makers who rely on them typically choose the time zone of the Royal Greenwich Observatory, in England, or the nearly identical UTC time zone. As a practical matter, because the moon seems to the casual viewer to be full for almost three days, the use of a foreign time zone for calendar markings for full moons makes little difference.

Also skytonight.com/observing/objects/moon/33....html?page=1&c=y explains the origin of the older definition:

At last we have the "Maine rule" for Blue Moons: Seasonal Moon names are assigned near the spring equinox in accordance with the ecclesiastical rules for determining the dates of Easter and Lent. The beginnings of summer, fall, and winter are determined by the dynamical mean Sun. When a season contains four full Moons, the third is called a Blue Moon.

Interesting article Al. So, the next 'true' Blue Moon is May 2008.

The next Blue Moon according to the recent definition is June 2006 - does that make Space.com wrong (May 2006)?

Cheers

Dave