Blue Moon, Eclipsed Moon, Rises at Sunset

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As the sun sets on January 31, the full moon will rise eclipsed -- but the eclipse will be invisible. It will also be a blue moon -- but the colour of the moon will be perfectly normal. And February will be less romantic than in years -- except in Australia.

Sunrise and moonset

Sunset on January 31 will be at 19:52; moonrise will be at 19:48, giving nearly perfect symmetry for those who throng Signal Hill to watch such events.

Invisible eclipses

When sunlight is only partially blocked by the earth as seen from the moon, we get a penumbral eclipse -- which means that the moon is just a bit dimmer than usual and nobody notices but astronomers. You aren't likely to be able to tell, but this virtually invisible eclipse ends at 20:30 SAST.

Blue Moons

Since the 1970's and 80's, it has become customary to refer to a second full moon in a month as a "blue moon". This year January has full moons on both the 2nd and the 31st. Blue moons occur about 7 times every 19 years, so they aren't really all that rare. There was a blue moon in 1996, and there'll be another one in 2001. But this year South Africa has two blue moons, which hasn't happened since 1961 and won't happen again until 2018. There are about 4 double blue moons each century.

February Without Romance

A double blue moon like the ones this January and April (January and March in North America, because of the difference in time zones), always means that February has no full moon at all. But in Australia the time zone difference means that our full moon on January 31 (18:06 SAST) is a Feb. 1 full moon at 2:06 by Sydney time. The last time there was no full moon in February anywhere in the world was 1866. Enough to make St. Valentine himself feel blue.

Contact: David Laney

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