Supermoon – Check it out on Saturday March 19, 2011

by trg

Full MoonYou don’t need to have a background in orbital mechanics to appreciate the fact that on Saturday March 19, 2011 the moon will move closer to the earth than it’s ever been in the last 18 years.  At 2pm CDT, fifty minutes after the moon officially enters the Full phase, it will be 356,575 kilometers away from the earth.  Therefore the moon’s perigee, the closest point to the earth in it’s orbital cycle to the earth occurs within an hour to when the full moon actually occurs.

What this means for viewers is that the moon will appear about 14 percent larger and 30 percent brighter than most other full moons.  This is a great time to enjoy the moon!

If you are a photographer, tonight’s moon offers an excellent opportunity to try some astrophotography.  The website Beyond Megapixels has some really good tips for getting started:

  • Use a tripod for more stability.
  • The longer the lens, the better.
  • Use a remote to reduce camera shake.
  • Use a mirror lock if you have one.

What about effects on tides?
Good question.  According to Yahoo News, this event will result in a dramatic range of high and low tides:

The highest tides will not, however, coincide with the perigee moon but will actually lag by up to a few days depending on the specific coastal location. For example, in Wilmington, N.C., the highest tide (5.3 feet) will be attained at 11:21 p.m. EDT on March 20.
In New York City, high water (5.9 feet) at The Battery comes at 10:49 p.m. EDT on March 21, while at Boston Harbor, a peak tide height of 12.2 feet comes at 1:31 a.m. EDT on March 22, almost 2 1/2 after perigee.
According to the Observer’s Handbook of the Royal Astronomical Society of Canada, residents of regions along the shores of the Bay of Fundy in eastern Canada, the 10- to 20-foot (3- to 6-meter) swell in the vertical tidal range makes it obvious when the moon lies near perigee, regardless of clear skies or cloudy.
Any coastal storm at sea around this time will almost certainly aggravate coastal flooding problems.
Such an extreme tide is known as a perigean spring tide, the word spring being derived from the German springen – to “spring up,” and is not, as is often mistaken, a reference to the spring season.

So even if you’re not planning to take any photographs, tonight’s full moon may be the perfect time to start your astronomy hobby or introduce someone to astronomy.

Photo credit: Cassie_Luvitch from

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