Super Full Moon   
       
   March 16, 2011: Mark your calendar. On March 19th, a full Moon of rare size   
   and beauty will rise in the east at sunset. It's a super "perigee moon"--the   
   biggest in almost 20 years.   
       
   "The last full Moon so big and close to Earth occurred in March of 1983," says   
   Geoff Chester of the US Naval Observatory in Washington DC. "I'd say it's   
   worth a look."   
       
   Full Moons vary in size because of the oval shape of the Moon's orbit. It is   
   an ellipse with one side (perigee) about 50,000 km closer to Earth than the   
   other (apogee): diagram. Nearby perigee moons are about 14% bigger and 30%   
   brighter than lesser moons that occur on the apogee side of the Moon's orbit.   
   [...]   
   Above: Perigee moons are as much as 14% wider and 30% brighter than lesser   
   full Moons. [video] "The full Moon of March 19th occurs less than one hour   
   away from perigee--a near-perfect coincidence1 that happens only 18 years or   
   so," adds Chester.   
       
   A perigee full Moon brings with it extra-high "perigean tides," but this is   
   nothing to worry about, according to NOAA. In most places, lunar gravity at   
   perigee pulls tide waters only a few centimeters (an inch or so) higher than   
   usual. Local geography can amplify the effect to about 15 centimeters (six   
   inches)--not exactly a great flood.   
   [...]   
   The Moon looks extra-big when it is beaming through foreground objects--a.k.a.   
   "the Moon illusion." Indeed, contrary to some reports circulating the   
   Internet, perigee Moons do not trigger natural disasters. The "super moon" of   
   March 1983, for instance, passed without incident. And an almost-super Moon in   
   Dec. 2008 also proved harmless.   
       
   Okay, the Moon is 14% bigger than usual, but can you really tell the   
   difference? It's tricky. There are no rulers floating in the sky to measure   
   lunar diameters. Hanging high overhead with no reference points to provide a   
   sense of scale, one full Moon can seem much like any other.   
       
   The best time to look is when the Moon is near the horizon. That is when   
   illusion mixes with reality to produce a truly stunning view. For reasons not   
   fully understood by astronomers or psychologists, low-hanging Moons look   
   unnaturally large when they beam through trees, buildings and other foreground   
   objects. On March 19th, why not let the "Moon illusion" amplify a full Moon   
   that's extra-big to begin with? The swollen orb rising in the east at sunset   
   may seem so nearby, you can almost reach out and touch it.   
       
   Don't bother. Even a super perigee Moon is still 356,577 km away. That is, it   
   turns out, a distance of rare beauty.   
       
       
   Author: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   1Footnote: Less-perfect perigee moons occur more often. In 2008, for instance,   
   there was a full Moon four hours from perigee. Many observers thought that one   
   looked great, so the one-hour perigee moon of 2011 should be a real crowd   
   pleaser.   
       
   Lunar Perigee and Apogee Calculator   
       
   What are the "Perigean Spring Tides"? Do they cause coastal flooding? -- an   
   explanation from NOAA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.59   
    * Origin: NCS BBS (1:3828/7)