( CNN ) -- If the moon looks a little bit bigger and brighter this weekend , there 's a reason for that . It is . Saturday 's full moon will be a super `` perigee moon '' -- the biggest in almost 20 years . This celestial event is far rarer than the famed blue moon , which happens once about every two-and-a-half years . `` The last full moon so big and close to Earth occurred in March of 1993 , '' said Geoff Chester with the U.S . Naval Observatory in Washington . `` I 'd say it 's worth a look . '' Full moons look different because of the elliptical shape of the moon 's orbit . When it 's at perigee , the moon is about 31,000 miles ( 50,000 km ) closer to Earth than when it 's at the farthest point of its orbit , also known as apogee . `` Nearby perigee moons are about 14 % bigger and 30 % brighter than lesser moons that occur on the apogee side of the moon 's orbit , '' the NASA website says . This full moon will rise in the east at sunset and should look especially big at that time because of what 's known as the `` moon illusion . '' `` 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 , '' according to NASA . iReport : Share your photos . Even though it may look close enough to touch , Saturday 's full moon will still be at a healthy distance -- some 211,600 miles ( 356,577 km ) away . As rare as it is , it may be worth a look . Miss it and you 'll have to wait until 2029 to see it again .
The last full moon so big and close to Earth was in March of 2007 . Friday 's full moon will be the biggest in almost 20 years . Saturday 's full moon will still be 211,600 miles away . This full moon will appear about 14 % bigger and 30 % brighter .