Here’s the explanation, also from DCist (which I, almost a lawyer, can’t help but pronounce “desist”):
Twice a year, as the vernal and autumnal equinoxes come upon us, nightwatchers in the D.C. area get a special treat when the full Moon’s orbit brings it up behind the Capitol building, in line with the Washington Monument, Lincoln Memorial, and Iwo Jima Memorial. Usually this occasion occurs in concert with the Harvest Moon, the name of the full Moon that occurs closest to the autumnal equinox, which happens on September 22 this year; however, this time around, the closest full Moon actually occurs after the equinox. Nevertheless, it’s September’s Moon that gives us the spectacular line up, so this year our photographers met up near the Washington Monument last night to view the Corn Moon rise behind the Capitol. Check out the gallery above for their spectacular shots. Although the official full Moon was Friday, you should still get a pretty great view tonight, — you might consider the Mall if you were looking for a romantic moon-lit walk with your partner.
Jupiter is still king of the sky these days, and we hope you took a peek last week to see it passing very near the waxing Moon. Aside from our natural satellite, it’s the brightest thing in the sky, so impress a friend by pointing it out while you’re enjoying the cooling weather on the patio this weekend. If you know someone with a decent pair of binoculars, look up at the giant planet tonight after 8:17 p.m. — you’ll see one of its moons, Ganymede, very close by as it comes out of eclipse. On Monday night, use the binoculars again to see theGreat Red Spot — a giant hurricane-like storm three times the size of Earth — at around 9 p.m. Finally, on Thursday, check it out at about 10:45 p.m. to see another moon, Io, in transit across Jupiter’s face.
One more equally-beautiful photo after the jump.