Photo by keithmuth.

Tomorrow, beginning at 5:04 a.m. eastern standard time, the tilt of the Earth’s axis will be situation neither away from nor towards the Sun, marking the autumn equinox and the beginning of fall. And while that’s pretty neat in and of itself, it’s the yearly D.C. Henge event that really has us excited. Our resident astronomy expert, Heather Goss, concisely explained the “Henge” phenomenon last year:

The name was coined by popular astrophysicist (I just like typing that) Neil deGrasse Tyson…who wondered aloud if future archaeologists would dig up Manhattan and believe it had astronomical significance, with its architecture lined up to greet the sun, as Stonehenge does during summer and winter solstice.

D.C. and New York City experience this phenomena on different days, since Manhattan’s perpendicular grid of streets is tiled about 30 degrees off-axis, while ours lines up directly north-south and east-west. As deGrasse Tyson notes, the sun sets directly west twice a year, on the equinoxes. […] Since the sun moves only a smidge in the sky each day, we’ll actually be able to see it setting down our alphabet streets most of the week [and] between, you know, the awe-inspiring lobbies of a couple of ten-story law firms.

And as you can see from the above photograph, tomorrow could a pretty good day to wake up early, bust out that camera and grab some photographs. As we recommended last year, the Photographer’s Ephemeris is a street shutterbug’s best friend when it comes to figuring out the optimal place to document D.C. Henge — that is, if you can manage to find the sun through the gloomy skies. (And, of course, our Flickr pool isn’t a bad place to drop your best shots.)