Many New Yorkers seek to escape the city on Memorial Day weekend, but if you happen to be there today or tomorrow, you'll be rewarded with a special treat around 8:12 pm. That's when a special astronomical event called "Manhattanhenge" takes place.

Manhattanhenge was named by astrophysicist Neil deGrasse Tyson as a nod to Britain's Stonehenge, where the sun aligns perfectly in the center of the northeastern entrance during the summer and winter solstices. On Manhattanhenge day, the setting sun aligns perfectly with Manhattan's numbered streets, so that you can look across the island and see the sunset perfectly framed between buildings.

If Manhattan's east- and west-bound numbered streets truly did run east and west, Tyson explains, then Manhattanhenge would fall on the spring and autumn equinoxes every year (approximately March 20 and September 23). But because Manhattan's "East" and "West" streets are tilted slightly off true east and west, the day changes slightly each year.

On the first day of Manhattanhenge, a few minutes before sunset, the sun appears as a half-orb peeking over the horizon and perfectly centered on the East-West streets. On the following evening at the same time, the sun will again align perfectly on the horizon, this time as a full orb. 

What are the best places to view--and photograph--Manhattanhenge? Tyson advises getting as far east as you can on the island because this will give you the most buildings to create the best frame. He suggests the unobstructed "cross streets" including 14th, 23rd, 34th, 42nd or 57th Streets. "The Empire State building and the Chrysler building render 34th street and 42nd streets especially striking vistas," he notes.

For best results, arrive at least half an hour early (there will be other people there for the same purpose). Look down the street and make sure you can see across the Hudson to New Jersey--if you can't, the effect won't work. Oh, and be careful you don't get flattened in busy Manhattan traffic.

If you miss tonight's half-orb, or would rather see a full orb instead, you can come back tomorrow (Monday) night for that view. And if you miss both, Manhattanhenge will come around again on July 11 and 12, with the full orb on the first day and the half-orb on the second.