Manhattanhenge, New York's best-known celestial show, is due for an encore performance this weekend — unless cloudy weather brings down the curtain on the sunset spectacular.
Twice a year, the sun's westward track aligns with Manhattan's central street grid to allow for sunsets that are prettily framed by skyscrapers — as if the architects had designed the city to mark the occasions. Neil deGrasse Tyson, director of the American Museum of Natural History, noted the similarity to Stonehenge's seasonal alignments more than a decade ago, and dubbed the New York phenomenon "Manhattanhenge" in tribute.
This year, the appointed days are May 28-29, and July 12-13. May 28 was a touch-and-go day for Manhattanhenge, due to rainy weather, but May 29 was a winner. Now it's time for Act II: At 8:23 p.m. ET Friday, the sun should be centered in the street just as its bottom edge kisses the horizon at sunset ("full sun on the grid"). At 8:24 p.m. Saturday, the sun should be framed by buildings when it's halfway below the horizon ("half sun on the grid").
Tyson says the best streets for viewing are 34th and 42nd streets, where the Empire State Building and the Chrysler Building add to "especially striking vistas." Other clear cross streets include 14th, 23rd, 57th and several streets adjacent to them. In his guide to Manhattanhenge, Tyson recommends staking out a viewing area as far east in Manhattan as possible, at least a half-hour before sunset.
Future anthropologists might well take note of the fact that the Manhattanhenge rites roughly coincide with Memorial Day and baseball's All-Star Game. "So they would conclude that America was about war and baseball," Tyson says in a brand-new video about the phenomenon. Do you think he's serious?
Over the past few years, growing crowds of New Yorkers have flocked to the streets to witness the rites of summer. The crowds are getting so big that tweeters are starting to refer to "Peoplehenge" rather than Manhattanhenge.
In May, Tyson told NBC News that he thought the New York Police Department should be closing off streets to control traffic, and some of the tweets from Manhattanhenge's early birds suggest that Tyson's advice is being followed. On Thursday night, for example, 79th Street was closed off for a pre-Manhattanhenge viewing party at the museum.
The views were spectacular on Thursday — and we can only hope they'll be as good on Friday and Saturday, even though the weather forecast calls for gray skies. "Keeping my fingers crossed," Andrew Dallos, a producer for MSNBC's "Rachel Maddow Show" who is also a Manhattanhenge aficionado, said in a tweet.
How will this weekend turn out? You can keep track by following the #Manhattanhenge hashtag on Twitter, or doing a search on Flickr, YouTube and Vimeo. And whether it's in Manhattan or Montreal, share that perfect sunset with the rest of us.
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Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.