According to The Atlantic , Manhattanhenge is:

… the twice-a-year phenomenon when the sun sets exactly along the cross streets of New York City’s prodigious grid….

From the Roosevelt Island Twitterverse:

Hugh is right. Here’s Manhattanhenge seen from a Roosevelt Island Manhattan Park balcony tonight

More information on Manhattanhenge from Neil deGrasse Tyson of the American Museum Of Natural History

and these previous posts. UPDATE 10:40 PM – Diana Desrocher shares another awesome, though cloudy, Manhattanhenge view

Image From Diane Desrocher from Manhattan Park tonight. UPDATE 6/2 -Isis Barquero shares more Manhattanhenge photos seen from Roosevelt Island. These were taken June 1 from Southpoint Park.

Images From Isis Barquero