Be Prepared For Manhattanhenge! May 29-20
May 29, 2012

Be Prepared For Manhattanhenge! May 29-30

Lee Rannals for

On Tuesday evening, residences and onlookers in Manhattan will be treated to a sunset spectacle known as Manhattanhenge.

During the event, a half sun will align itself perfectly with the city's 201-year-old grid at 8:17 p.m. as it sets right in line with the streets of Manhattan in New York.

The steel construction echoes a similar effect created by Stonehenge, as the ancient arrangement matches the direction of the midsummer sunrise and midwinter sunset.

Because Manhattan is laid out in a grid, it provides two days a year where the sunset is exactly in line with all the cross streets on the island.

The sun will come down to Manhattan streets at a diagonal angle, until half of it perfectly sets in line with the streets.

Those who will miss Tuesday's event will get a second chance on Wednesday, except on that day it will be a full sun, as opposed to Tuesday's half sun.

For the best effect, one should position themselves as far east in Manhattan as possible, and look west across the avenues toward New Jersey, according to Hayden Planetarium.

Tomorrow's full sun on the grid will take place at 8:16 p.m.  If both events are missed, New Yorkers can get a second chance in July.

On Thursday, July 12, Manhattan residents will be treated to a half sun on the grid at 8:25 p.m., then a full sun display on July 11 at 8:24 p.m.

The Sun actually rises due east and sets due west only twice per year: on the first day of spring and the first day of autumn.  Every other day, the Sun rises and sets other places on the horizon.

If Manhattan's grid was perfectly aligned with the geographic north-south line, then the days of Manhattanhenge would coincide with the equinoxes.

Manhattan's street grid is rotated 30 degrees east from geographic north, shifting the days of alignment other places into the calendar.

Any city that has perfectly aligned streets are able to have days that coincide with a sunrise or sunset, but most cities around the world do not offer the same variables that New York does.

The Sun always rises at an angle up, and to the right, and sets at an angle down and to the right.  According to the Hayden Planetarium, using this method of the sun rising and setting is how you can spot a fake sunrise, or sunset, in a movie.