The CityHenge visualization was developed originally as an idea to display the use of VECKNIK with OpenStreetMap data. The map shows the sunset angle across New York City for every day of the year, allowing you to find Manhattanhenge events year round.
There is some more info about the project on this blog post
The original presentation was given at the 2013 SOTMUS Conference. Watch it here.
We hope you enjoy it.