The Teton Count lighting ordinance requires first that

 “Exterior lighting brighter than a 60 watt incandescent light shall be shielded so that no light is projected above the horizontal, …”

 

This is what is usually known as fully shielded.  Another common designation is full-cutoff, which also limits light that may go into people’s eyes,  Some manufacturers call these “Dark Sky Friendly” or “Neighbor Friendly”.  The picture shows what it all means.

 

 

 

 

 

 

 

 

 

 

 “fully shielded” lights.  This means that no light shines upward from the fixture.   If your eyes are at the level of the fixture, you should not be able to see light coming directly from

Cover:  The cover  shows a color  map of skyglow in the Valley  from satellite measurements: See P. Cinzano, F. Falchi , and C.D. Eldredge,

http://www.lightpollution.it/dmsp/artbri.html

 

View: Google Earth