1)  Misdirected Lighting. Streetlights, security lights and billboard lights are often the main culprits. Although these lights do light up their intended targets, they also spill out, up, down and around them too! Light pollution in this case is caused by the light being directed above and beyond the target and up into the night sky.

2)  Improper Lighting Cutoff. Some lighting fixtures are actually designed such that light escapes directly upward and into the night sky. A simple lighting cutoff cap placed over the offending light will not only block the light that would normally head upward into space, but also reflect some of that light back to the intended target, thus minimizing the need for high power lighting!

3)  Excessively Powerful (high wattage) Lighting. Some lighting is just too excessive. When you pass by a bright streetlight or security light do you say, "Is this high brightness really necessary?". Most individuals who install such fixtures are not thinking about what these lights can do to the night sky. Nevertheless, they are still wasting money on two fronts: spilling a percentage of the lighting into the night sky AND using too much electricity to power the excessively high power lighting!

4)  Unnecessary Lighting. Some lighting isn't even necessary! The next time you turn on that light at night, ask yourself, "Is this light really doing anything constructive? Is this light really worth the extra money in electricity I am paying? Do I really need these lights to be on all night (and in some cases all day), or should daylight and motion sensors be used?"