In most cases, dark sky compliance refers to three variables.
- FIXTURE ITSELF: The fixture itself must not release more than 8% of its lighting upward. This means that the fixture whole on can not shoot more than 8% of its light upward to the sky.
- MOUNTING: The way the the fixture is mounted is crucial. The fixture itself must be mounted so that it faces downward directly with no tilt or rotation. The Fixture should mounted perpendicularly to the service at a 90 degree angle.
- NO TILT OPTION: The fixture must be mounted in such a way that it has no option to tilt. This means the mounting must be a flem or something similar. Slip fitters will not truly satisfy most dark sky compliance ordinances because it has the option or ability to be tilted or adjusted.
As with all ordinances, these standards will vary by state or province and all ordinances should checked with locally before installing lights.