Reducing Sky Glow

Stargazing is awesome! But sometimes, the night sky is not visible due to light pollution. In cities like Nashville, a common type of light pollution is “sky glow”.
Sky glow is the brightening of the entire night sky, especially in populated areas. The light pollution around Nashville inhibits our view of zodiacal light, airglow, and many of the Messier objects.

Bortle Dark-Sky Scale by Skyglowproject

How can we reduce sky glow? One method for cities to reduce skyglow is to reduce uplighting and excess / wasteful light through shielding or cutoff lights. For other tips, check out this blog by Mara Bermudez.

Shielded Lights

Light fixtures prevent light from immediately scattering in the atmosphere. Many fixtures also aim the light towards the ground, reducing glare and providing better ground visibility. Light shielding also reduces unwanted lighting on other people’s property, called light trespass.

Cutoff Lights

The Main Types of Cutoff Lights. by The Nguyen Manh, slide 26.

Cutoff lights focus light towards the ground similarly to shielding fixtures. The amount of cutoff determines how much light gets distributed at or above the horizontal. Cutoff lights have many benefits, including focused light for better surface visibility, and less uplighting, which is wasteful and the excess light scatters in the atmosphere.

In Nashville

Broadway night life in downtown Nashville. by John Russell/Vanderbilt University

Many of the street lights at Vanderbilt University are non-cutoff, as shown in this picture on the Vanderbilt admissions page of downtown Nashville. This type of light pollution contributes to the skyglow around Nashville.