This TM describes the causes, characteristics, and potential impacts of human-based sky glow, and provides the current state of the science for conducting estimations to facilitate its quantification and control. Virtually all lighting applications with exposure to the exterior environment fall within this purview, including street and area lighting, sports lighting, signage and advertisement lighting, industrial lighting, light escaping the interior of commercial and
residential buildings via windows, and landscape lighting. Mobile sources, i.e., vehicular lighting, also contribute to sky glow and are included in the discussion, even though they are traditionally outside of IES scope.

This document only provides an introduction to light’s potential downstream consequences, e.g., impacts to human health or wildlife, and provides the basis of a methodology for one or more new metrics. The process often involves the application of a dedicated action  function specific to the effect in question and therefore requires special domain expertise that is beyond the ability of this document to provide.* However, the methodology will enable estimates of underlying inputs such as the spectrum, intensity, duration, and timing of the light that are necessary to conduct such expert assessment.

Consequently, this TM focuses on the causes and characterization of light that may be introduced to the night sky from the use of electric lighting, and available means of influencing it. A proposed method for its numeric quantification is also included, for detailing individual contributions to light in the sky, application by application. More work is needed to fill in the details of this method and create the ultimate recommended practice, but the methodology establishes a practical framework. In the meantime, Section 5.2 provides a few brief references
to models and tools that are currently available for estimating sky glow, while Section 7 provides general recommendations for reducing sky glow that should prove useful throughout the lighting community.