NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 70 7. Glossary8 8 Some definitions in this glossary are from ANSI/IES RP-16-17, “Nomenclature and Definitions for Illuminating Engineering” (ANSI/IES 2020); others are from “Joint IDA-IES Model Lighting Ordinance with User’s Guide” (IDA-IES 2011). adaptive controls: any electronic or mechanical device attached to a light intended to dynamically control the duration, intensity, spectrum, or area illuminated by the lighting. aircraft detection lighting system (ADLS): radaractivated lighting technology designed to reduce the impact of nighttime lights by deploying a radar-based system around a facility, turning lights on only when low-flying aircraft are detected nearby. artificial light at night (ALAN): light that arises from nonnatural sources (i.e., light that does not occur in the natural environment without some action by humans). There are many possible sources of artificial light, but the most common sources involve passing electrical current through various materials. Lighting used specifically to provide illumination during the hours of twilight or darkness. astronomical light pollution: light pollution that obscures the view of the night sky. See light pollution and ecological light pollution. backlight: light emitted in the quarter sphere below horizontal and in the opposite direction of the intended orientation of the luminaire. best management practice (BMP): a practice or combination of practices that are determined to provide the most effective, environmentally sound, and economically feasible means of managing an activity and reducing its effects. bioluminescence: a type of natural light produced by some form of chemical reaction within a living organism. Bioluminescence occurs in marine vertebrates and invertebrates, some fungi, bacteria and other microorganisms, and certain terrestrial invertebrates (e.g., fireflies). BUG rating system: BUG is an acronym for backlight, uplight, and glare. The “Luminaire Classification System for Outdoor Luminaires,” IES TM-15-20, BUG rating system (IES 2020) is a tool used to quantitatively evaluate the light output of an outdoor luminaire and, in particular, the light escaping in unwanted directions. The system is based on a sphere around a hypothetical polemounted light source in the center of the sphere. The sphere is divided into three sections: backlight, uplight, and glare (forward light). The three sections are further divided into zones in which the lumen distribution is rated to determine the light pollution impact of the luminaire. The BUG rating system replaces the earlier “cutoff” system. candela: a unit of luminous intensity in the International System of Units (SI); that is, luminous power per unit solid angle emitted by a point light source in a particular direction. A common wax candle emits light with a luminous intensity of roughly one candela. See lumen. circadian rhythm: a roughly 24-hour cycle in the physiological processes of plants, animals, fungi, and other living things. Circadian rhythms are endogenously generated but can be modulated by external cues such as sunlight and temperature. color: the property of reflecting or emitting light of a particular intensity and wavelength (or mixture of wavelengths) to which the eye is sensitive. color rendering index (CRI): a measure of a light source’s accuracy in rendering different colors properly. To determine CRI, a given light source is compared to a standard reference light source with the same correlated color temperature (CCT). CRI uses a scale from 0 to 100 percent. The higher the CRI, the better its color rendering ability. See correlated color temperature (CCT).
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