DarkSky International — Outdoor Lighting, Sky Glow & Light Trespass

This March 2026 DarkSky International white paper examines outdoor light emitted near the horizon, particularly between 80 and 90 degrees from downward vertical. It concludes that this high-angle light provides little useful illumination in many roadway, pedestrian and industrial applications while contributing to sky glow, glare and light trespass.

Horse Creek is currently a dark, open rural landscape where poorly controlled industrial lighting could be visible well beyond the project property. This study provides a technical basis for asking Black Hills Energy to provide a detailed lighting plan and use targeted, shielded lighting with strict limits on unnecessary near-horizontal light.

Independent Technical White Paper