NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 59 Notes: In some cases, mounting lights at the top of a structure is more expensive than installing lights on the ground and is less convenient from a maintenance standpoint. If installed on the ground, shield the luminaires to minimize light going into the sky. 5.4.12 Avoid the Use of Swivel-Mounted Floodlights Because of the potential for improper aiming, avoid the use of swivel-mounted floodlights. Avoiding swivel-mounted floodlights reduces the potential for skyglow, light trespass, and glare. Notes: Use of any lighting product that includes mounting equipment that allows the user to change the orientation of the lighting is not considered best practice, because of the potential to improperly aim the light. 5.4.13 Avoid Uplighting Where Possible Uplighting is not recommended, except where the luminaire is shielded from the night sky by a roof overhang or similar structure; where the luminaire does not cause light to extend beyond the structural shield; or where available luminaire mounting locations are limited and specific lighting tasks require uplighting for safety reasons. Notes: Uplighting is frequently used for aesthetic reasons, often resulting in light trespass, glare, skyglow, or wasted energy. Very few situations require uplighting for safety. Use uplighting only where necessary, and in these locations, use appropriate minimizing measures to reduce duration, intensity, etc. Provide local switching for infrequently used uplights, preferably paired with a timer switch so lights are not inadvertently left switched on. Recessed downlighting reduces skyglow and wasted energy. In this example, the use of vertical shielding to prevent horizontal light spill would further minimize potential light trespass and skyglow. The use of swivel-mounted floodlights (shown here) can result in improper aiming, which can result in skyglow, light trespass, and glare. Uplighting should not be used for aesthetic reasons, as in this photo. Uplighting can cause skyglow, light trespass, and glare.
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