GUIDANCE | NIGHT-TIME ILLUMINATION Dark matters The SLL has published its first, full-blown lighting guide on illumination and the nighttime environment. Co-author Benedict Cadbury summarises the new LG 21: Guide to protecting the night-time environment, following a summary by Jill Entwistle A Lighting for nature Obtrusive light Guide to limiting obtrusive light to protecting the night-time environment. LG 21: Guide Londons Piccadilly Circus: the sources of light pollution and skyglow are many and various, including building exterior and interior lighting, advertising signs, shop windows and street lights 46 December 2021 www.cibsejournal.com CIBSE Dec21 pp46-47 Dark skies Supp.indd 46 26/11/2021 16:53