Modelling differences in Skyglow in rural areas from common luminaire designs
Dr Chris Baddiley, Scientific Advisor to the British astronomical Association Campaign for Dark Skies.
In the UK, Skyglow from the towns illuminates the sky right into the rural environment. Most young people have never seen the Milky Way. This work below has shown that with careful streetlight design, there could be a return of dark skies in rural areas.
A mathematical model has been written by the author that reads industry standard photometry files of streetlight designs and calculates reflections and scattering off surfaces into the sky and then the downward scattering as Skyglow. It gives results for any atmospheric visibility, view distance, view elevation and azimuth angle. Reflection off surrounds including verges is included in the calculation.
Different luminaires have been compared in similar circumstances and conclusions drawn about the benefit of certain designs. Studies include tilted Low Pressure Sodium SOX, Cut Off High Pressure Sodium SON in both polycarbonate and curved tempered glass types, Full cutoff flat glass SON, and the effect of changing to white light sources.
This is the product of many years of work in support of The British Astronomical Association Campaign for Dark Skies. It was a learning exercise for the author and is intended now as an educational tool for the benefit of the lighting industry, local authorities, planners and designers.
Presentations have been given to the UK Highways Agency. A Guidance note ‘Towards Understanding Skyglow’ based on this work, is to be published by the Institution of Lighting Engineers in September, coincident with their conference.
The presentation covers some skyglow photometry measurements, followed by a description of the skyglow model and the results obtained.