Semi-Empirical Modelling of Light Polluted Twilight Sky Brightness

Publication Issue: 
Volume 39, Issue 2, 2018
Page No: 
Date Received: 
Friday, February 9, 2018
Authors' Name: 
M S Faid
N N M Shariff
Z S Hamidi
N Kadir
N Ahmad
R A Wahab
Authors' Affiliation and Address: 
Academy of Contemporary Islamic Studies, Universiti Teknologi MARA, Shah Alam
Institute of Science, Faculty of Applied Science, Universiti Teknologi MARA, Shah Alam
Academy of Islamic Studies, University of Malaya
Faculty of Science, University Malaya
The phenomenon of twilight been stipulated as naturally dependent on the variables of solar depression, aerosol concentration and ozone composition. The unique colour spectrum of twilight is attributed to the ozone layer and aerosol, whereas its brightness is heavily relying on the altitude of the sun below the horizon. While all the natural dependent is being researched extensively, the impact of light pollution on the brightness of the twilight is not being explored thoroughly. Most of the model of twilight sky brightness such as Kastner [1] , Schaefer [2] and Belokrylov [3] only consider the factor of solar depression, aerosol concentration and ozone composition, while light pollution variable is not yet considered in the models. The objective of this study is to construct a model of light-polluted twilight sky brightness by understanding the alteration of light pollution towards the natural behaviour of twilight sky brightness. The model is constructed using Kastner expression of twilight sky brightness as a base, with the combination of data from Garstang[4], Berry[5] and 72 data of twilight brightness from various light pollution profile, utilised by Sky Quality Meter (SQM) TableCurve 3D and SigmaPlot. The model is then compared observation on rural light-polluted twilight brightness and found to have range of error around ±0.5 mag/sec2. It is the first attempt to express the light-polluted twilight sky brightness in mathematical formulation. The model, however, needs further refinement mainly on the analytical variables of light polluted twilight sky brightness to ensure its applicability on various locations.
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