Quantification of Evening and Morning Twilight Angle in Malaysia: A Suburban-Rural Areas Comparison
Abstract
Studies on the effects of sunlight scattering during twilight phenomena yield information about solar altitude or twilight angle value for determination of Isha and Subh prayer times. This study set out to a quantify the evening and morning twilight angle based on long time observation and compare the similarities as well as dissimilarities of results obtained between suburban and rural areas. Hence, data acquisition was performed in selected areas throughout Malaysia from April 2018 to September 2019 by recording sky brightness readings during twilight every day, utilizing Sky Quality Meter Data Logger (SQM-LU-DL). Good data visualization criterion and third-degree polynomial models have been applied to the collected data to obtain the best data. This study has found that the tendency values acquired from observation data appear to be in the range -18o for evening twilight angle and -17o to -18o for morning twilight angle. Besides, there is no specific pattern that distinguished between twilight angle variations in suburban and rural areas. The only discernable difference is that suburban area with higher population density has given a wider range and variability in twilight angle values.
