Night Sky Brightness Assessment in Nigeria Using Environmetric and GIS Technique

Abstract

High anthropogenic activities are rapidly increasing phenomenon and it is assumed to have global implications. In Nigeria, high anthropogenic activities rapidly increase above the standard of the threshold values especially the lighting sources. This increase due to the vastly growing of industries, residential and commercial uses and other sources such as street lighting in urban and semi-urban areas, which can make the night sky brightness in the area above the threshold set for polluted status. The study measures the night sky brightness at the most densely populated urban centers of Nigeria; to estimate and quantify the level of the night sky brightness from the sites nearby the cities of the planned research study. The research monitored the zenith sky brightness from November 2015 to March 2016 using Sky Quality Meter (SQM). However, typical values ranging from 20.14 to 22.00Mag.sqm /arc sec.2 were measured at different sites of the study area. This data recorded in the field was analyzed using Agglomerative Hierarchical Method via Ward’s Methods to cluster our data according to the pollution status of the areas. Result showed three clusters in which class 1 has low pollution; class 2 is moderate while class 3 has the high pollution status. The sites classified in class 3 are more polluted due to the high use of artificial light. However, geographical information system (GIS) software was employed to confirm the results obtained from environ-metric technique and concluded that this result is confirmed to be the same. Hence, it illustrated that sites in cluster 1 have an excellent dark location that can be used to build optical observatory stations and other astronomical observations due to their dark sky.