The Effect of Full Moon Light on the Brightness of the Sky in Lhokseumawe City

Abstract

The brightness level of the night sky is a crucial factor that significantly determines the success of astronomical observations. Various light sources, both anthropogenic such as residential and industrial lighting, and natural such as moonlight, can substantially reduce the visual quality of the sky. This study specifically aims to examine the contribution of the full moon to the brightness level of the night sky. The instrument used was a Sky Quality Meter (SQM), designed to measure sky brightness in units of magnitude per square arcsecond (mag/arcsec²). Observations were carried out for three consecutive nights, from December 16 to 18, 2024, coinciding with the full moon phase. Data were continuously recorded from 19:40 until 06:20 the following morning to obtain a temporal representation of sky conditions. The results showed an increase in sky brightness, with average values ranging between 16–20 mag/arcsec². On the first night, the sky appeared generally brighter, possibly due to atmospheric or local factors. On the second night, brightness peaked near 20 mag/arcsec² before gradually declining, while the third night remained relatively stable around 18–19 mag/arcsec². These findings confirm that full moonlight significantly contributes to increased night sky brightness and hold important implications for planning astronomical observations.