Morning twilight measured at Bandung and Jombang

Abstract

Twilight divided into three categories namely, astronomical twilight, nautical twilight, and civil twilight. The three types of twilight can occur either in the evening or early morning. According to the U.S. Naval Observatory the three types distinguished by the depression (altitude of the sun below the horizon) for the evening or the morning twilight, −180, −120, and −60. Sky brightness measurements usually intended to determine the quality of the sky at some observation site or to determine the quality of the atmosphere by light pollution. Sky brightness data could be use for practical purposes such as to determine prayer times (Morning Prayer). This study describes the measurement of sky brightness using a light meter Sky Quality Meter. The measurements indicate the presence of different values and patterns in the twilight sky brightness. This variability highly determined by the weather conditions. Sky brightness shows a constant value shortly after the evening astronomical twilight and before morning astronomical twilight. Before the evening astronomical twilight and after morning astronomical twilight sky brightness showing continue changing.