Astroislamica: Journal of Islamic Astronomy
Vol. 5 No. 1 (2026): Astroislamica: Journal of Islamic Astronomy (June)

The Sun's Vertical Depression Effect on True Dawn: A Visual Observation Study

Hariyadi Putraga (Observatorium Ilmu Falak Universitas Muhammadiyah Sumatera Utara)
Arwin Juli Rakhmadi (Universitas Muhammadiyah Sumatera Utara)
Ahmad Abdulwfa (National Research Institute of Astronomy and Geophysics (NRIAG))



Article Info

Publish Date
04 Jun 2026

Abstract

This study aims to analyze the influence of the Sun's vertical depth on the appearance of true Dawn in Medan City using the naked-eye observation method. Observations in Medan show that the true dawn light first appears when the Sun is at a depression angle of −14° to −12° below the eastern horizon. The difference between the visible true Dawn and the official dawn time (-20°) is about 6°. These results are consistent with more than 30 studies conducted across over 10 countries at various latitudes, utilizing approximately five different monitoring methods. These results confirm the need to correct the dawn time based on local observations and actual sky conditions, so that the determination of the time of worship better aligns with astronomical reality.

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Journal Info

Abbrev

ASTROISLAMICA

Publisher

Subject

Religion Astronomy

Description

Astroislamica: Journal of Islamic Astronomy is a journal that studies Islamic astronomy and Islamic laws related to astronomy. Astroislamica focuses on Islamic astronomy topics such as Qibla direction, prayer times, calendars, and eclipses through multiple perspectives, including Islamic law, ...