Middle Age lunar crescent visibility criterion is criterion that was produced during 8th until 17th century. This includes al-Khawarizmi lunar crescent visibility criterion in 8th century until al-Lathiqi lunar crescent visibility criterion in 17th century. Numbers of review on mathematics and astronomy during the Middle Age, however the number of review that specifically written for Middle Age lunar crescent visibility criterion limited, with majority of review is written to study the historical of Middle Age science, astronomy, mathematics and geography as a whole, and not converge on lunar crescent visibility criterion. . Therefore, this article aimed to provide a review on Middle Age lunar crescent visibility criterion. The review is conducted using literature analysis, snowball literature search and specific inclusion and exclusion criteria. The review is performed based on 13 works on lunar crescent visibility criterion that pass the selection criteria. The review found out that most of the lunar crescent visibility criterion is based on al-Khawarizmi arc of separation and solar longitude, lunar crescent visibility criterion, with exception on Ibn Tariq, Ibn Qurra and Ibnu Yunus lunar crescent visibility criterion that adopt angular distance or elongation. The review suggest that a new outlook on Middle Age lunar crescent visibility criterion study can be done, by conducting an assessment on new data of moonsighting, and comparing with modern lunar crescent visibility criterion research.
The main challenge in the young crescent moon (YCM) observation is the ability to detect the appearance of the YCM, which has varying contrast due to the phenomenon of twilight. The advancement of technology in digital imaging helps the faint and thin image of the YCM to be detected and taken during observation. The techniques used in the observations of the YCM were naked eyes, telescope, and telescope with cameras. A digital imaging technique is also being used in the observations to assist in detecting and recording the image of the YCM more effectively. This paper presents the analysis of the YCM observation data recorded at Telok Kemang Observatory from 2000 to the present. A total of 275 observation sessions were conducted during this study, with 87 positive sightings successfully recorded. The studies found that the smallest elongation and the minimum altitude at sunset of the YCM successfully recorded were 6.81° and 5.40°, respectively. The moon was recorded at an altitude of 3.37°, while the sky is still bright with the sun at an altitude of –2.64° using the digital imaging technique. Based on the records, the YCM which has the minimum criteria of Imkanur Rukyah, i.e., altitude of 2° and elongation of 3° at sunset was never detected or recorded during the 22 years of observations. Therefore, this work suggests the need to change the visibility of Imkanur Rukyah criteria used since 1995 to a more potentially observable criterion. In other aspects, the lengthy observation activities have contributed to the development of a database system for JAKIM that other researchers can access.
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