The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Publications Copernicus
Articles | Volume XLII-4/W1
29 Sep 2016
 | 29 Sep 2016


S. Anwar, K. M. Omar, and M. S. Che Awang

Keywords: Imkanur Rukyah, Hijri Calendar, New Moon Visibility

Abstract. The Imkanur rukyah criteria can be defined as the minimum limit in expecting the new moon’s visibility in determining the beginning of Hijri months. It has been used in the development of Hijri calendar in Malaysia since 1992. Based on the criteria, the new moon is considered visible if the altitude at sunset is at least 2° and the elongation between the moon and the sun is at least 3°, or at moonset, the age of the moon is at least 8 hours. The altitude limit of 2° and the elongation limit of 3° indeed were determined according to the data of new moon visibility observed in Indonesia, whereas for the 8-hour moon’s age, there is no written rule regarding to it. The use of the moon’s age criterion as an alternative to the geometric criteria can lead to confusion if both conditions provide different results. Therefore, this study was performed to assess the relevance of using moon’s age as an alternative in Imkanur rukyah criteria used in Malaysia. The study utilised the data of the sun and the moon’s positions, the time of sunset, the time of moonset and the time of conjunction (new moon). The data for the sun were calculated based on VSOP87 theory, while for the moon, using ELP2000-82b. Based on the analysis, in determining Hijri dates from 1996 to 2015, there are 22 discrepancies found between the moon’s age and the geometric criteria, in which, 5 of them occur in the month of Ramadan, Syawal and Zulhijjah. These conditions show that the moon’s age criterion is not always consistent with the geometric criteria. Therefore, the use of moon’s age as an alternate criterion in determining the beginning of Hijri month is considered irrelevant and should be further reviewed.