VISIBILITAS HILAL DI INDONESIA

Research on crescent visibility in Indonesia has not been conducted yet systematically based on astronomical analysis to obtain the criteria of possibility of crescent sighting. While, the criteria are needed in determining the beginning of Islamic calendar, especially for Ramadhan, Shawal, and Zulhijjah. This analysis is conducted to overcome such a problem, by using documentation of crescent sighting during 1962-1997 in Indonesia. The results can be concluded as follows: Crescent sighting with low altitude tends to be reported from less then 3 location, likely due to misjudging of foreground object (e.g.lamp) considered as crescent. Misjudging of the crescent due to misidentification of planet Venus or Mercury is proved for low altitude crescent sighting. After eliminating foreground and background objects, it is obtained the criteria of crescent visibility in Indonesia; (1). Moon age should be big than 8 hours. (2). Moon-Sun angle should be big than 5,6 degree. (3). Moon-Sun altitude difference should be big than 3 degree (crescent's altitude big than 2 degree) for Moon-Sun azimuth difference of 6 degree, while for Moon-Sun azimuth litlle than 6 degree, it is needed more altitude difference. For Moon-Sun azimuth difference of about 0 degree, the altitude difference shoul be big than 9 degree