after Conjunction closed to Vernal and Autumnal Equinox
Novi Sopwanb, Moedji Rahartoa, Budi Dermawana, Dhani Herdiwijayaa
a)Astronomy Research Division, Faculty of Mathematics and Natural Sciences,
Bandung Institute of Technology, Bandung 40132, West Java, Indonesia
b) Astronomy Study Program, Faculty of Mathematics and Natural Sciences,
Bandung Institute of Technology, Bandung 40132, West Java, Indonesia
Abstract
The appearance of 2 similar moon phases will be occurred every 235 lunation or about 19 years, it is known a Metonic cycle. The appearance of very young moon crescent after conjunction which still can be seen through the naked eye called "hilal".
The overall characteristics of hilal closed to Vernal and Autumnal Equinox will be presented in this paper. The changing speed of the earth around the sun when the sun reaches the vernal and Autumnal Equinox will contribute partly to the appearance and visibility of hilal. We use the Islamic Lunation Variant Number (ILVn) of 65, 164 and 201 belongs to the group of Autumnal Equinox (AEG) and the ILVn of 34, 71 and 170 belongs to group of Vernal Equinox’s (VEG) hilal.
The limited sample of hilal with the case of hilal illumination fraction f = 1% and a condition that all hilal closed to the equinox. The hilal have a minimum elongation value of about 12 degrees and the relationship between the altitude differences between the sun and the moon, DZ, at the time of sun set and the azimuth differences between the sun and the moon, DAZ, DZ=0.55(DAZ)+11.98 for VEG and DZ=-0.35(DAZ)+11.27 for AEG.
Keywords: hilal, metonic, equinox, visibility
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http://xa.yimg.com/kq/groups/15609031/1466221921/name/Sopwan-ICMNS2-02-rev-00.pdf
Bonus:
Руми/Хилал: http://hojja-nusreddin.livejournal.com/433629.html
Руми/Исчезновенье: http://hojja-nusreddin.livejournal.com/727185.html
