Abstract:
The single parameter criterion of Yallop (1998) is considered as most authentic guideline for earliest visibility of new lunar crescent for amateur astronomers and the common people searching the new crescent for calendarical purposes. Yallop’s criterion is based on the data deduced from Bruin’s visibility curves (1977). Bruin developed his curves considering average brightness of the full moon close to the horizon while assuming the crescent as a small disc based on the theory of extinction due to Bamporad (1904). He also used the average brightness of the twilight sky that makes Bruin’s visibility curves highly approximate. In this work the minimum magnitude/brightness of twilight sky has been considered for crescents of various widths that were reported seen, taking into account the elevation above see level the local temperature and relative humidity in the with the algorithm due to Schaefer (1998). Magnitude/brightness of the crescent has been compared with the brightness of the sky to develop the visibility curves and the minimum visibility curves. These curves have lead to a new lunar crescent. Analyzing the criterion on the basis of more than 450 evening crescents observations reported by Odeh (2004) new visibility ranges have been suggested and the best time of visibility has been modified.
Page(s):
1-16
DOI:
DOI not available
Published:
Journal: Sindh University Research Journal, Volume: 42, Issue: 1, Year: 2010