Title: New criterion for lunar crescent visibility Authors: MOHAMMAD SH. ODEH
A new criterion for lunar crescent visibility has been established using 737 observations, almost half of them obtained by the Islamic Crescent Observation Project (ICOP). This criterion is based on two variables, viz. the topocentric arc of vision and the topocentric crescent width. The new model is able to predict the visibility of the lunar crescent both for naked eye and optically aided observations. From the database we found a Danjon limit of 6.4 degrees.
Predicting the first visibility of the young lunar crescent for a given location is a problem that has challenged astronomers and mathematicians for more than four millennia. Numerous computational methods and algorithms for predicting the visibility of the lunar crescent have been proposed in the past (a comprehensive bibliography is given at the bottom of this webpage) but the method now most favoured by astronomers is based on the Yallop algorithm, proposed in 1997 by Bernard D. Yallop of the computing section of HM Nautical Almanac Office. Read more