Abstract

The first part of this dissertation investigates methods of predicting the first visibility of the lunar crescent: an astronomical problem that has attracted the interest of man since ancient times. Many early nations used lunar calendars, the months of which began on the evening of the first sighting of the lunar crescent after conjunction. In modern times, the resolution of this astronomical problem is of special importance -both for historians who need to determine ancient dates exactly and for Muslims around the world, whose religious calendar is lunar. The interest in this matter over the centuries has resulted in the appearance of a number of solutions by a variety of authors for predicting the first visibility of the lunar crescent.

The purpose of the first part of this dissertation is to assess the accuracy of these prediction models using ancient, mediaeval and modern observational data and to explore possible improvement. The study concludes that the concept of a “zone of uncertainty” must be incorporated into any lunar
visibility criterion; it further applies this conclusion to the widely used modern criterion of true lunar altitude versus azimuthal difference between the sun and moon. The observational data show that developing a “zone of uncertainty” in this particular criterion yields the best results of all.

The second part of the dissertation is an investigation of six problems in historical astronomy. These are: (i) assessing the accuracy of solar eclipse observations made by Jesuit astronomers in China; (ii) assessing the accuracy of lunar eclipse observations made by Jesuit astronomers in China; (iii) dating the solar eclipse of Thales; (iv) determining the modern equivalent of the Babylonian angular units of measurement; (v) dating the eclipses of Thucydides; and (vi) dating the solar eclipse of Plutarch. All papers have been published or are currently in press.

Original download link: First visibility of the lunar crescent and other problems in historical astronomy. – Durham e-Theses

Abstract. 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.

Introduction The lunar crescent visibility has been studied by many astronomers since the Babylonian era, with as a result currently more than 12 different criteria for lunar crescent visibility, based on a number of sightings in different lunar conditions. Many of these criteria were developed by Islamic astronomers, since a number of Islamic religiouseventsaredirectlyrelatedtolunarcrescentsighting.Forexample,thenew Lunar (Hijric) month begins on the next day of sighting the new crescent at west after sunset.

Download HERE New Criterion Crescent.pdf