5. New moon (astronomical definition)

The co-ordinates R.A. and Dec. can be used to calculate the position of any celestial object with a very great degree of accuracy. The reason for discussing this co- ordinate system is that the definition of the instant of “New Moon” in astronomical terms is when the Sun and Moon have the same R.A. This instant is the ideal definition for the start of the New Lunar month. It is clear and unequivocal and does not depend on terrestrial location (Ref: 2). There is therefore no need for visibility criteria as it can be calculated very accurately, not only for the present time, but extending over many years. These calculations can also take into account the very small variation of the positions of the vernal equinox and the celestial pole. Against this background of precise calculation one needs to examine the reasons for the enormous variations in the start of the lunar months when the first visibility of the Moon is taken as the criteria.