FIRST VISIBILITY OF THE LUNAR CRESCENT: BEYOND DANJON'S LIMIT

摘要

Many methods for predicting lunar first visibility have been proposed throughout history and new models are still being developed. All these models have to be compared with the published observations to test their validity.In this paper, we use our photometric model to predict the naked-eye first visibility of the lunar crescent. We find that an elongation of about 7 o 50 is the lowest naked-eye visibility limit. We also find that the lunar crescent may be seen - with a suitable telescopic magnification and ideal local conditions - when the Moon is about 50 from the Sun. Consequently, the thin lunar crescent may be seen in a telescope even at new moon when the Moon is at its greatest inclination.