By Louay J. Fatoohi, F. Richard Stephenson & Shetha S. Al-Dargazelli Department of Physics, University of Durham
When the distinguished French astronomer Andre Danjon was the director of Strasbourg Observatory, he became engaged in determining the light curve of the Moon. In 1931 he noticed that the Moon of August 13, which was only 16.2 hr before new, extended only 75-80° from cusp to cusp. In other words, Danjon found that the outer terminator of the crescent was considerably less than a complete half-circle, which it should have been theoretically. This was not an isolated observation because other observations, and also examination of previous records, showed that this shortening of the crescent was a general and real phenomenon. Danjon also noticed that the shortening diminishes as the angular distance of the Moon from the Sun increases.
By Bradley E. Schaefer*, !mad A.Ahmadt and LeRoy Doggettt
*NASA/Goddard Space Flight Center, Code 66I, Greenbelt, MD 2077I, t lmad-ad-Dean
Inc., 4323 Rosedale Ave, Bethesda, MD 208I4 and t Nautical Almanac Office, U.S. Naval Observatory, Washington, D.C. 20390 (Received I992 June 29; in original form I992 April 9)
We examine various claims of record and near record young moon sightings. We
find that the claims for 1916 May 2, 1895 July 22, and 1910 February 10 were made
under cloudy skies, hence the reports are likely to have an error in the date of
observation. Similar problems with the reported date have occurred for the claimed
sightings on I885 December 11, I989 May 5, and 1991 September 7· Other reports
from 1989 May 5 are shown to have reported incorrectly the moon’s position and
orientation, and so the observed source was not the moon. Of the reliable reports, the
record for sightings with the unaided eye is I 5·4 h by Julius Schmidt, while the record
for sightings with optical aid is 13 h 28 min by Robert C. Victor. We find that the
reliable reports can be sharply distinguished from the dubious reports based on such
factors as observer experience, promptness of report, and observer preparation.
By Bradley E.Schaefer NASA/Goddard Space Flight Center, Code 661 Greenbelt, MD 20771, USA
Prediction of the first visibility of the lunar crescent is a difficult problem involving astronomy, meteorology, and physiology. Historically, this problem has been attacked by an empirical approach where some set of observations is used to deduce a criterion for visibility. In this paper, I present a list of 201 observations and their observing circumstances for use in deriving and testing prediction algorithms. I find that criteria involving the moonset lagtime and the Moon’s age are quite bad in their predictive ability. Criteria involving the relative altitude and azimuth of the Moon at sunset are better, yet still can yield incorrect predictions within a zone of uncertainty with a width of over 105 degrees in longitude. The new theoretical model of Schaefer ( 1 988) is found to have a zone of uncertainty with an average total width of 47 degrees in longitude.