Observational study of lunar visible emission

An observational program using the Mount Wilson 60-inch telescope and a grating spectrometer was conducted to study visible emission on the moon. During six lunations in 1965, 24 lunar positions were observed under a wide variety of lighting conditions. Observations and data reduction were performed according to the method of line depths using both the H (3968 A) and K (3934 A) Ca II Fraunhofer lines. No line depth changes were recorded, that indicated presence of radiation of nonsolar origin with an intensity greater than about 5% of reflected solar continuum; changes corresponding to greater than 2% nonsolar radiation were observed only infrequently. Statistically significant variations in the line depths were found, however, in the range 0.5 to 2.0% and varied both in lunar location and in time. Some anomalous ratios were recorded at single lunar areas during single observations. The correlation of the variations of the H line with the K line was found to differ with lunar area studied. It was concluded that the line depth changes were the result of visible emission occurring on or near the lunar surface. Several phenomena may be present. Some evidence exists for small and temporarily varying amounts of emission over the entire lunar surface.