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A map of the normal albedo of the moon has been prepared by automatically measuring and raster-recording the optical density of a photoelectrically calibrated full-moon photographic plate. Calibration permits direct transfer of normal albedo (after reduction from the photoelectric signal recorded by the photometer) to the isodensity contours of the photographic image. On the night that the photog•raphic and photoelectric Observations were made, the lunar phase angle was 1.5°. Photoelectric observations of 182 points scattered across the lunar surface were correlated with the density of corresponding points on the photogravhic plate. Plate exposure coincided in time with the photoelectric photometry. The photographic emulsion-filter combination used provided a poorer approximation of the spectral bandpass of the Johnson photoelectric V magnitude than the emulsion-filter combination normally used for stellar photographic V; however, the spectroscopic emulsion used for stars is unnecessarily grainy and too fast for a photometric exposure. The moon's color is much more uniform than that of a field of startS; hence, the errors due to color effects that were introduced during calibration are insignificant. The photographic plate was transcribed as a density map at a scale of 1: 5,000,000, using a Joyce-Loebl-Beckman-Whitley combination densitometer and code tracer. Steps were taken to reduce random error by insuring uniformity of the photographic process. This random error was measured to be about 1 percent. The range Olf normal albedo was divided into 20 contour intervals, with extremes of 7 and 23 percent nt the 3" of arc resolution employed. Reliability of the map is assured because, for the first time, simultaneous photoelec-tric calibration was utilized and the plate parameters~ were demonstrably uniform. The map has already proven to 1 be of great utility in the fields of lunar geologic mapping and astronautical engineering.

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