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R. H. Garstang (JILA, Univ. Colo. and NIST)
Joel Stebbins (1878 - 1966), Director of the Washburn Observatory of the University of Wisconsin, pioneered the use of photocells for astronomical brightness measurements. He seems to have been the first to use photocells to measure night sky brightnesses. He was a Research Associate of the Mount Wilson Observatory. During a visit to Pasadena in the winter of 1931-32 he measured the night sky brightness with a portable photometer on Palomar Mountain and at the Mount Wilson Observatory. The latter had begun to be affected by light pollution even at that early date. He does not seem to have published his results in detail, but reported them in a letter that he sent on 1932 October 5 to John A. Anderson, the Executive Officer of the Palomar Observatory Council. Donald Osterbrock recently found a copy of the letter in the Washburn Observatory archives, and kindly communicated the details to me for analysis. Stebbins' most important result was that the night sky near the North Pole at Mount Wilson was 0.38 magnitude brighter than the night sky at Palomar. He also stated that in the evening at Mount Wilson the sky at altitude 10º over Pasadena and Los Angeles could be as much as 5 times as bright as at the Pole. I have used my light pollution model to analyze these and other results of Stebbins. I estimate that the light emission of the cities in 1932 was about 220 lumens per capita. Using this emission I calculated the Mount Wilson sky brightness at 10º altitude over Pasadena and Los Angeles as about 5.4 times the brightness at the Pole, in excellent agreement with Stebbins. This light emission may be compared with 1000 lumens per capita that my earlier analyses indicated for 1970.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.