APPENDIX 8 

 REPOKT ON THE ASTROPHYSICAL OBSERVATORY 



Sir : I have the honor to submit the following report on the activities 

 of the Astrophysical Observatory for the fiscal year ended June 30, 

 1941: 



WORK AT WASHINGTON 



Messrs. Aldrich and Hoover, with assistance of computers Mrs. A. M. 

 Bond, Miss L. Simpson, and Miss N. M. McCandlish, prepared in 

 manuscript the immense table of daily solar-constant observations 

 from 1923 to 1939. The table contains all individual observations 

 in detail for the three stations, Montezuma, Table Mountain, and 

 Mount St. Katherine. A single day sometimes involves in itself alone 

 a subtable of 10 lines, 10 columns wide. Every solar-constant deter- 

 mination was scrutinized in detail from the original records before 

 entry into the great table, and in very many instances recomputed to 

 check discordant results. Mean values giving the most probable result 

 of each day at each station were computed, and all were plotted on an 

 extended scale. This plot made up a roll about 15 inches wide and 

 200 feet long. 



In this form every day's values were scrutinized by C. G. Abbot, and 

 discordances noted. As one result of his work in preparation of a 

 paper entitled "An Important Weather Element Hitherto Generally 

 Disregarded," ^ Dr. Abbot had been strongly impressed by the fact 

 that the solar variation is several times greater in percentage for blue- 

 violet rays than for total radiation. This led him to investigate 

 whether on discordant days the shorter wave length parts of the 

 energy spectrum of the sun, as computed for outside our atmosphere, 

 were also discordant. It proved that in many cases they were not, 

 showing that errors had been made in other than the spectral parts of 

 the determinations. Hence, the entire great table was gone through, 

 and for all discordant days the blue- violet extra- atmospheric spectrum 

 was reduced to comparable units by bringing all days to equality in 

 the infrared region, where solar variation is nearly nil. Nearly a i 

 hundred pages of newly computed manuscript tables were required 

 to set forth this information. 



With this new information available. Dr. Abbot in many cases 

 marked "improved preferred" daily values on the great chart for one 



» Smithsonian Misc. Coll., vol. 101, No. 1, 1941. 

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