APPENDIX 8 

 REPORT 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, 1939 : 



WORK AT WASHINGTON 



EECOMPXJTATION S 



The main business was the recomputation of all solar-constant 

 values since 1923, under the direction of L. B. Aldrich, referred to 

 in the two preceding reports. By the end of the fiscal year new 

 results had been computed for all available days since 1923 at all 

 stations. But the final corrections and general discussion still re- 

 mained to be done. Corrections had been applied, however, for 

 sky-brightness, ozone absorption, and all other conditions for the 

 results of Montezuma and St. Katherine for the years 1933 to 1939, 

 so that these values are definitive, except for the final reduction to a 

 uniform scale at all stations. This is to be decided upon when all 

 the work is done. It is expected that the entire recomputation will 

 be wholly completed by October 1939. A publication of the revised 

 work will afterward be made, funds for which have been generously 

 provided by John A. Roebling. 



The improvement in accuracy resulting from the revision is very 

 apparent when comparing Montezuma and St. Katherine daily re- 

 sults of the years 1933 to 1939, now practically final. Part of this 

 improvement results from the elimination of the radiation received 

 by pyrheliometers from the sky near the sun. We had always hither- 

 to treated this as negligible, but it was found to be a quantity 

 ranging up to about 0.5 percent and variable with the haziness pre- 

 vailing, A method was devised and applied for determining this 

 sky radiation. Its elimination from all the pyrheliometric observa- 

 tions since 1923 has been a considerable task, and has prevented the 

 completion of the revision of the solar-constant work by January 

 1939 as was stated in last year's report to be expected. 



A CX)NTBOVERST 



The Director spent much time in preparing a suitable reply to 

 an article by Dr. M. M. Paranjpe (Quart. Journ. Roy. Met. Soc, 

 July 1938). That author concluded : 



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