SECRETARY'S REPORT 175 



Hence this Atlas presents a photographic bibliography of past dis- 

 coveries so that identification can be made quickly and accurately. 

 The photographic plates taken expressly for the Atlas have now been 

 completed. They were taken with the Sclimidt telescopes at the 

 Boy den and Mt. Stromlo Observatories. Two sets of plates were taken, 

 one with a yellow filter and one with a blue filter. From these, 160 

 charts size 11 by 11 inches have been made. The charts made from 

 plates taken with a blue filter have identified on them all published 

 verifiable variable stars, over 2,000 in number, while the other charts 

 have identified on them all of the NGC objects, all star clusters, and 

 all emission objects for which positions have been published. In the 

 process of identifying past discoveries, 500 new star clusters were 

 identified. 



The SAO Star Catalog, initially reduced in the FK-3 system, has 

 been converted to the FK^. All the preparatoiy work for publica- 

 tion in book form has been completed.^ Dr. Veis and Mrs. Katherine 

 Haramundanis have begun the groundwork for a possible future en- 

 largement by compiling a bibliography of star catalogs and references 

 pertaining to them; determining approximate orientation angles for 

 1,231 galaxies ; and compiling a catalog of about 2,500 discrete radio 

 sources. 



Stellar theory. — The Astrophysical Observatory has becom.e a rec- 

 ognized leader in the application of modern electronic computers to 

 stellar models. In January 1964 the Observatory was host to an in- 

 formal 3-day international Conference on Model Stellar Atmospheres, 

 which provided an opportunity for workers in this field to discuss 

 their current researches. The conference was convened by Dr. Wliit- 

 ney and his associates. 



Extensive calculations of model stellar atmospheres are being con- 

 tinued by Drs. Eugene H. Avrett and Stephen E, Strom.^^ The grid 

 of models calculated during the past year has been very successful 

 in establishing an improved effective temperature scale for early-type 

 stars. The effects of individual lines and of line blanketing are now 

 being incorporated into the computer program. The first phase of 

 investigation of line formation under conditions of noncoherent scat- 

 tering has been completed. Solutions were obtained for the fre- 

 quency-independent line source function for a two-level atom. Of 

 greater importance, the necessary mathematical techniques have been 

 developed for the solution of a wide variety of line-transfer problems. 



Dr. Strom has investigated the validity of model stellar atmo- 

 spheres by means of comparing predicted continuous fluxes and spec- 

 tral lines with the corresponding observed quantities. He obtained 



See footnotes, p. 177. 



