DEPARTMENT OF MERIDIAN ASTROMETRY * 



Lewis Boss, Director. 



This report covers the period from September 1910 to September 191 1, 

 during which the meridian observations undertaken at our southern station 

 in San Luis, Argentina, were completed. At the close of observations in 

 January 191 1 about 87,000 complete observations in 654 series had been se- 

 cured. The transit circle was promptly dismounted, carefully packed, and 

 shipped to Albany, arriving in the latter part of April 191 1, presumably with- 

 out serious injury, though there has been no opportunity as yet for a defini- 

 tive test by refined instrumental determinations. The entire staff arrived at 

 Albany and reported for duty then or within the next two months. Prof. 

 R. H. Tucker resigned to take effect July i, in order to resume the position 

 which he formerly occupied at the Lick Observatory. Mr. R. F. Sanford 

 also resigned to take up work with the Mills Chilean Expedition, established 

 by the Lick Observatory at Santiago de Chile. 



It had been a part of the program for the expedition to San Luis to employ 

 a photometer equipped with a photographic wedge. The latter was kindly 

 provided by Professor Pickering. Differential observations of magnitude 

 are planned for all stars of our meridian-circle program for which the mag- 

 nitude had not been determined by the Harvard College Observatory either 

 at Cambridge, Massachusetts, or at Arequipa, Peru. This had not been ac- 

 complished, as originally contemplated, at the time when the meridian-circle 

 observations had been completed. The resignation of recorders and assist- 

 ants had reduced the force to a point where these photometer-observations 

 became impracticable, unless the meridian observations should be materially 

 curtailed. It was accordingly arranged to return the photometer to Albany 

 for the purpose of minor alterations and additions necessary to facilitate its 

 use, and to give opportunity to the observers who are to use it to acquire the 

 requisite familiarity with its peculiarities and in its manipulation. This plan 

 was carried out, and accordingly the instrument was set up at the Dudley 

 Observatory on a suitable pier housed in a small and convenient shed. The 

 instrument was placed in charge of Mr. Meade L. Zimmer as principal 

 observer, and Mr. William Hunt, of Harvard University, was engaged as 

 recorder. These two practiced diligently for nearly two months. They sailed 

 for Buenos Aires July 20, 191 1, taking with them the photometer, with sub- 

 sidiary apparatus. It is proposed to make the measures of brightness purely 

 differential, on the basis of the Harvard photometry as the standard. 



* Address Dudley Observatory, Albany, N. Y. Grant No. 680. $33,734 for investiga- 

 tions and maintenance during 1911. (For previous reports see Year Books Nos. 2-9.) 



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