Royal Astronom ical Society. 24 3 



Stars contained in the Royal Astronomical Society's Catalogue. By 

 the Honourable John Wrottesley*. 



Of the stars contained in this catalogue, seventeen had been 

 wholly, or in part, observed at the time Mr. Wrottesley's former 

 catalogue of 1318 starsf, for which the gold medal of the Society 

 was awarded in 1839, was in course of observation, but are not in- 

 cluded in that catalogue. The remaining thirty-eight are selected 

 from the first list of stars accompanying Mr. Baily's " Address to 

 Astronomical Observers," May 1837 ; and such were chosen as had 

 not been previously observed at the author's observatory, or had not 

 been observed at all since Piazzi's time, or presented discrepancies 

 the clearing up of which seemed most likely to prove interesting. 

 The observations of these thirty-eight were begun in May 1837, 

 and carried on until August in the same year, by Mr. Hartnup ; they 

 were resumed by Mr. Wrottesley himself in December 1839, and 

 concluded in August 1840. In every case the observations were 

 continued until six or more of each star had been procured. In ob- 

 serving this catalogue all possible care was exercised that the mean 

 places of the stars comprised in it should be entirely unaffected by 

 any errors arising from imperfect instrumental adjustment. With 

 respect to the standard stars employed, in 1837 only a few were 

 used, sometimes only one, but care was taken that it should be si- 

 tuated very near the parallel of declination of the catalogue star. 

 In 1 840 all the Greenwich stars were used indifferently, that pass 

 the meridian to the south of the zenith, and are comprised in the 

 list of those with which the former catalogue was compared ; and 

 usually from five to six, and sometimes as many as from eight to ten, 

 were observed on the same day, and the mean clock-error resulting 

 therefrom used in deducing the catalogue stars. Bessel's right 

 ascensions of these standard stars, and Mr. Wrottesley's own place 

 of Fomalhaut, have been invariably used in reducing the catalogue 

 stars ; so that this catalogue, as well as the preceding, is founded 

 on Bessel's mean places of the Greenwich stars. In an introduction 

 to the catalogue, the author has explained in detail the different 

 methods which he employed for determining the errors of level, col- 

 limation, and azimuth, and the other corrections applied in the re- 

 ductions. The performance of the transit- clock during the pro- 

 gress of the observations was satisfactory ; for though the rate was 

 at times considerable in amount, it was always uniform. As a test 

 of the extent to which the catalogue may be relied on for accuracy, 

 Mr. Wrottesley states, that out of the forty-three stars contained 

 in it, which have been observed by Mr. Airy, in no one case does 

 the difference of the results, for a star more than 25° from the pole, 

 exceed 8, 17. 



Postscript to Mr. Baily's Report on Mr. Maclear's Pendulum Ex- 

 periments:]:. By Mr. Baily. 



» Now Lord Wrottesley, and President of the Society. 



f See the Monthly Notices for November 1836; [or Phil. Mag., Third 

 Series, vol. x. p. 2270 



J Read at the meeting of the Society in June 1840, [See vol. xviii . 

 p. 602.] 



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