V •' 



U6. - ■ ■ - A NEW METHOD OP 



so that the approximate right ascension and declination of any star, are 

 used as arguments of simple entry, to give the correction.* The annual va- 

 riations contained in La Caille and Mayer's catalogues, will be found inaccu- 

 rate at this time, because they depend upon the right ascensions and declina- 

 tions, which are variable quantities, and from the time that has elapsed since 

 the construction of these catalogues, (from forty to seventy years) these 

 quantities have considerably changed. It follows, that those stars ought to be 

 preferred whose right ascensions are founded on recent observations, or 

 which have been computed with reference to the changes produced in the 

 annual variation, by the motion of the equinoctial points, and the secular di- 

 minution of the obliquity of the eliptic.t 



When the transits of several stars are observed, it will not be necessary to 

 compute the correction for each star separately ; all that need be known, is 

 the mean right ascension of each star, for the beginning of the year, and it 

 will be sufficient to know the declination within one minute. The following 

 rules explain the method which I have adopted for reducing my observations : 



Rule. 1st. Add together the times of transit of all the stars per chro- 

 nometer, also all the mean right ascensions, and all the mean declinations for 

 the beginning of the year, and divide each sum by the number observed. 



Rule. 2d. From the mean of the times of transit, subtract the time per 

 chronometer of the moon's transit, the difference, when corrected for the rate 



* The argument is tabular No. (1.3362 x Sin. Am.) multiplied by tangent of star's declination, 

 and added to 3.0678.— Care must be taken in the application of the Sin. Am. which, in the tv/o last 

 quadrants, that is, between twelve and twenty-four hours, is minus. 



f These observations were written previously to the appearance in India of the lid. vol. of the 

 Mensoirs of the Astronomical Society of London, containing the admirable tables of Mr. Baily. 



