LONGITUDE. 



Table IV. 



Example of one Day's Obfervations. 



^ -j- The figns are reverfed in the reduftion, becaufe apparent A.R. is deduced from the afTumed mean A.R. 



other ftars the mean A. R. is deduced from the apparent. 



In the 



In the above example the mean right afcenfion of « Aquilae 

 is aflumed 19' 41' 21. "75 for January i, 1807, and its 

 apparent right afcenfion is deduced ig"" 41' 25. "58 by 

 applying the correftions of Tables II. and III. The firft of 

 thefe include the effeft of preceffion, aberration, fdar nuta- 

 tipn, and proper motion peculiar to the ftar ; the fecond 

 gives the nutation, including the equation of the equinoftial 

 point, fo that the whole correftion, when applied, gives the 

 interval of fidereal time that fhould elapfe between the paf- 

 fage of the ftar and that of the apparent equinoftial point ; 



this interval is 19'' 41' 25. "58 ; and if the A.R. of the ftar 

 be rightly aflumed, it is the time which the clock fhould 

 mark at the interval of the tranfit ; but the clock marked 

 only 19'' 40' 55. "74. The difference is 29. "84, which we 

 call the error of the clock, and lince its rate is — 0.2S, we 

 can, by means of the above table, calculate the error of 

 the clock for every other ftar. For inftance Capella, the 

 decimal multiplier of which is 0.39, which is to be multi- 

 plied by the daily rate, — 0.28 x 0.39 = .109, which 

 added to 29. "84 = 29.95, '•''^ reduction correfponding to 

 X X 2 Capella, 



