Astronomical and Nautical Collection » 1 1 5 



The following is an example of a calculation of the longitude 

 from an observed right ascension of the moon upon the meridian, 

 compared with the ephemeris, by the rule given in the begmning 

 of this paper. 



On 15th April, 1818, the right ascension of the moon's first limb, 

 when upon the meridian of Greenwich, was observed = 



142° 11' 48" 

 Semidiameter in right ascension . . 16 32 



Right ascension of moon's centre . . 142 28 20 

 From the Connaissance des Terns, we have D A. R. 



1818 o , . 



April 14, Midn. 131 35 17 ^ , ,, 



6 31 54 , , 



15, Noon 138 7 11 4 45 , ,, 



6 27 9 4 38 



Midn. 144 34 20 4 32 



6 22 37 



16, Noon 150 56 57 



142 28 20 

 138 7 11 



As. a® 27' 9* : 4 21 9 :: 12^ 0' 0" 



A. C. Log. 6 27 9 = 5 633970 

 Log. 4 21 9=4-195041 

 Log. 12 = 4-635484 



4-464495 = Log. of 

 Approximate time at Paris 8** 5' 40' 



Equation of second difference + 'S0"'5 in time = 57_ 



Apparent time Paris = 



Sun's right ascension then = 



Righj; ascension of meridian at Paris = 



Observed R. A. of mer. at Greenwich 142° 1 V 48" = 



Longitude 9 255 



I 8 



