in North Polar Distance and Right Ascension. 449 

 published at the end of the Greeenwich Observations of the 

 year 1798, wherein the argument is apphed to take out 

 the equation by double entry, induced me to compute new 

 tables for more readily finding it. The formula which 

 I deduced for this purpose, is expressed by - 1 ,22 x 5, 

 {%A\ + 'Lol^g. rg2)+8",33^ {^A\-Y^Z- ^; S,) ^ak'"S 

 the semi-axis major and mmor at 9' ,55 and 7 ,n re- 

 spectively. The table will therefore be easily computed at 

 any subsequent period, should the major and minor axis ot 

 the ellipse of nutation be hereafter determmed of different 

 values from that which has been used in the above tor- 



mulae. ' • . i i • 



In takins; out the equation of nutation, the algebraic 

 sum of the'two parts of the table, give the whole equation, 

 entering the first part of the table with sum ot^ the star's 

 right ascension, and longitude of the moon's ascend- 

 ing node ; and the second part of the table with the right 

 ascension of the star minus the longitude of the moon's 

 ascending node. 



Examples. 

 Example I. To find the nutation in north polar di- 

 stance for Arcturus, on July 1,1812. 

 Right ascension Arcturus 7' l°47'39" 



Longitude D ' S3 3 1 31 00 



:)f^J^+Long. J' a . 3 18 39 Parti -1^^.13 

 *'^i-Long. i' S . 2 16 39 Part II -8",11 



Nutation required .. . — 9",24r 



To find the deviation of Sirius in north polar distance on 

 July 1, 1812. ^ ^, 



Right ascension Sirius . . 3' 9^ 13 2b 



Long, i^ £3 5 1 31 00 



jjt'^i + Long. D' £3 .. 8 10 44 28 +1,13 

 *^^t-Long. })' £3 . 10 7 42 28 +6",60 



Deviation required ... + 7"'>73 



When the longitude of the moon's ascending node ex- 

 ceeds the star's right ascension, as in the last example ; 

 twelve signs must be added to the star's right ascension 

 before the subtr;iction can be made. 



These tables may be also applied to finding the deviation 

 of a star in right ascension, but in this they require a liule 



more 



