158 



Astronomical aud Nautical Collections, 



log cos a 1= 9.9880, log sin « 9.3650, log cot ^ .9161, and log 

 ta 9.0839 : then 



The factor for the AR, being negative, we add 6 signs to the 

 angle, in order that the signs of the sines may be inverted, and 

 we have 6* 3° 9' for the angle. The angles never varying 

 much from those which belong to the lunar nutation, the two 

 series serve as checks on each other in the computation. For 

 reducing the factors into time we subtract log 15 — 1.1761, or 

 add 8.4614, instead of 9.6375. The angle for correcting the 

 declination is 14° 33', but the tangent being negative, the true 

 angle to be employed is 12"— (14° 33') or 6" — (14° 33'), since 

 the tangents are the same for opposite points of the circle ; and 

 by reverting to the original expression, we shall find that the 

 latter must be taken in this case : but for the correction of 

 the N. P. D. we take the former, when the declination is 

 north, in order to change the sign of the sine. The factor for 

 the declination is nearly constant for all the stars, and may 

 safely be assumed 9.62, which is equivalent to ",4 or ",41 for the 

 whole table, the error seldom amounting to so much as ",01. 



