256 



LUNAR CALCULATIONS. 



Example ;- 



half the difference of <hc (rue altitudes, and the remain- 

 der will be a logarithuiic tangent. 



5. Find the corrcsjioiulont logarithmic sine ; sub(ract 

 it from the before-mentioned half-sum, and thfe remainder 

 ■vvill be the logarithmic sine of hall" the true distance. 



We will work one of the cases given in the '• Requisite 

 Tables" by each of these rules. 



ExAMPLi:. 



Let the apparent distance of the moon from a 

 star be 89''. 58'. 6". the apparent altitude of the 

 star 5*^. 6'. that of the moon 84°. 46'. and her hori- 

 zontal parallax 61'. 18'.; what is their true dis- 

 tance? 



In this case the correction for the moon's paral- 

 lax and refraction taken from Tab. VIII. Requisite 

 Tables, is + 5', 30".; and that for the star's refrac- 

 tion from Table I. — 9'. 44".; so that their true alti- 

 tudes are 84°. 51'. 30". and 4^. 56'. 16". 



, , , The7i, by the First Rule. 



»— worked by f -^ 



ih« first rule: -Nat. COS. 79°. 40 1793746 



Nat. CO?. 89°. 58'. G". 



.000552" 



A.-... 



.1/88219 



Ar. comp. log. cos. 84° . 46' 1 .0399483 



5°. 6' 0.001722S 



Log. COS. 84°. 51'. 30" 8.9523977 



4°. 56'. 16". ...--...-. 9.9983855 

 Log. A „ T. 2524208 



Log^B 1.2448751 



xVat. COS. 79°. 55'. 14" 1750135 



B. nat 1757418 



Diff. 0007283 



==: nat. COS. 90°. 2\ 30". 3. tlie true distance. 



