154 OUTLINES OF NATURAL PHILOSOPHY. 







Occupation of Stars. 



152. The same method used in calculating 

 eclipses, may be applied to compute the occul- 

 tation of a fixed star by the moon ; only, when 

 the moon is distant from the ecliptic, the base 

 of the right-angled triangle in the former con- 

 struction, must not be supposed equal to the 

 difference of longitude, but to that difference 

 multiplied into the sine of the star's distance, 

 from the pole of the ecliptic, or into the cosine 

 of its latitude. 



If S (fig. 16.) be the star, D the moon, DE the diffe- 

 rence of latitude, SE is not to be taken as equal 

 to AC, the difference of longitude, but as equal to 

 AC X sin SP = dif. Ion. X cos A. 



The distance SD = V SE 3 -f DE% being thus 

 found, the rest of the computation is as before. 



If at the time of the mean conjunction of the moon 

 and a star, that is, when the moon's mean longi- 

 tude is the same with the longitude of the star, 

 their difference of latitude exceed 1 37', there can 

 be no occultation, but if the difference be less than 

 51', there must be an occultation somewhere on 

 the face of the earth. Between these limits there 

 is a doubt, which can only be removed by the cal- 

 culation of the moon's true place. VINCE, vol. i. 

 591: 



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