ASTRONOMY. 



If a fixed star had an annual parallax 

 that was sensible, it would appear to describe 

 an ellipsis, of which the greater semi-axis was 

 equal to that parallax, and the semi-conjugate 

 equal to the same, multiplied into the sine of 

 the latitude of the star. 



The centre of this ellipse would be the place of the 

 star, seen from the Sun ; the conjugate would have 

 the direction of a circle of latitude, passing through 

 the star and the pole of the ecliptic. 



. IfL be the longitude, and X the latitude of 

 a star, of which the annual parallax, when a ma- 

 ximum, is p j then, if the longitude of the Sun 

 is S, the parallax of the star, in latitude, will be 



p sin X cos (L S) j 

 and its parallax in longitude 



_-sin(L S). 



COSX 



DE LAMBRE, Abrege, legon 19. 29. 



The effects of aberration and of parallax, are both 

 to make the fixed stars describe ellipses, but quite 

 different, in magnitude and position. BOSCOVICH, 

 however, has demonstrated, that a fixed star, 

 under the influence of both these causes, will still 

 appear to describe an ellipsis about its true place. 



Di$$ertati& 



