And the aberration in longitude 

 -20". 282 x <'" 



co.s lat, 



If A be the right ascension, and D the declination of a star, L being 1 

 the sun's longitude as before, the aberration in declination is 



in. D ( 19". 17 sin. (A L) o". 83 sin. (A -f- L)) 8" cos. L X cos. D. 

 And the aberration in right ascension is 



_ 19" 17 X cos. (A L) o". 83 X cos. (A 4. LI 



cos. D 



From these four last Formulae all the effects of aberration may be 

 .computed. 



5. In consequence of the aberration of light, the apparent place of a 

 star Avill trace out upon a plane parallel to the ecliptic a circle, in which 

 the true place of the star is similar to that of the sun in the circle des- 

 cribed on the axis major of the earth's orbit as a diameter. 



This circle, projected upon the plane of vision, is an ellipse, the | ax. 

 maj. 20" 232, and ax. min. = 20" 2 3 2 X sin. star's lat. Hence a star 

 in the pole of the ecliptic describes a circle, and a star in the ecliptic a 

 straight line. 



6. To make allowance for the aberration of a planet, let T be the in, 

 ?tant for which the geocentric place is to be computed, t =. time light 

 takes to move from the planet to the earth. Compute its geocentric 

 place by the common rules for the time T #, and it will be its geocen- 

 tric place at the time T, corrected for aberration. 



The aberration of the sun in longitude always = 20", that being the 

 space moved through by the sun or earth in 8'. 7f ", which is the time in 

 which light passes from the sun to the earth. 



7. Aber ratio Curve. (Wright's sol. Camb. Prob.) 



Let y and p denote the rad. vect. and perpendicular upon the tangent 

 of the given orbit; y and p' the corresponding ones to the aberratic 

 curve. Also let c twice area described dat. tern. ; then 



These two equations will give the equation to the aborratir curve. 

 EJC. 1. Let the given orbit be a parabola ; then p 2 ~- (L lat. 



c 2 r I , T 



rect) .'. y' = j = ~J^, = 2 / 



3 



