20 KING ON OCCULTATIONS 



Hence the immersion and emersion respectively take place 9"6 minutes before and ih 

 09"2m after conjunction. 



From the Ephemeris we have 



H. 



Washington M. T. of conjunction 10 

 And difference of longitude = — 



Ottawa M. T. of conjunction = 10 



Ttierefore Ottawa M. T. of Immersion = 10 

 And " " Emersion = 10 



The angle of position of the star at immersion measured from the north point of the 

 moon's limb towards the east is the angle between the directions /( n and H4 or, *J4°, pi 

 and n being the final positions of the moon and the observer at the calculated instant of 

 immersion. 



Similarly for emersion the angle is that between the directions }x'n' and H4 or 283°. 

 The angles of position from the vertex of the moon's limb are the angles between }x n 

 and Cn and between /('tt' and 6'// or 52|^° and 243° respectively. 



The working out of this example by the usual method of calculation throughout, 

 would be as follows : — 



H. M. 



Washington Hour Angle at Geoc. Conjunction ^ ir= + 59-9 

 Longitude of Ottawa . . . =±: A = — 05*4 



Ottawa Hour Angle . . . = H— A = + 1 05-3 



"&' 



Ai-guments : - 



J- From Downes' Table in American Ephemeris r = + 31 



= 4-57 



i> = 45° 23 J M. H. M. 



T — 30 = 01 

 T + 30 = 1 01 



M. H. M. 



Eeduced to Sidereal Time r — 30 = 01-003 



T + 30 = 1 01-167 



And for approximate time of 



Immersion— Hour Angle 0^ = 1 05-3 + 01-003 = 16°-576 

 Emersion " " W, = 1 05-3 + 1 01167 31-617 



Also for this approximate time 



Of Immersion x = JS:-j-x'X~ = + 0-0095 

 y=Y+y' X ^ = + 0-3605 



Of Emersion œ = X+x'X^= + 05781 



60 



y=Y+y' x^= + 0-4023 



