22 KING ON OCCULTATIONS 



H. M. 



Washington Mean Time of Geocentric Conjunction = 10 457 



T — 30m + 01-0 



p — fy = — 10-8 



Negative Longitude = + 5'4 



Ottawa Mean Time of Immersion . . 10 41'3 



i = + -2007 '/ = + 0-4376 



(jp — g)f' = — -0319 (p — 9)^7' = — 0-0032 



X= + -1688 H= + 0-4344 



log -1688 = 9-22737 

 log -4344 = 9-63789 



log tan P = 9-58948 



Angle of Position from the North Point = 74°-2 



P = 21-2 



Angle of Position from Vertex 53-0 



Comparing the results by the graphical with those by the logarithmic method, we 

 have 



By Graphical Method By Logarithms 



n. M. n. M. 



Time of Immersion . 10 41-5 10 41-3 



Angle from North Point . 74° '74°-2 



Angle from Vertex . 52^ 53 



Calculating the Emersion by logarithms in the same way we have the resirlts 



H. M. 



12 00-3, 282°-8, and 243°-0 

 against 12 00 3, 283°, and 243° as found by the graphical method. 



As another example, take the occultation of 80 Virginis, 24th April, 1888, at Kam- 

 loops, B. C. Here we get as results by the graphical method : — 



H. M. 



Mean Time of Immersion 11 59-3 

 " Emersion 12 43-0 



Position angles from the North Point 66°-75 and 347° 



The corresponding results by logarithms are 



H. M. 



Mean Time of Immersion 11 59-5 

 Emersion 12 43-6 

 Position angles 66°-57 and 347°-45 



As compared with the graphical method, that by logarithms has the disadvantages 

 of being much longer, and aflfording greater opportunity for mistake, angles in all four 

 quadrants being dealt with. Further, when the computed time falls far from the assumed 

 time, a complete new calculation is required, which is avoided in the graphical method. 



