Calculation of Occultatiom 



ira 



62» 2' 

 - 32 38 



Par. orb. angle 29 24 



62° 2' 

 37 40 



24 22 



ii. To the proportional logarithm of the horizontal parallax, 

 properly reduced, add the logarithmic secant of the appa- 

 rent altitude, obtained from the approximate parallax in alti- 

 tude ; and first the secant and then the cosecant of the paral- 

 lactic orbital angle in each position. The first results will 

 give the parallax reduced to the true orbit, and their difference 

 will give the correction of the hourly motion in the orbit. The 

 difference of the second results will be the tangent of the an- 

 gular correction, if the corrected hourly motion be made radius. 



*D. 





t'^* 



^^^' 



^^" 



^ 



^ 



EQVINOCTIAL 



Example. The proportional logarithm of the equatorial pa- 

 rallax at 12" is 5092, increasing to 5115 in 12 hours; con- 

 sequently at 10" 53"^ it is 5090, at 9" 53^, 6088, and 

 adding 8 for the ellipticity, since the latitude is between 47° 

 and 51° (Astr. Coll. II. ii. XIII.), we have 509a and 5096- 

 Then 



M 2 



