PEEDICTION OF OCCULTATIONS. 



In the prediction of an occultation for a particular place, the principal objects of 

 determination are, the instant of immersion, or of the star's disappearance behind 

 the moon's limb ; of emersion, or of the star's re-appearance ; and the points on the 

 moon's border where these appearances take place. 



The calculations, according to the method of the late Professor Bessel, are greatly 

 facilitated by means of the quantities T, H, p, q, p', q', given in the preceding list. 

 Those who may wish to consult Prof Bessel's origiaal paper on this subject, will find 

 it in Schumacher's Astronomische Nachrichten, Vol. VII., page 1 ; also in the Berliner 

 Astronomisches JaJirhuch for 1831, page 257. The process of computation is shown by 

 the following equations : 



d = Longitude from Greenwich, of the place, ■+■ East, — "West. 

 (p = Geographical North Latitude of the place. 

 <p'= Geocentric North Latitude of the place. 



r = Earth's radius at the place, or the distance of the observer's position from the 

 earth's centre. 



It is unnecessary to calculate <p' and r separately, as we have 



(1 — e^)sin<f» , coscp 



rsincp' = 



^/(l— e^'sin^cp) >/(!— e^'sin^fp) 



in which e denotes the eccentricity of the earth's meridians. 



1 — e^ 1 



The logarithms of „ . „ . = log A, and of — — — — = log^, derived 



from e = '081697, according to the latest determination of Prof. Bessel, may be taken 



from the following table, where the geographical latitude of the place is the argument, 

 c 



