T I M 



From this same Table and the Table of R. A. of the principal star* 

 (tee Start, catalogue of), may also be found the time of a star's transit 

 over the meridian in mean solar time nearly without the aid of the 

 Naut. Aim. ; the rule being-, 



Star's R. A. sun's mean R. A. acceleration = mean solar time at 

 the time of the star's transit. 



To find the time of the moon or a planet's pasting the meridian,. 

 (Woodhouse.) 



Let the increment of sun's R. A. in 24&. be a. ; do. of a planet or the 

 moon be A : let also the difference between the R. A. of the heavenly 

 body and that of the sun at the preceding noon, expressed in sidereal 

 time, be t; then time of a planet's transit = 

 a- A , /a-A y 



'TST^tLlJCv 



Or when the planet is retrograde, time = 



In the caie of the moon, the time 

 A-a xA 



24 i + V, * 

 And in the case of a star, the time == 



Time error in, corretponding to any small giren error or variation in 

 the declination, latitude, or altitude. ( Woodhouse,) 



(1) Declination* 



Let t be the exact time from noon, 3 = change of declination, i = 

 variation in the time, then 



= & (tan. declination X cot. t tan. lat X cosec. 



This formula is used in finding the time from equal altitudes of the 

 un, when there is a change of declination, in the interval between the 

 two observations, which there is always, except at the solstice* 



(2) Given the error in latitude to find the error in time. 

 Let A = error in latitude, i = do. in time, then 



* .= \ (tan. dec. X cosec. t tan. lat. X cot. t.) 



Thia formula is useful at sea; for between the observation which de- 

 termines the latitude from the sun's meridian altitude, and the observa- 

 tion of the altitude, the observer, if on board ti ship, may hare changed 

 Us place, UB if rosy have probably changed kit latitude, 



