clxxxvi 



OBSERVATIONS. 



E. OBSERVATIONS OF VENUS II WITH THE CRACOW MERIDIAN CIRCLE. 



VENUS II. 



Observations with the Oracoio Meridian-Circle. 



These complete the collection of such determinations of the positions of Mars and Venus as 

 have been found capable of employment for our purpose, extending from November 2, 1849, 

 to Septmber 8, 1852. 



7. OBSERVATIONS COMPARED WITH EPHEMEMS. 



The next step to be taken is the computation of the tabular places for the moment of 

 observation, and the comparison of these with the declinations observed. The course of this 

 computation and comparison may readily be followed by means of the appended tables, which 

 contain all those values which strictly depend upon the ephemeris, or upon computation ; the 

 term "computed place" being considered as denoting the apparent place of that part of the planet 

 which was actually observed (whether limb or center) deduced from the ephemeris for the point 

 and moment of observation. The mean of a nearly equal number of determinations of the 

 two limbs is, however, considered as an observation of the center, affected merely by the 

 influence of defective illumination. This influence might, in fact, have been disregarded for 

 Mars in every instance, although it has been brought into the computation as a matter of form. 

 Consequently the tables of "Computation for observations" afford for each observation the 

 tabular right-ascension, declination, parallax, semidiameter, and resulting declination of the 

 part observed ; and appended to these the residual error of the ephemeris, as indicated by the 

 observations. 



