(647 ) 



X = [9.993 7731.9] sin {v + 77° 37' 24"85) 

 y = [9.876 2012.2] sin {v — 20 58 31.25) 

 z = [9.832 7001.5] sin {v — 1 47 16.19) 



The coefficients in square brackets are logarithms; the quantity v 

 denotes the true anomaly of the comet. 



By means of the expressions above given the heliocentric coordi- 

 nates have been derived from 4 to 4 days for mean noon at 

 Greenwich ; the coordinates of the sun were taken from the Nautical 

 Almanac after having been reduced to the mean equinox of the 

 beginning of the year. In the reduction of the mean places to 

 apparent ones the aberration terms are omitted, because, as it is 

 known, the influence of the aberration for the bodies of our solar 

 system can be more simply accounted for by subtracting from the 

 times of observation the equation of light. In the- two following 

 tables which contain the apparent places of the comet in « and 

 Ó I have therefoi'e added in column iy for each date the equation 

 of liglit expressed in mean solar days. The 4"> column gives the 

 logarithms of the geocentric distance. As first date I have chosen 

 May 1=' because I had derived from a preliminary computation that 

 before that time there would be no chance to discover the comet 

 owing to its small apparent distance from tlie sun and its large 

 distance from the earth. The possibility did not seem excluded, 

 however, that by means of powerful telescopes or sensitive photo- 

 graphic plates the comet might be discovered in January 1906. 

 Therefore I have derived positions for that month and sent a short 

 ephemeris to Prof. Kkkutz, wlio in a circular has communicated 

 it to astronomers. To give a clear idea of the apparent orbit of the 

 comet and also because the published places wei'e not perfectly 

 correct owing to a small reduction error, I here shall give the 

 correct results from 4 to 4 days. Up to now (February 14) no tidings 

 about the discovery have arrived, at which we need not wonder 

 if we consider the cloudiness and especially the southern and 

 generally unfavourable position. 



The next table gives the apparent positions of the comet for the last 

 8 months of the year. The direct computations have been made from 

 4 to 4 days; between them one date has been interpolated taking 

 into account the fourth differences. 



As a measure for the probable brightness we generally calculate 



the quantity H =^ ——. Although on account of the irregular varia- 



tion of the comet's light it is not certain that the brightness will be 



45* 



