128 I. P. Koch. 
in the error 41, of the approximated longitude. In this manner we 
arrive at the following terms for the determination of 41, ') 
Al, = Ze, where 
ar \ cosoCcospC., \ = DR 
f = {9.39675 } 4a т = { 8.22066 5 10€ TT 
The logarithms of the co-efficients indicated within { } hold 
good anywhere troughout the globe. For 44€ and Jöc the values 
of the observation moments are to be used: 
The computation of 41, gives in the case in question: 
— 
Telescope east 41, = -= 28.7; telescope west: Al, = -= 35.7 
mean value 41, = — 35.2, thus 
= 6 AT = eee a? 0147465. 
The trifling discrepancy between “telescope east” and “telescope 
west” in the above example is accidental; generally it becomes 
considerably greater, which is only to be expected under the un- 
favourable conditions of observation. 
There is consequently, as a rule, no occasion to work out the 
computation as circumstantially as in the example quoted. By 
looking upon the correction of the azimuths it will appear that one 
might very often dispense with the computation of parallax and 
collimation, as these quantities partly cancel each other when arriving 
at the mean of “telescope east” and “telescope west”. The justifica- 
tion of this manner of proceeding is, however, dependent upon the 
position of the observations in relation to the meridian and on the 
general accuracy of the observation. As regards most of the results 
quoted below the computation has been carried out in the abbrevia- 
ted manner. 
We have already mentioned that it is possible to use two stars 
in connection with the moon, in which manner the accuracy of the 
observation may be somewhat increased. On the Danmark-Ekspedi- 
tion this was only tried in a single case, but, on the other hand, 
according as we gained greater accuracy and routine, we several 
times observed two or three transits of moon and star on both 
sides of the meridian; this was e.g. the case as regards the five 
last-mentioned of the determinations of longitude given below. In 
the observation journal greater weight has been assigned to these 
five determinations than to the other ones. The results, however, 
1) WILLIAM СнАОУЕХЕТ: A Manual of Spherical and Practical Astronomy, 5th 
edition, Philadelphia and London, vol. 1 pp. 375—376. 
