Survey of Northeast Greenland. 119 
azimuth thus become subject to a certain error, and the harmony 
with the azimuth computed by means of the star observation, which 
may be regarded as infallible, is rendered incomplete. The deviation 
of the two azimuths seems to suggest the correction of the supposed 
value of the longitude of the place. 
Preparation for the observations. 
Let us fix the approximated length at /,. Corresponding to the 
latter and based upon the data given in the Nautical Almanac under 
Moon-Culminating Stars, for Moon I or II U(pper) and for the 
Var. of CS В. A. and Decl. in one hour of Long. an approximated 
right ascension of the bright limb and an approximated geocentric 
declination of the centre of the moon are computed with an accuracy 
of about 07.1 and 1’ for the culmination at the place of observation. 
From Apparent Places of Stars, Moon-Culminating Stars (pre- 
ferably) or Occultation Stars a star is selected, the right ascension 
and declination of which approach as nearly as possible to the right 
ascension and declination of the moon. (In certain cases it is not 
а, №а, 
а а 
2 = = 
< % = 
4) a 5 
u m 
= = 
Fig. 5. 
possible to reduce the right ascension ditference to less than 15™ to 
20™; it must not be less than 2™, as in that case one cannot escape 
the clashing of the moon and star observations). 
In order to arrange the two observation sets — “telescope east” 
and “telescope west” — as symetrically as possible as regards the 
meridian one puts (Fig. 5) 
when the star appears first (ax < al): a€@+a*—d,, 
when tbe star appears last (ax >a@: а*ж-- а© = 4.. 
The clock correction being du, U, = ax + du becomes clock 
time for the culmination of the star. The object which is the first 
to appear is then to be observed in the first position of the instru- 
ment at the clock time U, +1}: d,, respectively U, + "2 d, east of 
the meridian. 
