Survey of Northeast Greenland. 107 
Determination of thread intervals 31/VIII 1907 (extract) 
Telescope east Telescope west 
a Urs. maj. | À Draconis 7 Cephei | В Cassiopeiæ 
д = 62° 15'11” | 6 = 69° 50'40” д = 77° 06' 51” д = 58° 38' 16” 
в 57208 ore bs 67203 | Dif. 2 | 51208 | DIE |8 51205 | Dift 
Е ВЕ А А ИЕН Falles Е 
1 21h39m198.0 | 645.6, 1 22h6m46s.0 898.2 | 6 |99h 16028.4 138в.6 | 6 |22h45m538,2 583.6 
2 | 5081328|2| 7 29.9 45315 17 11.3) 69.7/5| 46 22098 
3, 40 23.61000|3| 8 15.2 00.0] 4| 18 04.9| 16.1| 4 44.5 |07.3 
4 32.1|08.5| 4| 25.8 |10.6| 3) 21.0| 00.0) 3 51.8 00.0 
5 57.8 34.2|5| 9 00.1 |449|2| 19 296 68.6] 2) 47 21.2294 
6 41 29.8|66.2/ 6) 44.0 |88.8|1 20 37.1|186.1| 1 50 3 58.5 
thread intervals which at a given moment were required were taken 
by interpolation. They were computed in hundreds of a second. 
As the thread intervals are computed for the meridian transit, 
they do not hold good for transits outside it. For transits on the 
vertical of the polar star, this is of no practical importance (a few 
hundreds of a second). If one sees fit, however, one may easily 
compute the correction for the deviation from the meridian by using, 
as an argument at the interpolation, a fictitious declination [2] deter- 
mined by зес [0] — sec д sec a, where a is the azimuth in which the 
transit is observed. 
The principle for the determination of time in the vertical of a 
polar star is, briefly speaking, that a star near the Pole is used as 
a sort of meridian mark. In the vertical of this star corresponding 
to certain sharply indicated moments, the transits of an equal number 
of stars are observed e.g. two to three with “telescope east” and 
an equal number with “telescope west”. The method thus demands 
that the azimuth in the case of the pole star and the immediately 
succeeding equatorial star should be identical, in other words, the 
pole star being pointed (on the middle thread) the clamp and slow 
motion screw ot the horizontal circle must not be touched before the 
transit of the corresponding equatorial star. As the inclination of 
the axis, particularly in high latitudes, plays a great part as regards 
the accuracy of the determination for time (the level correction is 
— iseco) and as it is further particularly difficult in a low temper- 
ature, as mentioned on pp. 93—94 to determine the latter, great care 
must be exercised in the level observations. 
In order to be able to direct the telescope towards a star quickly 
and unfailingly, it was necessary to have tables for the rough 
computation of the azimuth of the pole star and the corresponding 
