Fig. 6 c. An Aviotar cone in a frame, which then was placed on the triangle 
fig. 5. 
two crossing files close above the camera place. For the installation of 
the camera a stable wooden floor was installed in the tower. The camera 
was mounted on a special triangle shaped supporting frame Fig. 5, 
which was placed over an opening in the floor. The frame was support- 
ed by three foot screws for the horizontation. Further there were two 
adjustable cross spirit levels. When the camera was placed in the frame 
it could be temporarily levelled with the foot screws of the triangular 
frame so that the focal plane frame became horizontal, see Fig. 6 b. In 
this position the spirit levels of the triangular frame were adjusted. 
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p 
V