4 
field of view and not shown in Fig.3 are the spiral lines for 
setting the overlap regulator by means of a drum on the RC8 control 
box, to which it is connected, to obtain the desired percentage of 
overlap from one exposure to the next for narrow angle (60°) and 
wide angle (90°) photography. For RC9 superwide angle (120°) 
photography, the passing of a terrain point from the forward to the 
back line marked "3" is timed in order to determine the exposure 
interval for setting in the Intervalometer. An image of a circular 
bubble is displayed in the black ring, in which it is centered for 
verticalising the principal optical axis by means of two footscrews 
which tip and tilt the cardanic mount. The drift correction is made 
after levelling, using the central reticle line and with the ab 
jective pointed vertically downwards. In the forward-viewing po 
sition, the cover limits of strips of photographs flown with narrow, 
wide and superwide angle lenses are indicated by the sets of curved 
lines converging on the horizon aiming point. Levelling can of 
course also be corrected with the objective inclined for forward 
viewing, thus permitting continuous scanning of the heading, the 
edges of the strip and the strip itself. 
The magnitudes of the drift, tip and tilt movements introduced at 
the navigation sight are determined by potentiometers housed in its 
mount. They are transferred through a follow-up servo control system 
housed in the PNGl Servo Control Unit to three servo motors in the 
sealed frame of the Universal Mount. These servo motors then repro 
duce the same movements in that mount, the camera supporting ring 
being driven for setting drift, while the mount is raised or lowered 
on its footscrews to execute the omega and phi corrections. The 
zero positions of drift, tip and tilt of the Navigation Sight are 
correlated with those of the mount druing installation in the air 
craft. Adjustments are extremely simple to make through the PNGl 
Servo Control Unit. Rubber buffers insulate the mount from air 
craft vibrations. Two of the footscrews are hinged to permit change 
of filters in the aircraft without removing the camera from the 
mount, after unscrewing the collar holding the third footscrew to its 
footplate.