REPORT OF COMMISSION V GV-7 
The geometry of the observing procedure is illustrated in Figure 2. Assume 
that exposures are made at a fixed zenith angle with azimuth angles of 0°, 
60°, 120°, 180°, 240°, and 300°. 
In making the exposures in a vertical plane, each of the zenith angles is pre- 
set on the zenith circle with the instrument leveled. Each exposure is referenced 
to radio time signals at opening and closing. The time interval of exposure de- 
  
  
  
gar 
pv Ad 
14 gen La 
\ 
RX 
9o° 
^v, (29 60° Zi 
unt NS ^ e > =o 
d / > S 
Zt {tei / ; 7 a 
vi NORTH —- ] Y 
| 
| | 
A 
TE 
HORIZO 
Fic. 1. Geometry of vertical observing procedure. 
pends on the relative aperture and focal length. Three stars are identified on 
each exposure defining a near-equilateral triangle and equal radial distances 
from the fiducial axes intersection. 
The stars are identified by comparison of the negative with a suitable star 
chart. The approximate right ascension and declination of the principal point 
are required for each exposure to facilitate positioning the negative on the star 
  
  
  
2 
ZENITH 
Zs X 
zt 
12 
eo > 60” ALMUCANY 60° 
o 
e x 
1 60° 
\ G 
\ i 
. (x, 
A --X „AA A 30 
9 -- / / —— 
- 300° 
2.3 SN. \ de / x 
z^ SS N y A Ne 
. V M6 A 3 
/ = 1 7 et x 
y Vi u/ L-- N \ 
- NORTH —— 
td AS frs 
8, 3 © 
n 12,0? mm o 
| P ! eo 
4o? 
aM 
HORIZON PL 
FrG. 2. Geometry of horizontal observing procedure.