G.M.T. Zenith Distance Diff. True Bearing.
0800 87°47'.5 53'.8 247°55'
0805 8841.3 53.6 24708
0810 8934.9 53.1 24621
0815 9028.0 53.0 24534
0820 9121.0 52.5 24446
0825 9213.5 24358
The time of setting for Venus may be interpolated or extrapolated by the above table for the following factors:-
(a) At sea level with no refraction, $ \mathbf{Z}.\mathbf{D}.=9 0^{\circ} 0 0^{\prime} $
$$
3 4 ^ {\prime}, \mathrm {Z} \cdot \mathrm {D} _ {\bullet} = 9 0 ^ {\circ} 3 4 ^ {\prime}
$$
(c) At 8,000 feet and no refraction, Z.D. = $ 9 1^{\circ} $ 28'
(d) At 8,000 feet and refraction of $ 4 0^{\prime} $ , Z.D. $ = 9 2^{\circ} $ 08'
The allowance for refraction at 8,000 feet is generous, in that a table in the Air Almanac gives a refraction of about $ 1^{\circ} $ 40' for altitude 8,000 feet, and would make the time of setting much later, since a Z.D. of $ 93^{\circ} $ 08' is then required.
4. POSITION LINES FOR SETTING TIMES OF VENUS:
While the accuracy of data in Section (3), has been verified by various partial checks, it may be argued that since they apply to only one point, the results may be different for other points. To cover this contingency the following lines for equal times of setting (or position lines for given zenith distances at given times) have been calculated. They have been calculated for a height of 8,000 feet (dip 88') but no allowance for refraction. Variations in the times of these position lines for various factors can be allowed for in conjunction with the table in Section (3).
G.M.T./Lat.35°S 36°S 37°S 38°S 39°S 40°S
0800 176°58' 177°35' 178°09' 178°44' 179°20' 179°57'
0805 17543 17620 17654 17729 17805 17842
0810 17428 17505 17539 17614 17650 17727
0815 17314 17350 17424 17459 17535 17612
0820 17159 17235 17309 17344 17420 17457
0825 17044 17121 17154 17229 17305 17342
0830 16929 17006 17039 17114 17150 17227
For arguments of G.M.T. in the left hand vertical column, and latitude in the top horizontal row, the body of the table gives longitudes east of Greenwich.
Plotting these values on a chart exhibits quite clearly that Venus would be visible from the aircraft during the whole flight, except for any cloud that might be present.
5. ALTAZIMUTH CORRDINATES FOR SATURN:
Assumed position: Latitude 39 $ ^{\circ} $S
$$
\text {L o n g i t u d e} 1 7 4 ^ {\circ} 1 1 ^ {\prime} \mathrm {E}.
$$
No allowance for dip or refraction.
The assumed position of 1' further east was an accidental error