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Reducing Sights Using Pub 249
General
HO Pub 249, Sight Reduction Tables for Air Navigation and the Air
Almanac, can also be used to reduce sights. This method of sight
reduction is used by some navigators; however, the degree of accuracy is
slightly less than sight reduction by Pub 229.
Procedure
Once again, you would have to gather information to reduce; that is,
GMT, sextant altitude, and so on.
For our example problem, we will use the following data:
Date:
30 March 1985
Lat:
36° 40.1'N
hs:
40°
33.6'
Hgt of Eye: 50 ft
GMT:
06 26 21
Long: 017° 31.6' W
IC:
+ 0.8
OPNAV 3130/32
ACTION
Completed Strip
H.O.249 Air Alm
Form
Body
Enter the name of the body.
REGULUS
GMT
Enter time of sight.
06h
26m
21s
IC
Enter the index correction.
+ 0.8
D
Enter the dip correction (hgt of eye 50ft)
- 7.0
using the altitude correction table from the
Air Almanac. (See fig. 9-16.)
R o
This is the refraction correction from the
- 1.0
Air Almanac. (See fig. 9-17.)
SD
ha
Total Corr (sum)
hs
Ho
Total of IC, D, and R o.
- 7.2
Enter the sextant altitude.
40°
33.6'
Apply altitude corrections to find.
40°
26.4'
9-32
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