Reducing Sights Using Pub 249, Continued
H.O.249 Air Alm
Enter the GHA hour value of Aries from
the Air Almanac to the nearest 10 minutes.
(See fig. 9-18).
Enter the minutes and seconds value from
the interpolation tables of the Air Almanac.
Add GHA(h) and Increments (m/s).
+ - 360 (if needed)
a Long (+E, -W)
Enter the assumed DR longitude to arrive at
an even degree of LHA, add east and
LHA= Total GHA + (v/v or SHA for stars
and planets) +E or -W DR Long.
Enter the assumed latitude.
Enter Pub 249 volume I, with the whole
degree of LHA for REGULUS, record Hc
and Zn (last block). (See fig. 9-19.)
Drop down Ho from above.
Find the difference between Hc and Ho
(remember to use Ho MO To). In this
example, Ho is more than Hc, so its
named T for towards.
Enter the Zn (true bearing).
As you can see, using Pub 249 to determine a celestial LOP is a quick
process compared to using Pub 229. Keep in mind that some amount of
accuracy is lost.