Sample Problem:
On February 25, 1981, at 0622 ZT, you observe the upper limb of the Moon with a sextant altitude (Hs) of 59° 58.9'. Your DR position is LAT 30° 28.3'S, LONG 102° 39.3'E. The chronometer reading at the time of sight is 11 h 21 m 18s and the chronometer is 48s slow. The height of eye is 59 feet and the index error is 2.5' on the arc. Determine the assumed position,
altitude intercept, and azimuth of this sight?
STEP 1
Skip the altitude corrections for now. Using GMT, and Greenwich date of observation, enter the Nautical Almanac and record tabulated hourly value of GHA, "v", TAB DEC., "d" corr and the
HP (54.2) and enter this information in your format
STEP 2
Turn to the yellow pages of the Nautical Almanac and find the 22 minute page,enter with 6 seconds.Then under the moon column find the increase in the moon's GHA since the last tabulated hourly value,you should get 5-16.4 enter this into your form.
STEP 3
While on the 22-minute page under the V' or "dO correction column, find the"d" (8.8) on the left-hand side. This is equal to + 3.3', enter this in your format. Next, find the "v" correction (14.8') which is = to + 5.6', and enter this in your format.
STEP 4
Compute your GHA of the Moon.
STEP 5
Compute the Dec. of the Moon
STEP 6
Compute the LHA using an assumed longitude
STEP 7
Now using the back of the Nautical Almanac, compute the sextant corrections. This will give the extra corrections required for obtaining Ho for a moon sight. Apply the index and dip corrections in the same manner as for star and sun sights. The altitude correction comes from tables located on the inside back covers of the Nautical Almanac.
STEP 8
Find the column 55 -59,then go down to 59 and intersect it with the left over minutes of your Ha
48.6 which is closest to 50.
STEP 9
Locate your HP closest to your, intersect it under "Upper Limb" column. This is your HP correction = 2.7'. Now total up the altitude correction, HP correction, and subtract 30' for upper limb. This is your total ALT CORR = 11.8'. NOW COMPUTE YOUR Ho.
STEP 10
Enter PUB 229 and finish working out the sight.
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