NAVIGATION AT SEA - Piloting, varies from ship to ship depending upon the equipment available and the master preferences. A daily routine, called the day's work, is established by the master and the navigator. While details vary with the navigator a day's work is:
1. Plot of dead reckoning throughout the day.
2. Observation and reduction of celestial observations for a fix during morning twilight.
3. Winding of chronometers and determination of chronometer error.
4. Observation of the sun for a morning sunline.
5. Azimuth of the sun for a compass check, made at about the same time as a morning sunline observation. This could be an amplitude observation at sunrise.
6. Observation of the sun at or near noon. This is crossed with a morning sun line, advanced, or with an observation of the moon or Venus to obtain a noon (ZT 1200)position.
7. Computation of the day's run (noon to noon, or midnight to midnight).
8. Observation of the sun during the afternoon. This is used with the advanced noon sunline, or with a moon or Venus line.
9. Azimuth of the sun for a compass check. This is made at about same time as an afternoon sun observation.
10. Figure the time of sunset, sunrise, and twilight, and make a list of stars and any planets that are favorable for observation.
11. Compute the time of moonrise and moonset.
13. Use of GPS and any other available navigation aid on a regular hour.
It is good practice to observe the brightest bodies as they appear in the evening while the horizon is clear and sharp, and the dimmest first in the morning before they they fade. The normal practice of navigators is to observe stars in the eastern sky first. During morning twilight the eastern horizon clearly defined first due to the rising sun; the dim stars above this horizon fade from view first because of the brighter eastern sky. During evening twilight the eastern horizon becomes indistinct first due to the setting sun,during evening twilight the bright stars in the eastern sky will be visible first. When taking sights I like to use Pub. No. 229 with the Nautical Almanac.
It is good practice to compare the gyro repeaters with the steering compass each half hour and after each change of course at sea, to detect any discrepancy. When checking don't overlook changes in variation and deviation. The master gyrocompass should be compared with its repeaters from time to time.
One of the duties of the navigator is to inform the captain of crossing time zone boundaries. The change of time is usually made at a convenient hour near the time of crossing a boundary, or during the night. On some ships the change is divided equally through several watches, as 20 minutes during three consecutive watches.
It is common practice for the captain to maintain a night order book. Standing orders such as the conditions under which the captain is to be called, and to keep a sharp lookout, are usually given on the inside front cover. The orders for each night, are recorded in order, along with his signature. Some of the items such as courses to be steered, speeds to be used, times and bearings of lights to be sighted, and any other pertinent navigational information. The navigator provides the captain with such information as he may require.
