Naval Procedure:
Daily Procedure:
1) Calculate the morning nautical time (MNT) from the nautical almanac the night before.
This is the time when we take our readings.
2) At 45 min before MNT, recognise and identify the celestial bodies and fill up the table under Calculated.
3) At MNT, measure the altitude of the celestial bodies and fill up the data under the Observed section
For example:
|
Serial No. |
Stars/Planets |
Calculated |
Observed |
|||
|
Bearing |
Sextant alt. |
Gyro Bearing |
Sextant alt. |
D.W.T |
||
|
1 |
Betelgeuse |
43.1 |
66o 04.8’ |
|
- |
- |
|
2 |
Canopus |
160.6 |
43 o 41’ |
|
44 o 45.4’ |
05 18 24 |
|
3 |
Jupiter |
42.3 |
45 o 20’ |
|
49 o 53.6’ |
05 28 22 |
|
4 |
Sirius |
106.2 |
61 o 21.5’ |
|
68 o 18.2’ |
05 30 37 |
|
5 |
Formalhaut |
241 |
6 o 37.8’ |
|
- |
- |
Table of the commonly used 57 navigation stars for observation
A pictorial representation of the bearing and altitude of the stars with respect to the ship.
The largest circle represents the altitude 0 o .The middle circle represents the altitude 30 o
and the inner circle represents the altitude 60 o. The point above the ship represents 90 o.
4) Using the sun’s course to map out location on earth
A position plotting chart is needed to find out the ship's direction and the ship's eventual course.
|
Time |
Event |
|
Sunrise |
Measure sun’s bearing |
|
0830 |
Measure morning sun’s altitude |
|
1000 |
Calculate morning sun and plot Observed position (Sun Run Sun) |
|
1115 |
Prediction of merpass of the sun |
|
Merpass-15min |
Measure merpass sun’s altitude (Sun Run Merpass) |
|
1400 |
Measure afternoon sun’s altitude and bearing (Merpass Run Sun) |
|
1530 |
Sun Run Sun |
|
Sunset |
Measure sun’s bearing |
5) Predict the Evening Civil Time (ECT)
6) Identify the stars 15 min before ECT
7) At ECT, measure the altitude of the celestial bodies
8) Prepare the next day’s MNT
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