7. The Morning Twilight Sight
In clear weather this should be primarily a sight for latitude, since the A.M. sun sight for longitude will follow it. A latitude by Polaris, and at the same time some star in one of the southern quadrants, as a check, will give admirable results.
8. The Dead Reckoning from Noon to Noon
If there is no change of course in the late forenoon, as is usually the case, the dead reckoning for the day's run can be figured any time before noon so that it will be all ready to hand in to the captain with the other noon data. It is much easier to lay this off on the chart than to go to the trouble of calculating it by Table 2, Bowditch. On the other hand, such a calculation checks the chart work and should be worked out if you wish to make "assurance doubly sure."
9. Distance Run During the Last 24 Hours
Here, again, an answer by chart and an answer by figures is a good thing to secure. As you become accustomed to your work you will find the answer by chart infinitely easier and quicker to get. It is just as accurate, too, if you lay the distances off carefully with the dividers and parallel rulers.
10. Distance to Destination
The same remarks as are made under (9) hold true here.
11. Set and Drift of Current
Find the difference between your D.R. position and your position by observation at noon, i.e., the course and distance from your D.R. position to your position by observation. The course is the set of the current, the distance the amount of drift, all of which is easily calculated by Table 2, Bowditch. This difference between the two positions is seldom due to current. It is due to all errors of steering and the like. But these are all ascribed to current, for the sake of convenience. This calculation of the current is seldom used now, particularly when steaming in convoy.