Principles of Celestial Navigation

A Day in the Life of a Navigator » Afternoon Sun Line

An afternoon Sun observation is routinely taken a few hours after LAN. Observation and sight reduction procedures are exactly the same as those that were done in the morning.

photo of afternoon Sun over ocean

Once again, a strip form includes all of the steps in the reductions.

strip form for afternoon Sun reduction

Chief Sheedy: The afternoon Sun line is often taken a few hours after local apparent noon. It is done in the same exact way as we completed the a.m. Sun line. At time 19:35, we took an afternoon Sun line. We are now ready to plot it. The bearing from our assumed position by DR is 32 degrees 21 decimal 5 North, 055 degrees 18 West. The azimuth is 272.4 toward the geographic position. 272 decimal 4, and draw through, mark arrow, and GP. In this case, it’s 3.2 minutes away. So we get 3.2 minutes of latitude, make a perpendicular line, and this is our afternoon Sun line. Then we’ll label properly: 1935, Sun.

screenshot showing Universal Plotting Sheet with 1935 Sun line, and running fix based on advanced lines of position