Principles of Celestial Navigation

A Day in the Life of a Navigator » Preparing for the Evening Observations

photo of evening nautical twilight, Waikiki Beach

Similarly to preparing for morning observations, a navigator needs to decide which objects will be visible, and which will give the best lines of position during evening twilight. The times of sunset and twilight are determined by using The Nautical Almanac; strip forms can be used to help.

As with the morning three-star fix observations, we can use either the 2102-D Star Finder or Pub 249 to find which stars are the best objects to observe, and to get their rough positions in the sky so we know where to look for them.

For our location and date, the three best stars are Altair, Spica, and Dubhe.

photo of Pub 249, Sight Reduction Tables for Air Navigation with the Rude Star Finder