🔍 Key Concepts

• Use the Nautical Almanac star tables (or star identification tables) for the correct date and hour to find which stars are in the vicinity of your DR position and observed LHA Aries. • Apply all corrections to the observed sextant altitude: index correction, height of eye (dip), and refraction to get an accurate observed altitude (Ho). • Compare the calculated altitude and azimuth (Hc and Zn) for each candidate star with your corrected observed altitude and bearing to see which one matches best.

💭 Think About

• First, carefully convert the chronometer time (with its error) to UTC/GMT and then to GHA Aries and Dec Aries using the Nautical Almanac. What key intermediary angle do you need next to identify a star? • Once you know your DR latitude, LHA Aries, and the date, which tables or sections of the almanac let you list the possible stars near your position and time? How will you narrow these to stars with an azimuth near 019°T? • After applying corrections to hs to get Ho, how can you use sight reduction (or precomputed tables) to see which candidate star gives an Hc close to your Ho and a Zn close to 019°T? What size difference would make a star unlikely?

✅ Before You Answer

• Confirm your time conversion step-by-step: chronometer reading → apply chronometer error → obtain exact UTC used with the almanac. • Double-check your sextant altitude corrections: sign of index correction ("on the arc" vs "off the arc"), correct dip for 45 ft, and the standard refraction correction for stars. • Verify that the computed azimuth of your chosen candidate star is close to 019°T and the Hc vs. Ho difference is small (within a few minutes of arc).